Ying Ding's WebSphere Blog and Study Notes

How to Learn WebSphere in 31 Days - Part Four: A Refresher of UNIX, TCP/IP, and Networking

2011-12-10T17:50:00.000-08:00

In this section, we review UNIX, TCP/IP, and networking topics important to WebSphere system engineering. First, we explain why these topics are critical to a WebSphere system engineer. Then, we will cover these topics as a refresh or review focusing on the topics critical to a WebSphere system engineer in successfully doing his or her job. We assume that you are familiar to UNIX, TCP/IP, and networking. This section is not a systematic coverage of UNIX, TCP/IP, or networking.

UINX, TCP/IP, and networking are important to a WebSphere System Engineer

As a WebSphere engineering manager working in this field for more than ten years, I have hired many WebSphere engineers. When I review the experience and technical skills of a candidate, I focus on the following areas.

Operating System skills, especially UNIX
Networking skills including TCP/IP
Programming skills in Java, UNIX shell scripting, Jython or Python
WebSphere Application Servers skills

A very large number of WebSphere systems run on UNIX platforms. UNIX skills is mandatory for a WebSphere system engineer to perform his or her daily job function. For instance, a WebSphere system engineer has to know the locations of WebSphere system files as well as the locations of JEE applications in a UNIX environment. To access systems and application files and perform WebSphere system operations, you have to know how to identify and manage the security of UNIX systems. Experienced WebSphere system engineers have a script for almost every possible WebSphere system operation, therefore, learning how to program shell scripts (as well as WebSphere automation programs in Jython or Python – we will over this later) and how to schedule and run these scripts as UNIX jobs are imperative to be a competitive WebSphere system engineer. Last, but not least, a WebSphere system engineer, in routine system operations or in problem troubleshooting, must be proficient in using a number of UNIX commands, for example, a UNIX command to determine if there is enough disk space for WebSphere to run.

UNIX topics

First, let's review the following UNIX topics.

UNIX File System – the location of WebSphere system files and JEE application files as well as a review of typical setup of UNIX file system
UNIX Security Model – the topics that are important to WebSphere system engineers
UNIX Commands – a group of UNIX commands frequently used
Shell Scripting – scripting in terms of WebSphere system operation automation

UNIX File System

With UNIX file system and security model, our objective is to identify where are what WebSphere system and application files and how to get access them to get the job done.

As you may recall that the actual locations and names of certain UNIX system files varies with different implementations of UNIX. The following are examples of UNIX system directories:

/bin/ stores executable and common system utilities, like ls, cp, and rm.
/etc/ is the location of system configuration files and databases. For example, crontabs related files are stored here for some UNIX implementation.
/var/spool/cron/crontabs is where Ubuntu keeps the crontab related files.
/usr/bin/ has additional user commands.
/usr/lib/ stores more programming and system call libraries.
/usr/local/ is typically a place where local utilities go.
/usr/man/ keeps the UNIX manual pages.
/opt/IBM/WebSphere is the usual WebSphere directory as recommended by IBM. However, different companies have different enterprise WebSphere system standards that decide where the WebSphere system files should be installed.

Most frequently used WebSphere Application Server directories are listed below. The WebSphere Application Servers system file structure changes some with different releases, but is mainly stable. The following is accurate for WebSphere Application Server 8. The most used are tools, logs files, property files, and configuration files.

The tools are invariably in a bin directory. For example, if you have forgotten your password, you can go to the bin directory and use the following steps to disable security.

First, Go to /opt/IBM/WebSphere/AppServer/profiles/AppSrv01/bin/you can use wsadmin.

Then, type in the following commands, if you use Ubuntu:

sudo ./wsadmin.sh -conntype NONE
securityoff
recycle server

Here is another example, use shell script to start your server in the following directory to start a server.

/opt/IBM/WebSphere/AppServer/profiles/AppSrv01/bin/

If you are working on Ubuntu, use this the following command.

sudo ./startserver.sh server1

While you are starting the server, you can use another windows to traverse into the log directory to monitor the log file to see how well the start of the server is going.

/opt/IBM/WebSphere/AppServer/profiles/AppSrv01/logs/AppSrv01/

You can use the following command, if you use Ubuntu.

sudo ./tail -f startServer.log

For configuration files, you can find them in the following directory.

/opt/IBM/WebSphere/AppServer/profiles/AppSrv01/config/

If you forget your password and username for WebSphere, then you have to modify security.xml file directly to remove security. You can go to the following directory.

/opt/IBM/WebSphere/AppServer/profiles/AppSrv01/config/cells/Node01Cell/

Locate security.xml and open the file in a text editor.
Find the first "enabled" string and change the "true" string to "false".
Then, restart the server without the username and password.

Property files can be found in the following directory.

/opt/IBM/WebSphere/AppServer/profiles/AppSrv01/properties/

wsadmin default scripting language is jacl. Therefore, each time you want to use a script written in Jython, you have to specify the language choice by using the following command if you use Ubuntu (we will talk more about jython and wsadmin later).

Sudo ./wsadmin.sh -lang Jython

However, sometimes you may forget and as a result, your Jython script may not work and the troubeshooting may cost your 15 minutes. You can modify the wsadmin.properties file to make the default language choice Jython.

First, go to the following directory.

/opt/IBM/WebSphere/AppServer/profiles/AppSrv01/properties/

Locate and open wsadmin.properties file using a text editor such as vi.

Find the following line and change jacl with Jython.

com.ibm.ws.scripting.defaultLang=jython

UNIX security and WebSphere

Now let's go over how to set up security to access system and application files and related topics.

User ID and Password

When you join a new WebSphere engineering team, you need to quickly learn how to log into the WebSphere systems and perform your job functions as a WebSphere engineer. You need at least three WebSphere system IDs. You want to apply for these system IDs and understand how to use them to access your WebSphere systems as soon as possible. Because companies manage system access differently, there is always a small learning curve to get over with, even for very experienced WebSphere engineers.

· UNIX system logon ID – this ID is what you use to log into the UNIX servers to run WebSphere Application Server.

o Depending on the information security policy and team structure, this UNIX ID may or may not give you root access. If you work for a company where the WebSphere system engineers play both the roles of UNIX system administrator and WebSphere system administrator, your UNIX ID usually give you root access.

o For the ease of system administration work and the consistency of security policy, your UNIX system ID typically belong to a group that has full system privileges to the WebSphere system files or root access if the WebSphere engineering team is supposed to be their own UNIX system administrator.

· WebSphere Administrative Console ID – this is what you use to access WebSphere administrative console.

o You can disable WebSphere security if you forget this ID or password for the WebSphere administrative console via using wsadmin facility. Then, you can log into the system and enable security.

o Again, your administrative console belongs to a “job code” group that you can apply for to the information security team in order to add your ID. WebSphere logs the activities of this ID.

· WebSphere Application Server ID – this is the UNIX ID that the WebSphere Application Server uses to run in the UNIX environment. Usually, it is wasadmin. Sometimes, this ID is useful and safer when you need to log into the system to work on WebSphere Application Server. This is especially true if you have root access because the use of this ID limits your use of root privileges in case you accidentally make a mistake.

o sudo su – wasadmin

o WebSphere Application Server ID and password are “public information” with the WebSphere engineering team. Therefore, be careful and honest when use this ID to do system work. All companies have software such as PowerBroker that watches every command you use. The monitoring software can trace back to your own UNIX ID for every command that you issue.

o You can use wasadmin and password to launch scripts through wsadmin port from a remote computer. This use of wasadmin application ID is not being traced today. If you see system changes that cannot be explained via auditing system access logs of WebSphere administrative console or UNIX system access auditing logs, this is what is an area of possible root cause to explore.

· In a “security hardened” environment, all security objects such as user name, UNIX system ID, among others, are consistently managed across the enterprise using a directory service, usually a kind of LDAP server. The availability of the LDAP service is therefore not only important to your system access, also it is critical for your WebSphere Application Server.

· If your organization does not give WebSphere engineering team root access, before you perform WebSphere Application Server installation work, usually you need to apply for a temporary root access. The security team will then add you to a group that has a modified set of root privilege to enable you with the installation work. Usually, such root privileges have a time constraint and will be revoked after a time period set by your organization.

· Security software such as PowerBroker for UNIX from BeyondTrust.com records every command that you issue after logging into the system. Frequently, the log file is encrypted and shipped to a secure location beyond your manipulation and modification. In the case of serious accidents when the company sustains heavy losses, this type of log files are retrieved and analyzed to determine what happened.

Frequently used UNIX command

Let's review UNIX commands frequently used by WebSphere system engineers. I group the commands a few functional groups and use Ubuntu as examples. A different UNIX product such as AIX may have different commands. However, it is important to learn how to use this type of commands to do what you need to do as a WebSphere engineer.

Know what WebSphere and Java software are running
New to a WebSphere system, you want to know quickly what are running.

Directory	Ubuntu Command	Purpose	Example
/opt/IBM/WebSphere/AppServer/bin	versionInfo.sh	Determine WebSphere product version	sudo ./versionaInfo.sh
cd/usr/sbin	apachectl –v	Determine Apache web Server version	Sudo ./ apachectl –v
	java	Determine Java vefrsion	java –version
	`ps`	Determine what servers are running	`ps -ef \| grep java`

Know the platform

Frequently, you need to know what platform you are working. To be practical, I list relevant AIX commands as well.

Ubuntu command	Purpose	Ubuntu example	AIX command	AIX example
cat /proc/cpuinfo	View all processors, clock speeds, flags, and more	cat /proc/cpuinfo	prtconf -c	prtconf -c
cat /proc/meminfo	View amount of RAM and swap, and how much is being used for what	cat /proc/meminfo	prtconf -m	prtconf -m
df	View disk space and usage	df -H	df -H	df -H
	Display the kernel in use, for example, 32-bit or 64-bit		prtconf -k	prtconf -k
lshw	Display hardware	sudo lshw	uname	uname -a

Know system performance
You need to know how the system is doing, for example, how the CPU, memory, network, or storage is doing, especially in troubleshooting.

Command	Purpose	Example	Notes
top	Overall system usage by process	top	Some organization disables this command
vmstat	Virtual memory statistics	vmstat -a	You can use switch to select what you need
netstat	The default display for network	netstat -i
ps	Process system usage	ps –ef	Display every process using standard format
df	Disk usage statistics	df –k	Block size – 1K
du	Displays a summary of disk usage	du -a	Display the disk usage of each file
lsof	Information about files opened by processes	lsof	lsof
iostat	I/O statistics	Iostat 1 5	5 reports every 1 second

Work with processes

You sometimes need to identify a WebSphere process and use kill command to either produce dumps or kill the process when it becomes unresponsive.

Command	Purpose	Example	Note
ps –ef \| grep java	Find the process	ps –ef \| grep java	This returns a lot of information on the process.
kill -3 PID	Terminate with core dump	kill -3 13455	13455 is a sample PID
kill -9 PID	Forced termination	kill -9 13455	13455 is a sample PID

Work with log files

To be effective in working with log files, you want to be fluent in one of the editors. If you cannot decide which editor you like, you can try vi that is available with almost all flavors of UNIX.

Command	Purpose	Example	Note
head -number	View n lines of log file from the beginning	head -10 logfile1203.log
tail - number	View n lines of log file from the end	tail -10 logfile1203.log tail -f startServer.log	"tail –f starServer.log" will continuously view the activities in the log file
find	Find the log files	find / -name "*.log" \| -print	Find the log files
Command (vi)	Purpose	Example	Note
/STRING	Search downward in the log file for the STRING	/OutofMemoryEerror	In vi editor, type “/” then, type the string to search
?STRING	Search upward in the log file for the STRING	/OutofMemoryError	In vi editor, type “?” then, type the string to search
n	repeat last search from present position	n	In vi editor, type “n” to repeat the last search
Ctrl-g	Show line number of current line	Ctrl-g
G	Move the cursor to the end of the file	G
Ctrl-b	One page up	Ctrl-b
Ctrl-f	One page down	Ctrl-f

To get more WebSphere related examples, I will delay the discussion of shell scripting and running scripts as cron job later when we have covered some WebSphere topics.

TCP/IP and Networking

WebSphere Application Server provides an execution environment for a JEE application to run on either Internet or Intranet. A typical deployment of WebSphere Application Server is usually integrated with a number of upstream and downstream systems in a network environment connected to the intranet or the Internet or both. Hence comes the need for a WebSphere system engineer to learn networking.

As a typical setup, the web browser communicates with the WebSphere Application Server via geographical load balancer such as 3DNS. 3DNS balances load between data centers. Then, the traffic is load balanced by local load balancers such as BIG 5. The firewalls that form de-militarized zones (DMS) protect the WebSphere Application Server system along with backend enterprise systems. The WebSphere Application Server is integrated with databases using database drivers through network as shown below.

User web browser->

------ Internet ------

Geographical load balancers ->

------- Firewall -------

Local load balancers ->
Web servers ->
------- Firewall -------
WebSphere Application Servers ->
A variety of enterprise systems

To work effectively in this networked WebSphere environment, there is a need to be able to clearly identify HTTP, HTTPS, virtual host, port, SSL, certificate, firewall, load balancer, among others. Let’s take an approach of traversing through each layer of this typical WebSphere architecture and go over the key concepts and skill as we go.

HTTP

I heard of HTTP for the first time in 1993 from a fellow graduate student. She talked about her thesis and told me about HTML document. She was interested in the possibility of using HTML to create computer-based training on the server. I asked her how the students could get to the HTML documents on the server. She mentioned access to the server. Of course, it was till 1995 HTTP gained popularity as a TCP based transport with the introduction of browser. As a WebSphere engineer, you want to be able to identify the following.

HTTP protocol
HTTP session
HTTP port
HTTP status code
What a WebSphere engineer does with HTTP

HTTP protocol

HTTP is a request-response network protocol to deliver files and other data from the server to the client. Usually, HTTP uses socket to deliver resources requested.

HTTP session

HTTP session is a delivery channel established between the server and the client. A sequence of request and response is carried via this channel before the session is destroyed. The HTTP session is needed to overcome the stateless nature of request and response protocol, since it is important to for the server to retain the state of the client and its requests.

