Load Balancing & Clustering
TERACOTTA
Load Balancing & Clustering
Author: Pawan Modi
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TABLE OF CONTENTS
INTRODUCTION ______3
INSTALL TERRACOTTA SERVER ______4
INSTALL GERONIMO SERVER ______5
INSTALL TERRACOTTA CLIENT ______6
UPDATE TERRACOTTA CONFIGURATION FILE ______7 Excerpt from tc-config.xml ______7
START TERRACOTTA SERVER ______8
START TERRACOTTA CLIENT AND GERONIMO SERVER ______9 Starting Geronimo ______9
INSTALL WEB APPLICATION