HTTP port

The client makes a request to the server and initiatives a TCP connection via a particular port, usually port number 80. The server starts to listen this port for client request. As soon as the server receives a request, it sends back a status line and a message with resource requested as the body.

HTTP status code

The following are the most frequently seen status codes.

200 OK - The request succeeded, and the requested resource is returned.
404 Not Found - The requested resource can’t be found.
301 Moved Permanently
302 Moved Temporarily
303 The resource has moved to another URL
500 Server Error - An unexpected server error has occurred.

What to do with HTTP

A WebSphere system engineer frequently works on the following HTTP related tasks.

o   Configure HTTP server, for example, Apache web server or IBM HTTP Server (HIS)
o   Design and implement the location and the routing of static contents such as HTML documents
o   Configure the TCP/IP transport port of the WebSphere Application Server. For example, you can configure and route traffic directly to the TCP/IP transport port of the WebSphere Application Server
o   Design and implement HTTP session, for example, session persistency and session failover
o   Configure virtual host
o   Troubleshooting HTTP related problems, for example, pinging a HTTP port to see if the web server or the application server’s HTTP port is functional and responsive to requests

HTTPS (TyperText Transfer Protocol Secure)

I started to learn and use Internet security when I was developing Java applications for the now defunct Enron Corporation in Houston as an IBM technical consultant. Enron was trying to sell utilities such as gas and electricity through the Internet to residential and small business by using Internet technologies. One of the technical challenges was to secure the contracts sent to the customer. First, such document should be encrypted against interception. Secondly, the customer should not be able to modify the document. At the first glance, the security task looked intimidating. However, after some time working on Internet and Java security, I successfully used HTTPS to encrypt the transmission and bought a software component from an Australian company to ensure that the customer could not use PDF editor to modify the contract sent to him or her through Internet.

HTTPS is a secure transport

HTTPS is secure HTTP transport. The transmission of data over the Internet is encrypted. HTTPS uses keys to encrypt and descript data transmitted over the network. For encryption, HTTPS depends on Secure Socket Layer (SSL) that is now officially Transport Layer Security (TLS).

TLS or SSL

To discuss TLS or SSL, you first should learn asymmetrical cryptography and symmetrical cryptography. The difference between asymmetrical cryptography and symmetrical cryptography is the key used to encrypt and decrypt the data sent over the network.

For symmetrical cryptography, you can assume the key used to encrypt and decrypt data sent via the network is the same. For example, you can use the same key to decrypt a text that has been encrypted by the same key. It is difficult to use symmetrical cryptography on the Internet, especially for the initial key sharing. Asymmetrical cryptography overcomes this limited by a public key and a private key architecture.

TLS or SLL handshake between the server and the client can appear quite involved There are a number of components involved - the server’s public key, the server’s security certificate, cyphers and hash functions etc. Do not be intimidated. All you need is patience to work through the process. There is an abundance of simple and easy technical explanation to help you to learn, for example, the TLS article by Wikipedia.

The key of TLS is the server’s sharing of public key. The client uses the public key to encrypt the initial exchange to form a session key. The server uses its private key to decrypt the message sent by the client. From then on, ta session key is formed and works as the symmetrical key for security communication.

Please have a look at the following steps (Digital certificate is discussed in the next paragraph).

· The handshake begins when a client connects to a TLS-enabled server requesting a secure connection and presents a list of supported cipher suites (ciphers and hash functions).

· From this list, the server picks the strongest cipher and hash function that it also supports and notifies the client of the decision.

· The server sends back its identification in the form of a digital certificate. The certificate usually contains the server name, the trusted certificate authority (CA) and the server's public encryption key.

· The client may contact the server that issued the certificate (the trusted CA as above) and confirm the validity of the certificate before proceeding.

· In order to generate the session keys used for the secure connection, the client encrypts a random number with the server's public key and sends the result to the server. Only the server should be able to decrypt it, with its private key.

· From the random number, both parties generate key material for encryption and decryption.

Digital Certificate

Your driver’s license can function as a certificate to your identification. Digital certificate, public key certificate, or identity certificate all refer to an electronic document that serves as the proof of the identification of a web site. Your driver’s license may come from your local government. A digital certificate for a web site usually is issued from a Certificate Authority or CA such as VeriSign. There is a variety of digital certificate with different class and different level of protection. For example, the digital certificate used by the Bank of America online banking is a 128-bit certificate that provides strong encryption protection. Depending on the browser that you use, you can see in the address bar of browser having “Bank of America” in green background either on the right side or left side of the address bar. Click on “Bank of America” with green background, you will see details of the 128-bt digital certificate. Examine the certificate and compare Bank of America’s certificate with other large banks and note any difference.

HTTPS port

Often, an IP address uniquely identifies a computer and a port number a unique process on that computer. Therefore, an IP address and a port number constitute a unique end point in network communication.

Here is a list of well-known ports. I was asked about these ports at a job interview. At least, remember that HTTP uses port 80 and HTTPS uses port 443. For a comprehensive listing, check out this Wikipedia article.

· 20 & 21: File Transfer Protocol (FTP)

· 22: Secure Shell (SSH)

· 23: Telnet remote login service

· 25: Simple Mail Transfer Protocol (SMTP)

· 53: Domain Name System (DNS) service

· 80: Hypertext Transfer Protocol (HTTP) used in the World Wide Web

· 110: Post Office Protocol (POP3)

· 443: HTTP Secure (HTTPS)

What a WebSphere engineer does with HTTPS

A WebSphere engineer installs and configure the digital certificate, troubleshoot the certificate and HTTPS related issues, as well as ensure that the digital certificate gets updated before it expires. All these are important work. For example, if your certificate expires before you update the certificate, your production servers may be impacted. However, WebSphere infrastructure design is the main area of work that a WebSphere engineer needs to use his HTTPS knowledge and skills. The following are some of the topics during the design phase of a project.

· Consulting work on whether to use HTTPS – HTTPS secures network communication with a performance cost due to the resources needed for encryption and decryption

· Where to terminate HTTS – within the Intranet of a corporation, there may not be a need for HTTPS and the extra cost. Therefore, the HTTPS traffic comes from the Internet may be terminated at the local load balancer layer

· Decisions on offloading the HTTPS encryption and decryption work form the server in using special equipment or appliances such as dedicated encryption card or IBM Data Power appliance due to the CPU intensive nature of encryption

· Helping the team to identify certificate to use and the Certificate Authority to use

Geographical load balancer

Geographical load balancer is also called global load balancer. It is a specialized computer or a network device that distributes traffic among data centers. Companies that have multiple production data centers usually have 1+N redundancy to achieve high availability and resiliency for critical enterprise applications. Geographical load balancers are deployed at each data center to distribute the load among the clusters of redundant servers. To better understand how a geographical load balancer work, we have to have a look at Domain Name System or DNS.

DNS

Many years back, I got an interesting email. The message was about a beautiful, young, female PhD candidate, a total stranger, reaching out to me for friendship. There was a phone number in the message and I was encouraged to call. I did call and the young lady, a young PhD candidate, did answer my call and told me that I was one among many who called. Someone sent out hundreds of emails in her name and gave out her phone number.

I had a close look at the email header and found the IP address of the computer where the email came from. I looked up the domain name by using the IP address and found the domain name. I found the domain name belongs to a university. I called the university and asked for help to locate the computer. The university IT found that the computer belonged to one of its computer labs. Searching through the lab’s logbook, they identified a male student who used the computer when these messages were sent out from the computer. The authority was notified. The FBI came and took the keyboard, mouse, and the computer as evidence.

Yes, you can get to the domain name from the IP address. The opposite is true as well. You can also, more often, get to the IP address from the domain name. Either way, Domain Name System is involved. A DNS is a primarily a hierarchical distributed naming system for computers. Have a look at the following.

1. A web browser contacts a DNS server with a domain name for IP address

2. If the DNS server does not have this name, it contacts its “parent” DNS server

3. The “parent” DNS server found the domain name and its IP address

4. The IP address is returned to the “child” DNS server

5. The IP address is relayed to the browser by the “child” DNS server

6. The browser uses the IP address returned to contact the host computer

How Geographical Load Balancer works

Geographical load balancer such as F5 Global Traffic Manager (GTM) is deployed at each data center that is being load balanced. For example, if you have three data centers, you will have three geographical load balancer installed – one each data center. However, only one geographical load balancer is playing the Primary DNS role. When certain browser traffic comes, first it goes to the geographical load balancer that serves as the primary DNS. Then, the following usually happens.

1. The primary DNS sends a query to each geographical load balancer

2. The responses are collected and a “best fit” candidate is determined

3. The primary DNS returns the IP address of the “best fit” device

4. The browser uses the IP address returned to contact the device at the right data center

What a WebSphere engineer do with geographical load balancer

Very few IT organizations have their middleware team manage geographical load balancer. However, a WebSphere engineer is better equipped with high-level knowledge of geographical load balancer, especially in designing middleware infrastructure and in isolating an infrastructure problem.

Firewall (under development)

The Function of Firewall

Firewall protects security network from unsecure network such as Internet or business partner’s network.

Firewall technologies

Packet filter firewall (stateless and stateful)

Application level firewall

Next generation firewall (NGFW)

Firewall products

Check Point

Palo Alto

What a WebSphere engineer do with firewalls

Send a request to the firewall team to open a port

Troubleshooting middleware problems – determining where the traffic got stuck

Local load balancer

· Functions

· Technologies

· Products

· What WebSphere engineers need to do with local load balancer

Web Server

· HTML

· Virtual Host

· Bandwidth throttling

· Plugin

Backend

· OS level network

· URL to database

(To be continued)

How to Learn WebSphere in 31 Days - Part Three: A Quick Java and WebSphere Review or Overview

2011-12-06T18:45:00.000-08:00

This is a quick review or overview of Java and WebSphere Application Server to get you prepare for this technical training program of WebSphere. You do not need to have in-depth understanding of all the technologies of Java and WebSphere to be a good WebSphere engineer. However, a basic knowledge helps.

What is Java SE 6 or JSE 6? Can you tell the differences between Java SE 6 and Java EE 6? Is the JRE 6 a synonym of JDK 6? What is the connection between Java technologies and WebSphere Application Server?

Over the years I have seen experienced WebSphere system engineers who cannot confidently answer these questions. I agree that you may never have to directly answer these questions, as a WebSphere system engineer. However, WebSphere Application Serve, from a knowledge acquisition perspective, is an implementation and subset of JEE technology. As a result, if you can identify foundational Java concepts, it significantly helps with your learning of WebSphere Application Server technologies.

For example, if you can identify the technical characteristics of a “stand alone” JVM, you may avoid making a mistake in agreeing to support a Java application that executes in a JVM outside WebSphere Application Server. Many WebSphere engineering organisations specialise in supporting WebSphere systems with containers for JEE applications and may have a policy of not supporting Java applications that run in “stand alone” JVM instances. To be able to follow this policy, you first and foremost have to be able identify a “stand alone” JVM from an application server.

In addition, from a learning perspective, to have a bird eyes view of the WebSphere technologies help speed up the learning of technical details as a kind of “top down” approach.

This chapter will help you identify, as an overview and a refresh, JSE 6, JEE 6, and WebSphere Application Server as a preparation for you to work through the rest of this WebSphere training program.

JDK 6.0

A WebSphere engineer needs to know JDK 6.0 for two practical purposes. Firstly, provide consulting services to the application developers on the new features supported by different version of JDK. Secondly, to identify which JDK is supported by the WebSphere Application Server release under discussion. Different WebSphere Application Server releases may support different JDK releases. The application developers need JDK new feature information to decide which WebSphere release to target as the execution environment. Beside, you need to know the JDK to help with important decision such as WebSphere system upgrade.

Now let’s review Java basics, then, have a look at the new features of JDK 6.0.

Java SE 6 stands for Java Platform Standard Edition 6. This Java platform is also referred to as Java Development Kit, or JDK, that includes three major components.

Java tools and tools API, for example compilers and debuggers
A set of standard libraries of Java API
Java Virtual Machine (JVM) - the execution environment of a Java application

Java Runtime Environment, JRE, has the standard Java API libraries as well as the JVM, but does not include the Java tools or tools API. JRE is a subset of JDK.

JSE 6 is used for developing and executing Java applications on the desktops or on the server as “stand alone” Java applications that does not run within the execution environment provided by an application server such as WebSphere. In addition, a JRE allows Java applets^¹ run within popular browsers.

New features for JDK 6.0

Web Services – Web Service is typically an API that is accessed through HTTP. This is an important technology, especially as a critical building block for Service Oriented Architecture (SOA). You should develop a conceptual, if not technical understanding of Web Services and SOA. JDK 6.0 provides better support for developers get web service client applications. For example, the developer can expose his API as .NET interoperable web services with a simple annotation
Scripting – JDK 6.0 allows the mixing of Java Script technology source code into Java code
Database – JDK 6.0 has a great out-of-the-box development support for database applications, the Java SE 6 development kit – though not the Java Runtime Environment (JRE) – co-bundles the all-Java JDBC database, Java DB
Monitoring and Management – JDK 6.0 adds more monitoring and management tool for diagnostic information as a development aid. For example, JDK 6.0 has memory-heap analysis tool JHat for examining core dumps
Pluggable Annotations – Annotations and Aspect Oriented Programming in a sense extends Java as an Object Oriented language. JDK 6.0 provides better support for annotations

JEE 5.0

You may wonder why we want to learn on JEE 5.0. The answer is simple – this training program focuses on WebSphere Application Server 7 that supports JEE 5.0.

JEE 5.0 is the abbreviation of Java Platform Enterprise Edition 5.0. JEE 5.0 is an industry standard for developing and deploying server-side enterprise applications. JEE 5.0 consists of application programming interfaces (APIs), a set of services, and protocols that provide the functionality of developing web-based applications. In addition, Java EE Compatibility Test Suite (CTS) is provided to test the compatibility of an Application server product.

New features of JEE 5.0

Enterprise JavaBeans 3.0 - EJB 3.0 is one of the most important components of JEE 5 Specification with host of new features and enhancements such as annotation and interceptor.
Java Persistence API providing a POJO based persistence model - now you can use POJO objects to persist into database, its much like hibernate and other ORM tools.
JavaServer Faces 1.2 - JavaServer Faces technology simplifies building user interfaces for JavaServer applications
Web Services Metadata for the Java Platform 1.0 - the web services metadata specification provides a rapid and simple solution to define and develop web services.
Java API for XML-Based Web Services (JAX-WS) 2.0 -
Java Architecture for XML Binding (JAXB) 2.0
Streaming API for XML (StAX) 1.0
Java Web Start technology support - Standalone rich Java applications can be accessed with a single click over the network from Application Server eliminating the need of local client configurations etc.
EL Resolution - The new EL spec allows you to chain, resolution for both variables and properties. Now the variable resolution can be chained with Spring.
SE 5 Support - JEE supports annotations and other features of JSE.

WebSphere Application Server

WebSphere Application Server is the flagship product of IBM WebSphere technologies. WebSphere Application Server is JEE compatible. In addition, WebSphere Application Server confirms open other standards such as XML and Web Services. It works with a variety of web servers, for example, IBM HTTP server.

WebSphere Application Server provides the execution environment for JEE business applications. The application developers do not have to work on the infrastructure aspects such as hardware, operating system, and the network. The WebSphere Application Server also provides the following.

A transaction and messaging engine
Delivering business logic to end-users on a variety of client devices
Serving as middleware between back-end systems and clients
Provides a programming model
An integration point to a variety of applications confirming to SOA reference architecture
Serving as the base for other WebSphere products, such as IBM WebSphere Enterprise Service Bus, WebSphere Process Server, and WebSphere Portal
JEE application security enabling and management
Flexible system management capabilities

1. A Java applet is an applet (small special task application within the context of a larger application) to delivered to the users usually through a Web browser using a Java Virtual Machine (JVM) or Java Runtime Environment (JRE).

2. WAS or WebSphere may also be used to refer to WebSphere Application Server in the rest of this series of discussion.

How to Learn WebSphere in 31 Days - Part Two: Build Your Computers for Learning WebSphere

2011-12-05T16:06:00.000-08:00

Before you can start learning WebSphere technologies, you have to have a set of software and one or tow computers to learn WebSphere.

The software you need are a recent version of WebSphere Application Server and Web Server, the newest release of WebSphere Application Server and Web Server, and an application development environment such as Eclipse.

As far as operating system (OS) and computer goes, you need one or ideally two computers. One of the computer should have a flavour of UNIX installed, maybe LINUX such a Ubuntu. The other computer should be a MS Windows based machine.

WebSphere Application Server license does involve a charge. However, to help professionals and companies to learn and evaluate WebSphere Application Server, IBM usually makes full strength WebSphere Application Server software such as WebSphere Application Server 8 Network Deployment available for trial.

Eclipse is a free downloadable application development environment. Eclipse is good for design and development of automation script for WebSphere Application Server.

Ubuntu is a free open source LINUX operating system. It is quite stable and easy to use while providing a viable platform for you to learn UNIX as well as running WebSphere Application Server on UNIX - this is how most large corporations run their WebSphere software - on a flavour of UNIX such as IBM AIX or Red Hat LINUX. You will find that running WebSphere on LINUX is a bit more challenging than working on MS Windows. However, this is exactly the practice that you need to learn new skills and grow your technical capabilities.

You have two ways of running Ubuntu on your computer. One is to install Ubuntu to your hard drive. The other is to install Ubuntu to a large flash drive. The advantage of installing Ubuntu to a flash drive is that you can use the Windows to run WebSphere for Windows. The disadvantage is that you will be constantly challenged and inconvenienced due to space issues. If it is financially possible, it is advisable to use two computers, for one LINUX such as Ubuntu and the other for Windows. You do have a lot of time to struggle with disk space issues and you do not want to spend your time on coming up with clever ways to deal with limited space. You want to focus on learning WebSphere technologies and become competent and productive in applying WebSphere technologies.

Use this link to download Ubuntu. First use a CD or flash drive to learn how to use Ubuntu before installing Ubuntu to your hard drive.

Now you can go to the IBM free download site to download WebSphere Application Server soft.

Create an IBM ID and password
Download WebSphere Application Server IBM Installation Manager for Trial Products (IIM)
Select Using HTTP Download (I have better luck with this)
Download IIM for for Windows and LINUX respectively

Now you are ready to install WebSphere Application Server. Installing WebSphere software involves the following steps.

Create IBM ID and password
Download the IBM Installation Manager for the right OS
Ready your OS for install- other than to make sure that you have enough memory and disk space. For Ubuntu, you have to do the following or the WebSphere software install will fail

unlink sh
ln-s /bin/bash sh
ls -l sh

Install the WebSphere software

go to the directory where you have downloaded WebSphere software
sudo ./install (Those who use WAS 7 be careful - there is no Launch Pad for WAS 8 - it is replaced by IBM Installation Manager - IIM)
You will see a message saying that your OS (Ubuntu) is not supported. Ignore the message and continue with the installation and WebSphere Application Server 8 will install

Create profiles that is a WebSphere way to create application servers and related JVM instance (we will cover this in details later)
Configure application server
Deploy the JEE application
Verify installation and system readiness for delivery

How to Learn WebSphere in 31 Days - Part One: Introduction

2011-12-04T15:35:00.000-08:00

In the early spring of 2010, I got a call from a relative, a very experienced senior electrical engineer with top notch expertise in chip design. He was laid off. He had tried very hard, but could not land on a chip design job. After a number of discussions and serious research, he decided to learn WebSphere engineering and prepare himself to be a WebSphere system engineer.

Then, I was working for a large financial services company, on my 9^th year as a senior technical manager working in the area of WebSphere engineering. I found that I was having an increasing need to refresh my technical skills as a WebSphere system engineer to be a better job and, to put it candidly, to get ready in case that I was laid off as well.

Fortunately for both of us, after 10 years of phenomenal growth, WebSphere was still a fast growing area that had many job opportunities with respectful salary. However, to successfully compete in the marketplace for that profitable WebSphere system engineer position, we need to learn WebSphere Application Server and WebSphere system engineering quickly.

First, we looked at our technical background. We both had long years of doing a technical job in system administration and technical programming to develop software components or applications. We both had a solid technical education. My friend had a Ph.D in electrical engineering and I had hard core master degree in computer science. We both had good operating system knowledge and skills. We determined that we had the necessary technical background to be trained quickly into marketable WebSphere system engineers while both of us need to learn more of computer network.

Secondly, we concluded that we needed a LINUX based machine to learn and practice what we had learned on WebSphere system engineering and administration along with a Windows based system.

Thirdly, we decided a number of critical areas to focus our learning and technical training. We planned to get this training job done in about three to six months when we would only focused on the most critical areas of knowledge and skills essential to help us to do a real WebSphere system engineer job.

The training tasks are listed below.

Build the servers - choose the computer to use and the operating system to install as well as the building of a computer server as a platform for the reader to use working through the training process
A brief JEE overview – this is a brief review of the key concepts of JEE specification that are relevant to a WebSphere engineer. This also includes a high level introduction of WebSphere. The intent is to be gain a bird eye view of the technology before working on technical details.
UNIX: Architecture, File System, Security Model, and Key Commands – this is a review of UNIX architecture, its security model, and key commands as well as CRON jobs, TCP/IP, and networking - topics that are important to WebSphere system engineer. This is not intended as a comprehensive overview of UNIX operating systems, but only the contents that are needed frequently by a WebSphere system administrator.
Jython and WebSphere Automation –the design, programming and execution automation jobs written in Jython. We want to learn enough script programming to be a competent WebSphere system engineer.
WebSphere architecture and overview – this is an overview of the most recent release WebSphere Application Server. This overview focuses those areas critical to the WebSphere system engineer not all the features or new features. We intend to focus on WebSphere architecture and new features of the current release.
Managing The HTTP Web Server -- (1) The Managed HTTP Web servers versus unmanaged (2) The Plug-In Configuration File (3) Working With The Plug-In (4) Plug-In KeyStore
Installation and migration – we want to learn building new servers, migrating to a new version, applying iFixes and fix patches.
Configuration – this is to learn system configuration both through administrative console and automation.
Administration and JEE application deployment – after working in this area, we want to be able to perform regular system administration jobs through the administrative console and command line
WebSphere security – we want to covers the most frequently performed WebSphere security tasks.
Messaging
High Availability and Workload Management
Performance – we plan to learn performance tuning for problem avoidance and performance enhancement.
Problem determination – this section helps to learn hands-on troubleshooting techniques, strategies, processes, and the use of tools such as Introscope.
Interview and WebSphere certification – we realise that it helps to get a job to study a number of typical interview questions and answers at different levels for intermediate, advanced, and lead positions as well as practical interview strategy.

Early on, we came to see that the key strategy to be successful was to focus on the most critical areas of WebSphere engineering. The IBM WebSphere Application Server is a large set of powerful technologies. The IBM WebSphere documentation has a tremendous amount of information. Nobody has the kind of time and energy to learn all the WebSphere technical details. In addition, we had very limited resources and time available to get on a WebSphere job ASAP. Besides, some of the practices recommended in the WebSphere documentation may not be most frequently used in the real world. For example, almost all companies had custom build scripts to do WebSphere system build – the build process detailed by WebSphere documentation is rarely used in industry practice. We wanted to learn what were the most widely used methods and processes, to be useful WebSphere engineers as quickly as possible.

This “Learning WebSphere in 31 Days” comes from a practical training program that we built for ourselves to compete for WebSphere system administration jobs. It did help us learn WebSphere and to get rewarding WebSphere engineering jobs. For example, I had four WebSphere system engineer offers. The program did help us. We believe that it can help you as well, especially if you are in a situation where you need a systematic approach to learn the WebSphere technologies quickly. Last, but not least, we believe that the training material is a useful technical reference for developing a balanced technical skill set for experienced WebSphere engineers as well.

How to deal with application induced system instability?

2011-11-06T18:03:00.000-08:00

Most of the WebSphere instability is caused by application code defect. However, as WebSphere system engineers, we need to help stabilise the WebSphere system. There are three areas where we can help.

Take appropriate measures to achieve relative stability and help with customer experience
Work with the application team to isolate and fix the defects
Use engineering processes to prevent system instability

To achieve relative stability is possible if you take the right approach. For example, for a high traffic system under heavy load, adding JVM instances is quite often the shortest path to relative stability and help significantly improve customer experience. For a slow memory leak, scheduled recycling of the servers is very effective in achieving a level of stability.

Before you create more JVM instances, you have the following to consider.

Does the application support vertical clustering?
Does the application support horizontal clustering?
Does the application have only limited clustering support?

Some application does not support vertical clustering. Some do not support horizontal clustering. Some do not support clustering at all. The most interestingly, some application only has limited support of clustering due to design strategy, for example, all JVM instances have a cache that depends on frequent interaction with the backend to function. These frequent interation with the database may cause database contention, especially under heavy traffic.

For slow memory leak, increasing heap size, switching to 64 bit systems, as well as more frequent recycle can help with maintain a level of stability and buy time to fix the bugs causing memory leak.
Work closely with the application team, stay away from finger pointing, build a good work relationship with all engineering and application teams, and pro-actively produce dumps and share logs. Teamwork and collaboration will help you to isolate the defects and fix them.

Be very careful in performing changes. Design and implement audit and peer review processes. Diligent and careful system engineering processes help in preventing system from occurring or recurring.

WebSphere eXtreme Scale Installation

2011-04-23T13:47:00.000-07:00

This is a high level task of WebSphere eXtreme Scale installation.

Download WAS binary and decompress the binary
Install WAS
Apply the latest update (fix pack)
Download eXtreme Scale binary
Install WXS
Apply the latest update (fix pack)
Use profile manager to create WAS profiles

Federate notes
Create cluster
Add members to cluster

Use profile manager to create WXS profile (the PMT program will detect the WXS installed and provides the profile choice for WXS
Configure WXS

Of course, you want to 1) have X-Window Server if you are running windows, 2) choose to use ssh to tunnel to the server rather than telnet.

Install WebSphere eXtreme Scale installation 7.1

2011-04-13T04:35:00.000-07:00

In general, a topology design, software and hardware systems consistent to IBM system requirements, and capacity planning, build and configuration specification should be in place before build activiy can start.

Stand Alone

stopManager, stopNode, stopServer (these processes must be stopped or the results can be unpredictable
make sure that JAVA_HOME is properly defined
uninstall the previous WXS installation
install WXS
verify installation

With WAS

decide on full installation or client installation
install WAS
apply WAS a proper version of fix packs
stop the Java processes
uninstall the previous WXS installation
install WXS
verify installatin

Reference: WXS system requirements,

WebSphere eXtreme Scale - Basic Components

2011-04-10T10:41:00.000-07:00

Map -
A map is a container for key-value pairs, which allows an application to store a value indexed by a key. A map set is a collection of maps with a common partitioning algorithm. A map set can have a schema associated with it. A schema is the metadata that describes the relationships between each map when using homogeneous Object types or entities.

Container Server -

"The container server stores application data for the data grid. This data is generally broken into parts, which are called partitions, which are hosted across multiple container servers. Each container server in turn hosts a subset of the complete data. A JVM might host one or more container servers and each container server can host multiple shards." - IBM Documentation

Parition -

"Partitions host a subset of the data in the grid. WebSphere eXtreme Scale automatically places multiple partitions in a single container server and spreads the partitions out as more container servers become available." - IBM Documentation

Shards -

Shards are instances of partitions and have one of two roles: primary or replica. The primary shard and its replicas make up the physical manifestation of the partition.

Clients -

Clients connect to a catalog service, retrieve a description of the server topology, and communicate directly to each server as needed. This is the application that uses the WXS data and services.

Catalog service -

Locatin service - "traffic cop" - "google map" guidance for traffic from client to container and from container to client

Placement service - "The placement service is the central nervous system for the grid and is responsible for allocating individual shards to their host container." - IBM Documentation

Core Group Management -
This is the same as WAS core group - the manager manages peer grouping for health onitoring, organizes containers into small groups of servers, and automatically federates the groups of servers.

WebSphere eXtreme Scale Write-Behind Considerations

2011-04-10T08:31:00.000-07:00

Transacation mangament -
For write behind, the transaction management is decoupled between the ObjectGrid and the database with the ObjectGrid finishes before the database. Otherwise, without the wirte behind enabled, the ObjectGrid transation encloses the database transations.

Referential integrity constraints -
The backing map configured with write behind can have concurrent threads updating database backends. Therefore, when designing database referrential contraints, out-of-order updates should be allowed.

WebSphere eXtreme Scale is all about cache, but what cache?

2011-04-10T04:37:00.004-07:00

Spare cache - only keeps a subset of the data
Complete cache - keeps all the data
Side cache - provide read and query performance as a temparory storage in parallel to the database. This is better than the regular cache because it has automatically replication capability between all processes
In-line cache - works between the application and the database through a backend load plug-in. In-line allows the application using WXS API to do
a. read through
b. write through
c. write behind

Webpshere eXtreme Scale Planning

2011-04-09T19:53:00.000-07:00

Install catalog server and container server on different physical machines

better performance
easier and separate upgrade

Your installation must support your design

the topology
caching strategy

What to do with WebSphere eXtreme Scale?

2011-04-09T13:51:00.000-07:00

Start a core group
Start a catalog service
Start WebSphere eXtreme Scale servers (The servers register with core group and catalog service coordinates the provisioning of data)
Decide to install local grid or distributed grid through planning

What is WebSphere eXtreme Scale (WXS)

2011-04-09T09:48:00.000-07:00

"WebSphere eXtreme Scale is an elastic, scalable, in-memory data grid. It dynamically caches, partitions, replicates, and manages application data and business logic across multiple servers.r" - IBM documentation

WXS is dynamic

It can dynamically create new servers and remove the number of servers
It can add or reduce the network throughput on the fly
It is self-healing (autonomic) and can recover from failures

It has partitions of data

It has partition (shards) to spread out the data across servers
It has replication of these shards against failure
It has data structure (catalog) and special SQL support to the operations and management of these partitions (shards)

It is a write-behind cache that serves as a front-end cache for the database backends
The data grid can be run from hundreds of JVM instances and therefore very large
The data grid can be hardened using disk files or database or both
Data grid is a key-value pair for data storage and retrieval

What is NOT WebSphere eXtreme Scale?

It is not an in-memory database - in-memory database is not as resilient aand high performance as WXS
It is not an object-relationship mapper (in other words, database and data grid consistency must be maintained by the application or the mapper)

UNIX privilleged and well known ports, a list of signals, and other UNIX stuff

2011-04-04T18:36:00.000-07:00

The knowledge of these port numbers might come handy or at least is good knowledge: Unix well known ports .

Another very good article on port scan: Port Scan and frequently used ports.

“An ephemeral (short-lived) port is a transport protocol port for Internet Protocol (IP) communications allocated automatically from a predefined range by the TCP/IP stack software.” - Wiki - these are non-privileged ports are assigned to a process dynamically. The key is that it is a range of ports and the range is different from OS to OS.

Before we leave this topic, let's share this article on arp and mac address - article on arp and mac address.

Unless you have been writing IPC code that uses system calls to the kernal, you perhaps have not come across signals. However, a knowledge of the signal may help you deepen your understanding. For example, when you issue a kill -9 command, you are asking the kernal to send a SIGKILL to the process that you want to termniate. Here is the the list of sginals from Wiki. Wiki on Signals

Good article on Dynamic Cache

2011-04-04T07:07:00.001-07:00

A good IBM article on Dynamic Cache - if you do not want OOM, read this article.

Do you know which process is using what port?

2011-04-02T16:56:00.000-07:00

In case you have a port conflict - that is a process is already using a port. How do you know which process is using what port?

You can download, install, and use lsof.

Here is the link on how use it - How to use lsof.
Here is the link to download the program for LINUX - Download lsof program.

Session Affinity

2011-04-02T10:47:00.000-07:00

"JSESSIONID Cookie Format - In a clustered environment, the JSESSIONID cookie is composed of the core Session ID and a few other components. Here's an example:

Cache ID
Session ID
seperator
Clone ID or Partition ID

A Partition ID is appended to the cookie if memory-to-memory replication in peer-to-peer mode is utilized for Distributed Session management. Otherwise, a Clone ID is appended.

Session Affinity and Failover
The Clone/Partition ID corresponds to whichever cluster member creates the Session, and the plug-in is responsible to send that session to the same cluster member as long as it is available. From the Scalability Redbook: "Since the Servlet 2.3 specification, as implemented by WebSphere Application Server V5.0 and higher, only a single cluster member may control/access a given Session at a time. After a Session has been created, all following requests need to go to the same application server that created the Session. This Session affinity is provided by the plug-in. If on a subsequent request the specified cluster member is unavailable, the plug-in will choose another cluster member and attempt to connect to that. If Distributed Sessions are configured, via database persistence or memory-to-memory replication, the Session will be resumed in-progress on that new member. If not, a new Session will be created and the user's progress will be lost."

If a new cluster member is able to resume the existing Session, it will append its own Clone/Partition ID to the existing JSESSIONID cookie. For instance:

JSESSIONID=0000A2MB4IJozU_VM8IffsMNfdR:v544d0o0:v544d031

Now the plug-in knows that two different cluster members could potentially service this Session. If the original member becomes available again, the Session will switch back to it. Finally, note that according to the System Management Redbook: WebSphere provides session affinity on a best-effort basis. There are narrow windows where session affinity fails. These windows are:

When a cluster member is recovering from a crash, a window exists where
concurrent requests for the same session could end up in different cluster
members

A server overload can cause requests belonging to the same session to
go to different cluster members"

The above is reformatted of the following IBM link: IBM Developer Article on JSESSIONID and WAS Session Management

The following link is an IBM Infocenter article to configure ODR for WebSphere Virual Enterprise. Configure ODR for Session Afinity - you do not normally have to do this unless for the reasons mentioned in the document.

Sunil Partil has a good and concise article in his WebSphere Notes - Session Management - it points out in a clustered environment how the web server plugin use clone ID or partition ID to ensure session affinity.

One Way or Two Way Encription

2011-04-02T10:14:00.000-07:00

"SSL provides secure connections by allowing two applications connectingover a network connection to authenticate each other's identity. Additionally, SSL provides encryption of the data exchanged between the applications. Authentication allows a server (one-way) and optionally a client (two-way) to verify the identity of the application on the other end of a network connection. Encryption makes data transmitted over the network intelligible only to the intended recipient.
Features of SSL include the following concepts:

SSL provides a mechanism for one application to authenticate itself to another application.
One-way SSL allows one application to be certain of the identity of the other application.
Two-way SSL (mutual authentication) allows both applications to be certain of the identity of each other.
The application that assumes the "server" role possesses and uses a server-side certificate to prove its identity to the client application.
In mutual authentication, the application that assumes the "client" role possesses and uses a client-side certificate to prove its identity to the server application.
The application that is presented with a certificate must have in its possession the root certificate (or certificate chain) of the CertificateAuthority (CA) that signed the certificate being presented. The root CA certificate, or chain, validates the certificate being presented.
In client connections, the client browser alerts the user when presented with a certificate that is not issued by a recognized Certificate Authority.

Private keys, digital certificates, and trusted Certificate Authorities can be used to establish and verify the identity of network applications. SSL uses public key encryption technology for authentication. In public key encryption, a public key and a private key are generated for an application.The keys are related such that data encrypted with the public key can only be decrypted using the corresponding private key. Similarly, the data encrypted with the private key can only be decrypted using the corresponding publickey. The private key is carefully protected so that only the owner can decrypt messages that were encrypted using the public key. The public key is embedded into a digital certificate with additional informationdescribing the owner of the public key, such as name, street address, and e-mail address. A private key and digital certificate provide identity for the application. The data embedded in a digital certificate is verified by a trusted CertificateAuthority (CA) and digitally signed with the Certificate Authority's digital certificate. Well-known Certificate Authorities include Verisign and Entrust.net. A trusted Certificate Authority establishes trust for an application
An application participating in an SSL connection is authenticated when the other party evaluates and accepts their digital certificate. A digital certificate used to authenticate is validated by an associated root CA certificate located on the receiving application. Web browsers, servers, and other SSL-enabled applications generally acceptas genuine any digital certificate that is signed by a trusted Certificate Authority and is otherwise valid. For example, a digital certificate can be invalidated because it has expired or the digital certificate of the Certificate Authority used to sign it expired. A server certificate can be invalidatedif the host name in the digital certificate of the server does not match the host name specified by the client." - IBM Tivoli

WebSphere Job Interview Sample Questions 003

2011-04-02T07:14:00.000-07:00

Which one of the following profile related tasks can only be performed using the manageprofiles commandline facility?
A. Delete a profile
B. Secure a profile
C. Federate a profile
D. Update profile templates
Answer: A

A system administrator has successfully installed WebSphere Application Server V7.0 and has run the Installation Verification Tool (IVT) with a success message. Which additional step can be taken to further verify the installation?
A. Check to see if the InstallShield application will run again.
B. Check to see if the installation directory specified exists in the file system.
C. Use a browser to access the launch page of the IBM HTTP Server.
D. Use a browser to access the administrative console and log in successfully.
Answer: D

In order to verify that a server has started successfully and all of its components have initialized without throwing any exceptions, what steps should an administrator perform?
A. Use the Log Analyzer to view the servers activity.log file.
B. View the servers startServer.log and native_stdout.log files.
C. Examine the SystemOut.log file for the current server process.
D. Log in to the administrative console and examine the runtime messages.
Answer: C

An application server is hung and has to be killed and restarted by the administrator. In order to troubleshoot the server hang problem, the administrator decides to reproduce the hang condition and trigger thread dumps for further analysis. What is the most effective way to collect the thread dump data?
A. Trigger one thread dump before and one thread dump after the server restart.
B. Take three consecutive thread dumps 10 seconds apart immediately after the server restart.
C. After server restart wait for the thread monitor to create the first thread dump, then take two more.
D. Wait for the thread monitor to signal a possible hung thread, then take three thread dumps several seconds apart.
Answer: D

Data replication service (DRS) is turned on for replicating in-memory data among WebSphere processes. During peak load, the developer found an OutOfMemoryError in the log. The developer suggests turning off data replication service (DRS).
What services would be impacted?
A. Stateful session EJB persistence and failover.
B. HTTP session persistence and failover.
C. JDBC data source failover.
D. Dynamic cache replication.
E. JVM in memory replication and failover.
Answer: ABD

An administrator has enabled security auditing for the WebSphere Application Server. They wish to view the audit records in order to verify that it is working properly. Which tool would best allow them to view the audit data?
A. IBM Support Assistant using the AuditLogReporter tool
B. wsadmin, using the AdminTask.binaryAuditLogReader command
C. The administrative console - they could invoke the Tivoli Audit Viewer (TAV)
D. The LogAna|yzer from within the Rational Application Developer Assembly and Deploy Tool.
Answer: B

What must an administrator do before he can create method permissions for an Enterprise JavaBean?
A. Map role to groups.
B. Define one or more security roles.
C. Map logical role name to runtime rule.
D. Exclude a set of EJB methods from access.
Answer: B

A federated cell has two nodes, Node01 and NodeO2. Global Security is turned on and is using a file based user registry. Node01 has servers A, B, C and D. A developer has deployed a new security check-in application to servers A and D. As a security requirement, this new application is required to use local operating system registry for user authentications. Identify which one of the following is the most direct way to enable this secured application.
A. Migrate user information from operating system registry to LDAP registry.
B. Create a security domain and scope it to application server A and D.
C. Update global security configuration file security.xml with operating system registry definition.
D. Merge operating system registry and file based user registry to a new LDAP and assign the new LDAP to the federated cell.
Answer: B

In a test cell which has WebSphere global security disabled, an administrator has created a service integration bus (SIBus) with security enabled for testing applications that use messaging resources. Now the administrator needs to enable security on the bus for further testing. Which of the following tasks must be performed to enable security on the bus?
A. Enable administrative security for the cell.
B. Configure a separate security domain for the bus.
C. Delete the bus and recreate it with security enabled.
D. Require messaging clients to use SSL protected transpor1s.
Answer: A

The application accesses an external resource using a J2C adaptor. The security credential for the external resource authentication has changed. Which one of the following should be updated?
A. J2C authentication data.
B. Key stores and certificates.
C. Web security trust association.
D. JAAS login module in WebSphere.
Answer: A

An administrator needs to set up a new employee with administrative access to an existing WebSphere cell. What administrative security roles must the administrator have in order to grant the new employee operator access'?
A. The operator role is required to assign another administrator operator access.
B. The administrator must have administrator role access in order to make the new administrator an operator.
C. The administrator must be the primary administrative user in order to grant security roles to new administrators.
D. The Admin Security Manager role is required so that the administrator can assign new users to administrative roles.
Answer: D

In addition to the normal process for assembling an application, which one of the following tasks must be performed if the EAR file contains a Web services-enabled module?
A. Generate EJB resource mappings.
B. Generate deployment code for the application.
C. Redefine the bindings properties.
D Edit the annotations or deployment descriptors.
Answer: B

Which action below must be performed to ensure that requests routed through the Web server can reach a Web application deployed in WebSphere Application Server Network Deployment V7.0?
A. Security is enabled on the administrative console.
B. An updated plugin-cfg.xml is generated and propagated to the Web server.
C. The Web server and the WebSphere Application Server must be installed on the same physical sewer.
D. The Web server plug-in and the WebSphere Application Server must be installed on the same physical server.
Answer: B

What is the correct console command to execute a wsadmin script file in WebSphere Application Sewer, ND, V7.O?
A. wsadmin -f
B. wsadmin
C. wsadmin /file:
D. wsadmin @executeScript (script file will be prompted)
Answer: A

To use a messager driven bean (MDB) to communicate with the default messaging provider, the administrator must create which one of the following?
A. JDBC provider
B. JCA resource adapter
C. JMS connection factory
D. JMS activation specification
Answer: D

In a Java EE application, how are EJB resources protected?
A. Security constraints
B. Method permissions
C. Java 2 security policy files
D. Administrative permissions
Answer: B

An application which uses JMS clients will be deployed to a stand--alone application server. Messages will be produced by a session EJB and consumed by a message-driven bean (MDB) via a queue destination. What JMS resources must be configured by an administrator to support this application?
A. Destination, queue point, mediation
B. Destination, connection factory, data store
C. Message points, destination, connection factory
D. Queue, connection factory, activation specification
Answer: D

When an administrator creates a service integration bus (SIBus) destination, which one of the following tasks must be performed?
A. Scope the bus destination to a specific cluster.
B. Assign the destination to a specific bus member.
C. Select an appropriate mediation for the bus destination.
D. Create the appropriate message point for the bus destination.
Answer: B

If a deployed application is mapped to a Web server, an updated plug-in configuration file must be generated and propagated. By viewing the plug-in configuration file, how can an administrator determine if the mapping was successful? There will be a:
A. Property element under Transport with a Name attribute equal to the path of the mapped application.
B. URI element under UriGroup With a Name attribute equal to the context root of the mapped application.
C. Server element under ServerCluster with a Name attribute equal to the .ear file of the mapped application.
D. VirtualHost element under VirtualHostGroup with a Name attribute equal to the assigned port number of the mapped application.
Answer: B

When adding a new member to a cluster, why is it necessary for an administrator to select the option for generating unique HTTP ports?
A. To enable encryption over the secure HTTP ports
B. To prevent other applications from using these ports
C. To avoid port conflicts with other servers on the same node
D. To ensure that cluster members on different hosts have unique ports
Answer: C

Aside from the administrative console and the addNode command, what other facilities does WebSphere Application Server provide for federating nodes into cells?
A. wsadmin
B. The administrative agent
C. The Profile Management Tool (PMT)
D. Rational Application Developer Assembly and Deploy Module
Answer: C

A cluster, Cluster1, contains application servers Server1 and Server2. Cluster1 is configured as a member of service integration bus (SIBus). Bus1 using the High availability messaging engine policy. A messaging engine (ME) for Busl starts up on Server1, then Server1 crashes. An ME for Busl will:
A. already be running on Server2. When Server1 recovers, an ME for Busl will start on Server1.
B. start on Server2. When Server1 recovers, a second ME for Busl will start on Server1.
C. start on Server2 but fail back to Server1 after Server1 has recovered.
D. start on Server2 and continue running on Server2 even after Server1 has recovered.
Answer: D

An administrator has created a cluster, C1, and configured memory-to-memory HTTP session replication. How can the administrator best ensure that every HTTP session is replicated on all members of the cluster?
A. In the Replication domain settings for the C1 replication domain, set Number of replicas to entire domain
B. In the Replication domain settings for the C1 replication domain, set Number of replicas to 0
C. In the Memory--to-memory replication settings for each member of C1, set Number of replicas to entire domain
D. In the Memory--to-memory replication settings for each member of C1, check Replicate to all members
Answer: A

A J2EE application maintains information in the HTTP session in memory. This information can be recreated, but there is a performance penalty to restore state if a user session fails over to a different cluster member. Which of the following features maximizes the use of information already stored in a server`s session?
A. Database persistence
B. Session affinity in Web server plugin
C. Memory--to-memory replication in Both Mode
D. Memory--to-memory replication in Server Mode
Answer: B

An administrator wishes to control an Apache Web server on a remote host via the WebSphere Application Server Network Deployment administrative console. What must be done to accomplish this?
A. Configure a web server definition in the administrative console.
B. Configure the Apache administrative process on the remote node.
C. Configure an unmanaged node definition in the administrative console.
D. Configure a managed node on the remote host.
Answer: AD

A cluster, Cluster1, contains two servers, Serverl and Server2. Server1 has a weight of 20 and Server2 has a weight of 4. A single web server is used to route HTTP requests to Cluster1. The web server is started and receives 4 HTTP requests for an application deployed on Cluster1. If the requests are all part of the same HTTP session, and the first request is routed to Server2, how many requests are routed to Server1?
A. O
B. 1
C. 2
D. 3
Answer: A

What does backupConfig back up?
A. Log files
B. Profile configuration
C. WebSphere binaries
D. First failure data capture (FFDC) directory
Answer: B

Where can an administrator find binding information for an application?
A. In the IBM extension file
B. In the activation specification
C. In the deployment descriptors
D. Executing the wsadmin command AdminApp.viewBindings (-ApplicationName)
Answer: C

To install fix packs to remote hosts using the Centralized Installation Manager (CIM), the administrator must download the update installer for the appropriate platforms into:
A. a directory on the class path of a Node Agent on each remote host.
B. the WebSphere Application Server Network Deployment cells CIM repository.
C. the maintenance sub-directory of the application server install on each remote host.
D. the maintenance sub-directory of the profile root of the node hosting the CIM repository.
Answer: B

What is the sequence of components which would typically be involved in the flow of a request from a Web browser to a servlet?
A. External HTTP Server, HTTP Server Plug-in and EJB Container
B. Load Balancer, Embedded HTTP Server, HTTP Server Plug-in and Web Container
C. Edge Component, HTTP Server Plug-in, external HTTP Server, and Web Container
D. External HTTP Server, HTTP Server Plug-in, embedded HTTP Server and Web Container
Answer: D

A system administrator wants to improve response time and system load of a Web application running in a clustered environment. What might the system administrator attempt to decrease the response time of the Web application?
A. Configure dynamic caching
B. Enable memory-to-memory replication
C. Configure session replication to use a database.
D. Ensure that all cluster members are in the same node group.
Answer: A

How could an administrator manage multiple stand-alone application servers on different hosts in a network? By using:
A. a job manager which administers multiple application server nodes through administrative agents.
B. a deployment manager which administers multiple application server nodes through their node agents.
C. a high availability manager which administers multiple application server nodes through their administrative agents.
D an administrative agent which administers multiple application server nodes through their administrative service.
Answer: A

What are the three possible replication types for the dynamic caching service?
A. Client mode
B. Server mode
C. Not shared
D. Push only
E. Both push and pull
F. Broadcast mode
Answer: CDE

Which of the following statements most accurately describes the relationship between a flexible management topology and the network deployment cell?
A. Flexible management can be an alternative to the network deployment cell model.
B. Flexible management eliminates the need for node agents in a network deployment cell.
C. The flexible management topology is a replacement for the network deployment cell.
D. The flexible management job manager can perform all the tasks of the deployment manager.
Answer: A

Interview Tips

Be prepared

Go over your resume one more time, especially if a consulting company has helped improving your resume
In each area of key competence, prepare to talk about your skills including one or two examples of using a skill
Review key WebSphere concepts and terminologies, for example, dynamic cluster

Speak clearly and concisely, if needed, slowly

Speak clearly and make sure that you are understood
Be concise and be crispy. Say it once, and say it powerfully. Do not let wordiness make your interview performance suffer
If you feel that the phone line is not clear enough etc, slow down and make sure that the hiring manager does not have to struggle to understand you
Ask the hiring manager if you need to speak slowly and clearly

Do not let a technical discussion become an argument and competition of ego. Be honest, be respectful, and be professional

Be respectful - years back, I argued with a senior software engineer at a top technology company about a difficult memory management detail before his manager during an interview. You know what happened then
Be professional - even if you feel the technical questions asked are not what you expect, try to answer. For example, I was asked about database joint while interviewing for a middleware engineer position. It is common for companies to evaluate your background in computer science
Be honest - there is nothing wrong to say that "I do not know. But given an opportunity, this is something I would like to learn". Do not try to talk about something that you do not know. It is a waste of your time and it is irritating to the hiring manager

Listen carefully

Listen carefully to understand the question
Do not hesitate to ask for more details about a question if needed
Do not interrupt but listen patiently
Take notes if needed

Ask for feedback and take the interview as a learning opportunity

You can and should ask for feedback on your interview
You can choose to ask for feedback immediately

Ask the hiring manager if you can take a short moment and ask for feedback
How you were doing on the interview
Where you could make improvement in your technical skills
Any other improvements possible, for example, listening or being easy to be understood

You can also ask for feedback from the HR representative whom you have worked with to set up the interview
You can ask the HR representative if it is possible to get feedback on the interview so that the hiring manager is prepared to take notes and provide feedback

Prepare two or three questions (that you are genuinely interested in) about the position, the team, or the company - asking about new technology strategy can be a good topic to get the hiring manager talking.

WebSphere Job Interview Sample Questions 002

2011-03-31T13:36:00.000-07:00

Intermediate Questions

1. Please talk about your recent WebSphere work experience?

Worked on WebSphere 8
Worked on WebSphere eXtreme Scale 7.1
worked on the streamlining and stabilizing of a very large financial WebSphere system
worked on the troubleshooting of a WebSphere Virtual Enterprise system

2. Why do you think that you can be a good WebSphere engineer?

UNIX experience
Good scripting expertise
C, C++, Java language programming
Long years of working on a variety of releases of WebSphere
Long years of working on large and complex WebSphere projects

3. Please explain the major differences between WebSphere 6 and WebSphere 7?

new features in WAS V7

* support Java SE 6
* Java annotation and injection support to reduce complexity
* Web services specification updates
* Flexible management model with Administrative Agent and Job Manager
* Manage DataPower through administrative console
* Properties file based configuration
* Fine-grained administrative security extended to administrative console
* Multiple security domain support
* Security auditing support
* Integration with MQ WebSphere V7 using JCA 1.5 resoure adapter
* Centralized Installation Manager (CIM)
* Rational Application Developer for WAS V7.5

4. Can you tell the major differences between Type 2 JDBC driver and Type 4 JDBC driver?
Type 2 Driver - Native-API Driver specification schematic of the Native API driver. The JDBC type 2 driver, also known as the Native-API driver, is a database driver implementation that uses the client-side libraries of the database. The driver converts JDBC method calls into native calls of the database API. The type 2 driver is not written entirely in Java as it interfaces with non-Java code that makes the final database calls. The driver is compiled for use with the particular operating system. For platform interoperability, the Type 4 driver, being a full-Java implementation, is preferred over this driver. However the type 2 driver provides more functionality and better performance than the type 1 driver as it does not have the overhead of the additional ODBC function calls.

Advantages

* Better performance than Type 1 Driver (JDBC-ODBC bridge).
* Provides Fastest performance than all 3 drivers as it calls native APIs(MySQL,Oracle...etc).

Disadvantages

* The vendor client library needs to be installed on the client machine.
* Cannot be used in web-based application due to the client side software needed.
* Not all databases have a client side library
* This driver is platform dependent
* This driver supports all java applications except Applets

Type 4 Driver - Native-Protocol Driver, Schematic of the Native-Protocol driver
The JDBC type 4 driver, also known as the Direct to Database Pure Java Driver, is a database driver implementation that converts JDBC calls directly into the vendor-specific database protocol. The type 4 driver is written completely in Java and is hence platform independent. It is installed inside the Java Virtual Machine of the client. It provides better performance over the type 1 and 2 drivers as it does not have the overhead of conversion of calls into ODBC or database API calls. Unlike the type 3 drivers, it does not need associated software to work. As the database protocol is vendor-specific, separate drivers, usually vendor-supplied, need to be used to connect to different databases.

Advantages

* These drivers don't translate the requests into an intermediary format (such as ODBC), nor do they need a middleware layer to service requests. Thus the performance may be considerably improved.
* All aspects of the application to database connection can be managed within the JVM; this can facilitate easier debugging.

Disadvantage

* At client side, a separate driver is needed for each database.

5. What is the major function of Job Manager?

* New profile type to support flexible management
* Use administrative agent to register base server profiles with a job manager
* To manage multiple cells, register deployment managers with job manager directly
* Use job manager to queue jobs for registered profiles
* Registered profiles retain autonomy and can be managed without the job manager
* Scales to support large number of registered profiles

6. What are the major new features of JDK 1.5 GC?

*Annotation not deployment descriptor
*GC - more options available such as nursery and tenured sections
*JPA support - no more EJB entity bean (Thank God)

7. What are the major benefits of database connection pool?
A connection pool is a service provided by an application server that can be used to improve data access performance with a group of open connections to the database being maintained persistently. Each time an application needs access to the database, it takes a connection from the pool, access the database then returns the connection to the pool. The connection pool technique removes the overhead incurred when the connection is open and closed. Such overhead can be extremely high for an internet application, which could have a massive negative impact on web applications performance.

8. How do you configure JMS?
Java Messaging Service (JMS) is the standard API for accessing enterprise messaging systems from Java-based applications. It provides methods and functions that are directly implemented by the underlying messaging provider. WebSphere MQ is the premier messaging middleware provided by IBM.

Configure JMS resources

* Create JMS provider
* Create JMS connection factory
* Create JMS queue or topic
* Create listener port
* Create JMS activation specification

9. How to produce a heap dump? How to direct heap dump to a specific location?

kill -3
The dumps go to the working directory.

10.What UNIX commands can be used to find CPU usage or memory usage or network state?

top
topas
ps
vmstat
netstat

11.How do you tell disk usage?
This sounds simple, but I have seen WebSphere consultants did not know what to do when WAS did not start due to 100% disk usage.

df -k
du -k

12.How to configure Introscope 8.1?

*install Introscope agent on the app server
*define Java general argument that includes a profile file that tells where is the Introscope EM along with other relevant information such as port number - the profile file is on the app server - the path has to be included
*create custom service on the WebSphere server via admin console - this specifies the Introscope class
*modify the PBD files to specify metrics to monitor  IBM document on setting up the PBD.

1. A URL is not working. How do you find out why?
First, I would exclude 3DNS and BIG IP by directing trying to get to the URL to the web server transport port. Then, I would try to see if the WebSphere Application Server's port for this URL is working. The key is to determine if the request has ever made to the web layer and application server layer. That is the important first step.

It helps to test all the way from the browser if the network connectivity is working.

For static pages, focus on the web server by examining the access log and error log of the web server. Determine if the web server in general is functional. Web Server resources are adequate.

For application server, examine web container thread, JVM GC, and look at log files for tell-tale message.

Produce dumps (thread, heap, core) and examine these dumps while sending them to IBM with the opening of a PMR.

2. Some users are experiencing latency. How do you find out why?
In the event that some users are experiencing latency or slow response time we should examine the complete request processing chain involving network, load balancers, HTTP web servers, application servers, back end databases, and hardware.

First we examine the network layer such as firewalls or switches and so on to make sure they work properly. Network devices have processing capacity and use memory much like any other hardware resource. Adding additional hardware resources to a network device will increase the throughput.

Then we can investigate load balancers and HTTP web servers to see whether they are over loaded or not. If yes, the web server plug-in tuning might be needed.

The next step is to examine the processing time of application servers at JVM, Web Container and EJB Container layer. For example, check the JVM heap utilization. If GC is too frequent or if the pause is too, then, tune GC.

And finally, the connection pool usage between application servers and backend data sources such as database should be checked. If the database backend is slow, the whole system will be slow. It helps to examine the network connection from the WebSphere Application Server to the database backend and if the database is working as designed.

3. What are the major benefits of vertical clustering and horizontal clustering?
Vertical clustering (process redundancy) involves creating multiple application server processes on a single physical machine, providing application server failover as well as load balancing across multiple application servers. This topology does not provide an efficient fault tolerance because a failure of the operation system or the hardware on the physical machine itself might cause problems to all servers in the cluster.

Horizontal clustering (process and hardware redundancy) involves creating application servers on multiple machines to take advantage of the additional processing capacity available on each machine. Using horizontal scaling techniques also provides hardware failover support.

4. If you add substantial more vertical clustering trying to overcome a bottleneck at the web container layer, what you have to watch out for as a potential system capacity issue?
The first concern is to watch the system memory capacity since the vertical clustering involves multiple JVMs running on a single physical machine and each JVM requires enough memory to achieve desired performance. The memory requirement is heightened even more if the clustering is
configured using servlet and JSP caching in at the web container layer.

Next we should investigate if enough messaging resources are in place to support the heavy communication traffic and loading to the database servers and other enterprise information systems. Throughput and response time under heavy web requests originated from the web servers must be measured to ensure that the vertical clustering meets the expectations.

5. What are some of the application code logic and construct that prevents the use of vertical and horizontal clustering?
Unique counters, traffic routers, and any Java artifacts that depends on a unique serialized valued to perform its business function. This type of the problems can be avoided if the WebSphere engineer engages early in the JEE project and provide WebSphere application development best practices to the application developers and architects.

6. Explain the main improvements of Java 6
1. improved caching capability - shared cache among JVM - caching more Java objectis than static classes - persist Java objects
2. 64 bit reference pointer compression to prevent performance penalty using 64 bit poniters
3. JIT more complied code for better performance

WebSphere Virtual Enterprise questions

1. Can you explain the main features of WebSphere Virtual Enterprise (WVE)?

*dynamic resource allocation through ODR, dynamic cluster, and autonomic computing
*edition management to run multiple version of the JEE application and interrupt free upgrades
*policy based SLA ensurance to focus on key applications
*maximize middleware infrastructure investment
*rule based routing

2. Explain what is ODR?
"The WebSphere Virtual Enterprise On Demand Router (ODR) component provides capabilities such as workload balancing, prioritization, health monitoring, and dynamic operations for dynamic clusters. An ODR can be configured to provide multi-cluster routing, including dynamic clusters located in remote cells, and routing to other servers that are not running WebSphere Virtual Enterprise. The ODR can serve as a replacement for the HTTP server plug-in, but in many configurations both components are used. The HTTP server could be located in the demilitarized zone to serve static content and to provide an entry point to the private network where the ODR resides." - IBM documentation

Think of ODR as a highly intelligent Web Server or Web Server plugin. It does not only route traffic to application server clusters according to a fixed weighted method such as Round Robin. It has the intelligence to understand the state of the application server and adjusts itself in routing behavior. The correct configuration and timely and wise application or ODR fixes are critical in keeping your WebSphere Virtual Enterprise system stable. ODR is the most critical component of WebSphere Virtual Enterprise.

3. What is a dynamic cluster?
"A dynamic cluster is a server cluster that uses weights and workload
management to balance the workloads of its cluster members dynamically,
based on performance information that is collected from the cluster
members. Dynamic clusters enable application server virtualization. "  - IBM documentation

The key here is load - the dynamic cluster can adjust load based on load between its members.

"A dynamic cluster is an application deployment target that
can expand and contract depending on the workload in your environment.
Dynamic clusters work with autonomic managers, including the
application   placement controller and the dynamic workload manager to
maximize   the use of your computing resources. Dynamic clusters are
required   for many of the WebSphere Virtual Enterprise autonomic
functions, including high availability and service policies." - IBM documentation

The critical message here is dynamically increase or reduce the number of work JVM instances.

"Dynamic clusters are similar to the server clusters that you can
create with WebSphere Application Server Network Deployment , but key
differences exist that make dynamic clusters much more robust. For
complete life-cycle management servers, the product controls the
creation and deletion of server instances and can start and stop servers.
For assisted life-cycle management servers,the product can control the
state of servers by stopping and starting servers from a pool of
predefined server instances. " - IBM documentation

Well - WAS ND cluster is static and WebSphere Virtual Enterprise has dynamically changing clusters if you switch to automatic mode of operation among "Manual, Supervised, and Automatic".

4. Explain what is the current IBM recommended upper limit for core group?
The members of the core group talk to each other by inter-process communication (IPC). "A CoreGroup is a set of WebSphere servers having a Group Communications System (GCS) fabric, which can be used for Virtually Synchronous messaging. WebSphere environment allows mulitcasts among the members of a core group." Therefore, if the size of the core group is too large, hence the communication burden as well as possible performance degradation. The last IBM recommendation that I heard was Keith Smith (the chief architect of WAS XD): 50 or less.

5. Explain what is the inter-process communication mechanism replacing core group (service bulletin board) for WVE 6.1.1?
WVE's Bulletin Board (WVEBB) uses scalable peer-to-peer technology and WVEBB removes all WVE dependencies on HA manager and core groups. This is an important architectural change that tends to make your WVE environment more stable. The Bulletin Board (WVEBB) is disabled by default. For details, please see this WebSphere Virtual Enterprise article.
IBM WVE article

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Come across some JEE job interview questions - may be useful to WAS professionals as well since JEE application server is a subset of JEE specification: JEE Interview Questions

A very good WAS interview question sample with answers: WAS Interview Questions

Another with detailed answers: Questions with detailed answers

Keep the Admin Console Open

2011-03-31T06:04:00.000-07:00

The WAS Admin Console times out in 30 minutes - very inconvenient.

You can use this Jython program to change the time out value or modify the file directly. (this code will not work unless you fix the indention that is meaningful to Jython. I cannot get this blog editor to do indention easily)

# This progam extends the time out value for WAS admin console
__author__="IBM Red Book Authors"
__date__ ="$Jan 28, 2011 8:55:48 AM$"
dep = AdminConfig.getid("/Deployment:isclite/" )
appDep = AdminConfig.list("ApplicationDeployment", dep )
sesMgmt = AdminConfig.list("SessionManager", appDep )
# check if existing sesMgmt there or not, if not then create a new one, if
# exist then modify it
if (sesMgmt == ""):
    # get applicationConfig to create new SessionManager
    appConfig = AdminConfig.list("ApplicationConfig", appDep )
    if (appConfig == ""):
        # create a new one
        appConfig = AdminConfig.create("ApplicationConfig", appDep, [])
        # then create a new SessionManager using new Application Config
        sesMgmt = AdminConfig.create("SessionManager", appConfig, [] )
    else:
        # create new SessionManager using the existing ApplicationConfig
        sesMgmt = AdminConfig.create("SessionManager", appConfig, [] )
        # endElse
# endIf
# get tuningParams config id
tuningParams = AdminConfig.showAttribute(sesMgmt, "tuningParams" )
if (tuningParams == ""):
    # create a new tuningParams
    AdminConfig.create("TuningParams", sesMgmt, [["invalidationTimeout", 1420]])
else:
    # modify the existing one
    AdminConfig.modify(tuningParams, [["invalidationTimeout", 1420]] )
    # endElse
# saving the configuration changes
AdminConfig.save()

WebSphere Job Interview Sample Questions 001

2011-03-30T16:53:00.000-07:00

What is a virtual host?

Virtual hosting is a method for hosting multiple domain names on a computer using a single IP address. You can use admin console environment > virtual host to modify alias and assign port numbers (alias plus port numbers = virtual host)

How do you configure JDBC and JMS resources?

First create a JDBC provider (a JDBC provide encapsulates the JDBC driver for a specific database). From the admin console Resources > JDBC Providers.
Then, create and configure the datasource that is associated with the proper JDBC provider. The datasource is the connection that the Java application uses to connect to the database. Resources > Data Sources are the panels to use in system configuration.
Be particular consistent with the JNDI name of the data source. The JNDI is used in the Java application to access the database
Type 2 driver - you need client - Type 4 driver - pure Java
For Type 4 Driver, you will need

server name
database name
port number
authentication mechanism along with security credentials (for example, username and password, authentication - JAAS)

Connection pool - performance consideration - max and min connection size

Configure MQ JMS provider
Configure Connection Factory and but very careful about the JNDI name because that it what the developers will use (to create sessions and then, consumers or providers) (binding mode with the local MQ queue manager or client mode where a client connection is needed to connect to a remote queue manager)
Then, create queue or topic
Finally, you have to configure the listener port to connect the dots

Click on the picture to see a very clear picture

WebSphere Application Server > Communication > Messaging > Listener Port > New
The most important items are Connection factory JNDI name and Destination JNDI name these form the connection between the MDB, its connection to listen to and the destination for its messages

What are the steps involved in deploying an application?

Make sure that the resources needed by the application are configured correctly such as JDBC, JMS, virtual host, among others
The ear file is readily available on a local or remote server
Use Application Panel of the admin console and choose new and follow the prompts
Recycle the server and perform post installation certification
Use web.xml to determine the context root and home page for testing - the following is the directory to look for the file -

C:\Program Files (x86)\IBM\WebSphere\AppServer\profiles\AppSrv04\installedApps\DOD02Node03Cell\ivtApp.ear\ivt_app.war\WEB-INF

What is session persistence? What mechanisms does Websphere have for session persistence?

Session persistency is option to recover the session data in case the server crashes or the session data is too valuable to lose. There are two ways to configure session persistency - database or memory to memory replication. The memory to memory replication has better performance and the database approach is more reliable. JSESSION ID is the server side artifact supporting session and prefer local session affinity are both good topics.

Have you used wsadmin? What are the different objects available in wsadmin?

AdminControl - deal with MEAN that represent live object
AdminConfi - deal with configuration stored in the configuration repository
AdminApp - update application metadata
AdminTask - used to access a set of task-oriented administrative commands that provide an alternative way to access the configuration commands
Help - print Help.AdminControl() - this gives you a list of the objects. If you want to read text about each area, you can use AdminControl.help()

Troubleshooting – give couple of scenarios where you were involved in troubleshooting

JVM crashes with memory exhaustion - caused by application logging logic failure and unbounded data structure to hold business records to log
Ear files disappeared without obvious cause - WAS Virtual Enterprise anomaly - system automatically reinstalled application under certain circumstance - suspicion autonomic computing error

Monitoring tools – TPV, Introscope – have you used them?

TPV for light weight monitoring and performance tuning
Introscope dives deep into WAS and the application in the JVM

Describe the most complex topology you have worked with

Some basic UNIX commands, flavors of UNIX you have worked on.

Ultrix - coding - socket, pipe, broadcasting, multicast, distributed large scale cashing
Sun Solaris 9
AIX 6
Red Hat LINUX 9
Ubuntu 10

WebSphere eXtreme Scale Installation

2011-03-30T08:46:00.000-07:00

For a while, this blog will switch direction to WebSphere eXtreme Scale 7.1 because I will help with an IBM Red Book effort on this.

Installation of WebSphere eXtreme Scale 7.1 can be standalone or work with WebSphere Application Server 7.1.

After download the software, you have to set HOME_JAVA environment variable. On Windows platform, it is a bit tricky because the WebSphere eXtreme Scale batch files do not like spaces in directory and file names. For example, the following will not work.

set JAVA_HOME=C:\Program Files (x86)\Java\jdk1.6.0_23

When you launch runcat.bat, you will have error messages complaining about 1) you need to define JAVA_HOME, 2) c:\Program is a not an internal or external command

The following will be acceptable to WebSphere eXtreme Scale batch files.

set JAVA_HOME=C:\Java\dks1.6.0_23

Then, after you launch runcat.bat at install_root\ObjectGrid\gettingStarted\, you will see below. Your WebSphere eXtreme Scale system is ready.

WebSphere eXtreme Scale ready to process requests

WebSphere Installation Factory to produce CIP and IIP

2011-03-30T07:10:00.000-07:00

WebSphere Installation Factory is a tool to produce installation packages - customized installation package (CIP) or integrated installation package (IIP) to install WebSphere software products.

The objective of this tool is to reduce complexity and improve productivity of WebSphere product installation.

Centralized Installation Manager (CIM)

2011-03-29T21:29:00.000-07:00

CIM is a tool to allow remote installation of WebSphere Application Server software (release, refresh pack, fix pack, and interim fixes) without logging into each node.

"The CIM does not take the place of Update Installer or Installation Factory for
WebSphere Software. CIM pushes the product binary files or maintenance to the
remote targets and invokes the standard installer or update installer tool to
perform the installation or apply updates on the target systems."

Unlike update installer, CIM is part of WAS 7 Admin Console. It uses update installer by keeping is as part of the installation package and getting it installed on the node to use for product installation.

CIM is new feature with WebSphere Application Server 7.0.

For more details, refer to IBM Centralized Installation Manager (CIM) red paper.

WebSphere Product Updates

2011-03-29T21:26:00.000-07:00

What product updates

Release - a major version for WebSphere, for example, 7.1 (the first two digits)
Refresh pack - an update with both fixes and new functions, for example, 6.0.2 (the third digit)
Fix pack - fixes only, for example, 6.0.1.2 (the fourth digit)
Interim fix - an update to fix a specific problem or a number of specific problems

Product update strategy

Product updates are expensive engineering tasks because the extensive testing required. Therefore, a balanced must be achieved between the need to run a relative updated WebSphere product and resource and production environment stability consideration.

To get on the most recent release may not be the best idea. Any software needs time to mature. The current release minus one might be a sensible approach.

Usually, two scheduled WebSphere product updates a year is adequate. These two may be a major releases, or refresh packs or even fix packs. It depends on many factors such as the WebSphere technology road map of your company as well as need of the JEE applications and the specifics of your enterprise engineering practice.

The technical process

Defining versions and updates as well as technical objectives
Use versionInfo.sh or versionInfo.bat determine the current product version

Version Information Report

Go to IBM WebSphere support site to locate the desired product update
Get the product update desired
Stop the servers and backup the configuration by using backupConfig.sh or backupConfig.bat
Extract the files into the WAS product root
Install update installer from IBM Support Site

Download the proper update installer
Install the update installer - go to product root, for example c:\Program Files (x86)\IBM\WebSphere\UpdateInstaller
Launch install - is:javahome C:\Program Files (x86)\IBM\WebSphere\JDK\jre.pak\repository\package.java.jre\java
Then, install the installer by invoking the install.bat program again

Run the installer
Restart all WAS processes - the servers on this node and Dmgr
Check the systemOut.log to see if the server starts cleanly
Repeat the same for other servers on the cell

Tivoli Performance Viewer

2011-03-28T14:59:00.000-07:00

TPV is a useful tool, especially the charts for web container and JVM, among other. Here are some teaser questions:

What are the PMI monitor levels?

None
Basic
Extended
All
Custom

What is the default setting?

Basic

Where to go for setting the PMI monitor levels?

Use Admin Console - Performance Monitoring Infratructure (PMI) > server_name
Use WSAdmin

Where is the PMI data log file and what is the name of this log file?

Monitoring and Tuning > Peformance Viewer > Current Activity > server_name > Settings > Log
then, you can define_log_file_name or use default that is "tpv.xml"

What you can view by using TPV?

DynaCache
EJBModule
EntityBean
JDBCProvider
J2CResourceAdapter
JVM
MessageDrivenBean
ORB
Server
SessionManager
StatefulSessionBean
StatelessSessionBean
SystemMetrics
ThreadPool
TransactionService
WebModule
Servlet
WLMAppServer
WebServicesService
WSGW

Can you use TPV to view sysem.log file?

No, you cannot. TPV can view TPV performance data in tpv.xml file

When you use TPV and when you use ITCAM or Introscope?

When you need to know which ojbect in JVM is the problom
When you want to track transaction

WebSphere troubleshooting

2011-03-27T16:51:00.000-07:00

Recently I had the good fortunate to meet with a very senior WebSphere system engineer who works for a large financial services company. The discussion focused on WebSphere troubleshooting. Here are the notes that I took from the conversation.

Have an end-to-end view in WebSphere troubleshooting, from browser all the way to the backend system.
First, test JVM to see if it is working. Make sure that the JVM is up and running and there is no hang thread. Turn on verbose GC and look into system log and native_std.log for JVM related error message.
From the browser, to be if the URL is working. If the return code is 500 internal error, this may be a JVM or plugin issue. If the return code is 404 page not found error, it may well be a web server problem.
Try to browse into the transport port of the web server and application server directly. If there URL works, then, you can exclude the web server and application server from the troubleshooting scope.
Use "telnet server_name port_name" to test network connectivity and server status or test other components of the system, for example MQ server with a port number of 1470.
Look into the access log of the web server to see if any request has actually made to the web sever and not got stuck with the 3DNS or BIG IP. Also look into error logs to see if there are any plugin problems and SITEMINDER issues.
If there is high CPU, usually it is bad application code.
If there is high memory consumption, create heap dump with kill -3 helps. You can ship the dump to IBM for analysis if your work station does not have enough memory to run the Support Assistance suite of tools.
Check connection pool - a frequently seen problem is a bug in the JEE code that does not close the connection after using. This causes a connection leak. Use "telnet server_name 446" to examine the network connectivity between the WebSphere Application Server and the backend systems. This will also tell you if the server is actually up and running. Sometimes, the piling up of connections is due to a connectivity issue. Use TPV, Introscope, or ITCAM to inspect the connection pool as well as examine system log for connection timeout.
It helps tremendously if you have transaction monitoring capability. Then, you know exactly where the transaction got stuck or slows down. Introscope provides this capability, though you need in-depth expertise in Introscope that takes time to build.
The capability to monitor user experience and transaction is critical in troubleshooting.

Performance Tuning

2011-03-26T17:28:00.000-07:00

What is performance tuning?
Performance tuning is turn WebSphere an extensive number of "knobs" and parameters that you can use to enhance an application’s performance according to the specific needs of each application.

When to tune?
Do not try to fix anything that is not broken. Only do performance tuning at performance testing or when there is a performance problem identified.

Performance tuning strategy?
Have a holistic view of the WebSphere system from the geographical load balancer all the way to the back

What to tune
What to tune depends on the specific JEE application. The most frequently tunable areas are the following.

JVM, especially for memory bound applications. Ensure that the heap size is large enough but not too large to cause a long pause. There is not fixed "gold rule" for heap size. For example, I have seen heap as large as 2GB that works well. It depends on the application. For application that has many small and short lived objects, you may want to experiment on having a large "nursery". Even though for a 64 bit system, there is theoretically no upper limit but the constraint of available physical memory, too large a heap certainly can cause problems due to the "stop the world" compact cycle of garbage collection.

EJB container - EJB thread is a custom property. You want to use ITCAM or Introscope to detect thread usage and tune accordingly.

Web container for web applications - web container thread is the most common bottleneck, especially for high load systems. You have to watch for creeping increase of load. For a very stable WebSphere system, the stead but slow increase of load over the years may eventually become unstable. When thread saturation occurs, it may manifest itself as a JVM heap problem because of within the JVM, large number of requests are piling up. Increase of vertical clustering has been an effective means that I used over the years to fix this problem. Most of the application code supports vertical clustering, with the exception of the rare situation where the application code uses a unique counter or software router kind of Java artifact. Quite a number of applications have logic that do not support horizontal cluster. For this type of JEE application, vertical clustering is the only means to achieve a level of inter-JVM fail-over and increase of thread processing capability. It is very helpful to work with the application development team not to design and code JEE applications that do not support vertical and horizontal clustering.

JDBC connection pool - a usually problem is the too low a setting for the load, if you see a number of waitForConnection exception and timeouts in the log files. Now it is time to test increased connection pool size.

JMS - the number of connection, the max retry value, and the number of messages in a session are among the tunable parameters.

OS - The ulimit value, the network (MTU), and amount of memory, and the CPU allocation, among others, contribute to the performance of WebSphere Application Server.

Web Server - are you running in worker mode where you can take advantage of web server threads or refork mode where the web server process forks to serve each request? Thread settings, timeout values, and the location of the web server impact the performance of the WebSphere system. Look for warnings about reaching MaxClients. Here is a useful web server tuning guide on WAS 6 .

What are the "knobs" and parameters?

JVM heap size
Thread pool size
Connection pool size
Data source statement cache size
ORB pass by reference
Servlet caching

JVM heap size

The increase of the heap size should be balanced with the time and pause needed for garbage collection.
The high (maximum) and low (minimum) heap settings should be equal to prevent the dynamic heap size adjustments.
Default of 50 and 256 MG is usually inadequate (it is wrong to take these default settings as optimal or IBM recommended settings. For some applications, a relatively small heap may work the best while for others, a very large heap has the best performance. It is purely a matter of performance testing and tuning).
The right heap size tuning can only be achieved via testing (turn verbose garbage collection on when testing).
Using free heap after collection to isolate memory leak.
garbage collection policy is a main GC tuning parameter.

optthruput: (default) mark and sweep during garbage collection when the application is paused to maximize throughput.
optavgpause: mark and sweep while the application is running to minimize pause times to get the best response time.
gencon: manage short-lived and long-lived objects differently to provide a combination of lower pause times and high throughput.

Thread pool size

Minimum size	The minimum number of threads that the contain will keep in the pool. After the number is reached with thread adding into the pool, this minimum pool is kept regarding they are busy are idle.
Maximum size	The maximum number of threads to maintain in the thread pool. To set this too high can cause JVM resource issues and halt the application
Thread inactivity timeout	The amount of inactivity (in milliseconds) that should elapse before a thread is reclaimed. A value of 0 indicates not to wait, and a negative value (less than 0) means to wait forever.

Connection pool size
Making connection and tearing up the connection is resource intensive. A connection pool allows the reuse of a connection to improve performance.

Minimum connections	The minimum number of physical connections. If the size of the connection pool is at or below the minimum connection pool size, an unused timeout thread will not discard physical connections. The pool does not create connections only to maintain the minimum connection pool size.
Maximum connections	The maximum number of physical connections possible for this pool. If this number is reached, no new physical connections are created; requestors must wait until a physical connection returned to the pool, or until a ConnectionWaitTimeoutException is thrown, based on connection timeout. Too high a maximum connections value can stress or even overwhelm the back-end.
Thread inactivity timeout	The amount of inactivity (in milliseconds) before a thread is reclaimed. A value of 0 = no wait, and a negative value = wait forever.

Data source statement cache size
Data source statement cache size is for improve the performance of prepared statement and callable statement. Try to get the number of these statements and make the size equal to that statement. Then, test and increase the size till you see no discarded statement. This is how to adjust this knob.

Data sources > Derby JDBC Driver XA DataSource > WebSphere Application Server data source properties.

ORB pass by reference
This is the same like in C++. Pass by value method creates a new copy of the object. This method is more costly than pass by reference.Using the following panel to change this.

Servers > Server Types > Application servers > server name > Container services > ORB Service

Servlet caching

Use DynaCache to cache fragments for Servlet can improve performance. Servlet caching can be enabled in the administrative console by navigating to Servers => Application servers => server_name => Web container settings => Web container.

Tools
TPV, Introscope, ITCAM all provide help in performance tuning. However, without real time capability to monitor and measure all the way from browser to the backend 1) user experience, 2) transaction, your ability to fully understand what is going in the system is limited.

WebSphere backup and restore

2011-03-24T21:47:00.000-07:00

1) Backup and restore configuration file or profile: please see this link by Sunil Patel.
2) Backup a profile: manageprofiles.sh -backupProfile -argument

Session management tuning

2011-03-24T21:20:00.000-07:00

Session tuning has three objectives to me.

performance (Write frequency， Scheduled invalidation， Tablespace and row size）
Special characterics desired （Session affinity， Write contents， Multirow schema, Session object size, Session cache size, persistent store IO, ）
problem avoidance （session replication, session overflow, session security, session serialization)

Application Binding

2011-03-22T20:25:00.000-07:00

What is application binding?

Application binding could be viewed as a system configuration task. The purpose of the task is to inform WAS where is the physical artifact for a specific name. The mechanism for making this connection is JNDI and some configuration files of an application (ibm-xxx-bnd.xml or ibm-xxx-bnd.xmi).The xml suffix is for WAS 7 and xmi suffix for earlier WAS releases.

What to bind?

EJB
Data Source for EJB
Backend ID for EJB model
MDB
Resources

JDBC
URL
JMS connection factory
Java Mail

Virtual host for web model
Message destination references

When to bind?

Development time
Assembling time
Deployment time
Configuration time

Apache, Plugin, and WebSphere Application Server 7 on LINUX

2011-02-27T21:26:00.000-08:00

Install apache 2.2 on Linux.

sudo apt-get install apache2

Download and install the plugin.

/etc/apache2/apache2.conf includes the /etc/apache2/httpd.conf file.

# Include all the user configurations:
Include httpd.conf

/etc/apache2/httpd.conf file includes the following codes.

LoadModule was_ap22_module /opt/IBM/WebSphere/Plugins/bin/mod_was_ap22_http.so
WebSpherePluginConfig /opt/IBM/WebSphere/Plugins/config/apache01/plugin-cfg.xml

Note that it is was_ap22_mode, not was_ap20_mode. Otherwise, you may have an error complaining about a socket address format.

The .so file is the actually native code module performing the plugin function. The LoadModule directive is to load the native code at the initiation of the plugin proram. The second directive is telling the web server and plugin program where to find the configuration of the plugin program.

For example, when the web server gets a request:

http://DFAPP01.com/hello

The request is sent to the web server. However, as soon as the plugin is installed, according to IBM documentation, the plugin examines all the incoming requests for the web server and forward requests for static contents to the web server and dynamic pages to the app server. The plugin sends right page back the requesting browser.

Two more notes -

Installing IBM HTTP server 7 can encounter Java incompatibility, you may have to run the following, sometimes, without success.
```
java -cp `pwd`/setup.jar -Xms48m -Xmx384m run
```
Also, in Windows, running genPluginCfg.bat may run into a run time exception PLGC0033E that requires you to open an IBM PMR to manage.

"PLGC0033E: A run-time exception occurred while generating the plug-in configuration:
Explanation: A problem resulted from generating the configuration file.
User Response: Examine the exception for nested exceptions and error codes. Rerun the GenPluginCfg script with the -debug option set to yes (GenPluginCfg -debug yes), to see trace details. If the problem persists, see the problem determination on the WebSphere Application Server Support Web page on http://www.ibm.com/software/webservers/appserv/was/support/."

You can test the web server and web server plugin installation and cnfiguration, by using browser to bring up WAS default applications via the web server default transport 80. http://DFAPP01.com:80/hello

Star, stop, and restart and configuration change

sudo /etc/init.d/apache2 stop
sudo /etc/init.d/apache2 start
sudo /etc/init.d/apache2 restart

Recycle the application server after web server plugin changes.

Trace facilities (enabling and selecting components and logging configuration)

2011-02-26T15:20:00.000-08:00

Question 1 - how many log files that one WebSphere Application Server uses?
Question 2 - how many set of trace or error message panels there are on the admin console?
Question 3 - the differences between JVM logs and Process logs?
Question 4 Which logs are the most important or the most frequently used in troubleshooting?

Answer 1 - 7 log files

Diagnostic Trace (trace.log)
JVM Logs (SystemOut.log, SystemErr.log)
Process Logs (native_stdout.log, native_stderr.log)
IBM Service Logs (activity.log - runtime events and can only be viewed by Log Analyzer)
NCSA access and HTTP error logging (http_access.log)

Answer 2 - three set of panels and each set has three panels

Troubleshooting

Logs and trace
Configuration problems
Class loader viewer

Configuration Validation

Configuration error
Configuration warning
Configuration information

Diagnostic Provider

Tests
State Data
Configuration Data

Runtime Messages

Runtime error
Runtime warning
Runtime information

Answer 3 - JVM logs have trace or error messages from the JVM and Process logs contains trace information and error messages from native code (native code is non-Java code, typically found in files with .dll, .exe, and .so extensions).

Answer 4- the JVM log files are the most frequently used in monitoring the server and troubleshooting if not the most important as well.

Here is an IBM Red Paper on tracing and logging - a very good one (some contents, for example, the collector tools are bit old. The current method is us AutoPD, not the collector. However, I am sure many are still using the collector to do MustGather).

Web server has the following logs files as well as the web server plugin.
– Access log: \logs\access.log
– Error log: \logs\error.log

dumpNameSpace

2011-02-26T10:47:00.000-08:00

What kind of typical problems in troubleshooting involves using "dumpNameSpace.sh"?

sudo ./dumpNameSpace.sh -root server -port 2801

Enabling Verbose GC

2011-02-26T10:41:00.000-08:00

Use these panels - Application servers > ClstAppSrv01 > Process definition > Java Virtual Machine, then, check the following

Verbose garbage collection

Of course, you can always use wsadmin

AdminTask.setJVMProperties('[-nodeName D-F-02Node01 -serverName ClstAppSrv01 -verboseModeClass false -verboseModeGarbageCollection true -verboseModeJNI false -runHProf false -hprofArguments -debugMode false -debugArgs" -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=7777" -executableJarFileName -genericJvmArguments -disableJIT false]')

How can I learn WebSphere Application Server 7 Network Edition?

2011-02-25T19:47:00.000-08:00

You can download an evaluation copy of WAS 7 Base. However, IBM does not offer an evaluation download for WAS 7 ND. This poses a problem for those who want to learn WAS 7 ND. How to solve this problem?

My recommendation is to use the free download of IBM WebSphere Application Server Network Deployment 8.0 Beta. WebSphere technologies are mature and stable. Even WAS 8 ND (Beta) release has reached a high level of stability. It has all the WAS 7 ND functions and more. I have found that WAS 8 ND (Beta) very helpful in not only learning how to use WAS 7 ND, but also practicing on the flexibility management features of WAS 8 ND with Job Manager and Administrative Agent.

Here is the download site for WebSphere Application Server 8 ND (Beta) for Windows.

Generate Dumps

2011-02-25T19:38:00.000-08:00

1) Use wsadmin jython code for thread dumps (be careful that indention is meaningful in jython)

------------------------------------------------------------------------------------------------------
# define a function that will find the JVM name and generate the dump
# the name of the jython program is wasgeneratethreaddump.py
def generateThreadDump(serverName):
serverJVM = AdminControl.queryNames("type=JVM,process="+serverName+",*")
AdminControl.invoke(serverJVM,"dumpThreads")
# call the function
generateThreadDump("ClstAppSrv02")
-------------------------------------------------------------------------------------------------------

Use the following in wsadmin to call the jython program (windows):

wsadmin -lang jython -f wasgeneratethreaddump.py

Then, you should see the dump file. You can use IBM Support Assistant to view and analyze the dump.

2) heap dump

A. Use admin console to set up automatic memory dump - this is only for testing and development OR when you have a severe production problem, because the generation of dump will cause the production system an actual pause. Use the following sequence of panels, then, check "Enable Performance and Diagnostic Advisor Framework (Runtime Performance Advisor)"

Application servers > ClstAppSrv01 > Performance and Diagnostic Advisor Configuration

B. Use wsadmin and jython to generate a heap dump

------------------------------------------------------------------------------------------------------
# define a function that will find the JVM name and generate the dump
# the name of the jython program is wasgeneratethreaddump.py
def generateThreadDump(serverName):
serverJVM = AdminControl.queryNames("type=JVM,process="+serverName+",*"
AdminControl.invoke(serverJVM,"generateHeapDump")
# call the function
generateThreadDump("ClstAppSrv02")
-------------------------------------------------------------------------------------------------------

3) Of course, both can be generated from using kill -3 taking JVM PID as argument in UNIX/LINUX environment (be careful - sometimes there are anomalies - once I got into trouble issuing kill -3 because of a bug in a monitoring tool. Generally speaking, wsadmin and jython is a safer route)

java dmp
javacore txt
Snap trc

SOAP/HTTP or SOAP/JMS

2011-02-21T08:31:00.000-08:00

SOAP/HTTP

For external endpoints
Firewall friendly (web services exposed over internet)
Supported on all platforms
Clients can be simple and lightweight
Dynamic caching (to improve performance)

SOAP/JMS

Intranet endpoints
Assured delivery and only once delivery
Publish and subscribe and asynchronous support
Better scalability and reliability
Marginal better performance
Better support in middleware software
Transaction support

WAS 7 and Web Services Standards Support

2011-02-21T05:30:00.000-08:00

Keep the following for quick reference.

WS-I Basic Profile 1.1 - this is about interoperability and WSDL. It provides interoperability guidance for core Web Services specifications such as SOAP, WSDL, and UDDI. The profile uses Web Services Description Language (WSDL) to enable the description of services as sets of endpoints operating on messages.

JAX-WS - The Java API for XML Web Services (JAX-WS) is a Java programming language API for creating web services.

Java API for XML-based RPC (JAX-RPC) allows a Java application to invoke a Java-based Web Service with a known description while still being consistent with its WSDL description. It can be seen as Java RMIs over Web services. JAX-RPC 2.0 was renamed JAX-WS 2.0 (Java API for XML Web Services). JAX-RPC 1 is deprecated with Java EE 6.^[1]

UDDI V3 - Universal Description, Discovery and Integration is a platform-independent, Extensible Markup Language (XML)-based registry for businesses worldwide to list themselves on the Internet and a mechanism to register and locate web service applications.

WS-I Security - WS-Security (Web Services Security, short WSS) is a flexible and feature-rich extension to SOAP to apply security to web services. It is a member of the WS-* family of web service specifications and was published by OASIS.

WS-Transaction - WS-Transaction - a Web Services specification developed by BEA Systems, IBM, and Microsoft. The WS-Transaction specification describes coordination types that are used with the extensible coordination framework described in the WS-Coordination specification. It defines two coordination types: Atomic Transaction (AT) for individual operations, and Business Activity (BA) for long running transactions.

WebSphere Concepts - Groups and Clusters

2011-02-21T04:35:00.000-08:00

It is sometimes confusing about all the WebSphere groups - node group, default group, core group, cluster, and dymanic cluster. Here is a quick summary.

node group - a group of nodes of similarity within one cell. For example, a cell can have a two node groups of zOS and one node group of nodes on distributed platform. To me, the node group provides logical grouping of application servers and made system administration easier.

default group - usually, on WAS ND, if you do not specify node groups, all in one cell belongs to a defaultnodegroup.

cluster - A cluster is a collection of servers managed together. Clusters behave as a single application server entity to accomplish a job by parallel processing. The intent of clustering is high availability and failover. A frequently ignored important aspect of clustering is that it can be effectively used to increase system resources to a set of applications in order to improve throughput and overall JVM level capacity.

all cluster member must be within the same cell
all cluster member must be in the same node group
a cluster member can only belong to one cluster
a cell can have one ore more clusters
all members must run the same set of applications

core group - a group of clusters in a high availablity envrinment. All of the application servers of a cluster included in a core group are automatically members of that core group. Core groups enables Websphere Application Server to provide high availability for applications You can also configure core groups to communicate with each other using the core group bridge. The core groups can communicate within the same cell or across cells. Core group works with high availability manager and communication bridges. The intent of core group is high availability.

dynamic cluster - A dynamic cluster is a concept and mechanism used by WebSphere XD to manage a dynamic WebSphere environment. It monitors performance and load information and is able to dynamically create and remove cluster members based on the workload. The intent of dynamic cluster is dynamic provisioning of JVM as well as application edition management.

IBM Cloudburst, IBM WebSphere Cloudburst Appliances, and IBM WebSphere Application Server 7 Hypervisor Edition

2011-02-19T19:35:00.000-08:00

The IBM Cloudburst is a fairly large server - looks like a highend mid-range server. If you do not want to run hypervisor on "general purpose" hardware, the IBM Cluadburst is where you want to go.

The IBM WebSphere Cloudburst Appliance is a thin box that looks like a DataPower appliance. It has WebSphere Applications server images and WAS topology patterns as well as system management tools. You can deploy these to IBM Cloudburst or virtualization ready servers (servers running hypervisor).

IBM WebSphere Application Server 7 Hypervisor Edition is the Websphere server that can be deployed and execute in a cloud.

A metaphor - what is a "bare metal" hypervisor?

2011-02-19T18:01:00.000-08:00

To call "bare metal" hypervisor a hypervisor is not as good as calling it "hardware simulator", because to the guest operating systems, the "bare metal" hypervisor is simulated hardware.

WebSphere CloudBurst Appliance

2011-02-19T17:33:00.000-08:00

Cost in IT acquisition and operation costs are cited in WebSphere CloudBurst Appliance advantages. Lowering costs are extremely important.

However, the most compelling motivation to use WebSphere CloudBurst Appliance may very well be reduced time to market. To design, build, configure, and test WebSphere infrastructure is a time consuming process, not to say that you have to take into consideration that acquisition of servers take time, especially for large corporations.

Anything that can help a project team to reduce the time to get on a working middleware infrastructure help way beyond reducing costs only. This is perhaps the greatest value of WebSphere CloudBurst Appliance.

In the world of large new WebSphere technology deployment, we need both "Agile in a Bird Case" and "Anarchy Led Engineering Discipline".

2011-02-19T06:38:00.000-08:00

In the world of large scale new WebSphere deployment (development and engineerning), I think that we need to both loosing down and tightening up with new approaches.

In the area of development, the goal of working software has to take priority with Agile methodology leading the way. However, a compromise is needed in a very large and heavily regulated environment where documentation and approval process must be provided due to legal and privacy concerns. All the following Agile objectives remain true, while new adaptive approach can help.

Individuals and interactions over processes and tools
Working software over comprehensive documentation
Customer collaboration over contract negotiation
Responding to change over following a plan

However, the complete lack of long-planning is not possible for any modern IT projects, even we fully appreciate and adopt Agile Methodology. Maybe a "bird case" approach is in the Agile based projects, especially those taking on totally new technology and unchartered territories. An overall long-term project is in place that cut into manageable pieces - "bird cases" within which the bird - Agile based development fly freely. Hopefully, this will achieve the need for control large projects and taking the full advantage of Agile and Scrum methodology.

On the other hand, the infrastructure engineering must follow tighter design procedures, change process, operation manuals, and engineering standards. This is because the malfunction of infrastructure causes potentially heavy loss and disruption as well as the nature of infrastructure - it is time consuming and costly to fix some of the infrastructure issues, for example, change the design of your middleware in the middle of its production operations. At the same, a gradual, POC based approach works better for new technology adoption that will help with the following. The introduction of new technology demands a level of anarchy and a degree of chaos for the team to figure out what to do. However, this intended anarchy and purposeful chaos must lead to the following.

Building the team's technical skills over the new technology
Creating and documenting engineering processes - the foundation of engineering process optimization and automation
Nurturing internal and external working relationships that are critical in designing, building, and operating the new infrastructure
And the most importantly, delivering a gradually maturing IT infrastructure in support of the business drivers

Therefore, we have to seriously consider Agile and Scrum in large new WebSphere technology development and deployment while making substantial adjustment to achieve success for providing a new IT paradigm of innovation for new business imperatives and objectives.

Job Manager is a bless

2011-02-17T18:26:00.000-08:00

What is Job Manager? In a simplistic way, it is your centralized WebSphere "crontab". For example, you can schedule a weekly recycling of many clusters and servers. Then, the job manager will get the job done and send you an email. What a bless for system engineer!

Add nodes to an administrative agent

2011-02-17T16:42:00.000-08:00

To add nodes to an administrative agent, you have to use \AppServer\bin\registerNode command. The following is an exmaple. Note: this is NOT a wsadmin command!

set WAS_HOME=C:\program files (x86)\IBM\WebSphere\AppServer

set adminAgentProfileName=AdminAgent01
set adminAgentHostName=localhost
set adminAgentSoapPort=8877
set baseProfileName=AppSrv05

cd %WAS_HOME%\profiles\%adminAgentProfileName%\bin
registerNode.bat -profileName %adminAgentProfileName% -profilePath "%WAS_HOME%\profiles\%baseProfileName%" -host %adminAgentHostName% -conntype SOAP -port %adminAgentSoapPort%

Look for port numbers?

2011-02-17T16:11:00.000-08:00

Look for port numbers for a JVM? Go to the config directory and look for serverindex.xml.
For example, if you look for the admin console port for an administrative agent, go to the below sub-directory.

\profiles\AdminAgent01\config\cells\DF-02AACell01\nodes\DF-02AANode01\serverindex.xml

Then, you find the port number, for example, the port to access admin console. Now it is possbile to access the admin console. Let me if you have a better way such as using wsadmin.

Messaging - What is Message Driven Bean?

2011-02-09T04:10:00.000-08:00

What exactly is Message Driven Bean (MDB)

From the perspective of Java artefact, it is an EJB specified by EJB 2.1. It is a stateless session bean.
It is a consumer in terms of the messaging programming model.
It implements javax.ejb.MessageDrivenBean (container life-cycle management).
It implements javax.jms.MessageListener interface.
It implements ejbCreate() method.
The EJB container maintains a pool of method-ready MDB.
When a message comes, the container selects a MDB from the pool to process the message.
The container removes an MDB by invoking ejbRemove() method.
The transaction can be container managed or bean managed.
To associate an MDB with destination on SIB, use JMS activation specification.
To associate an MDB with a destination on MQ, use listener port.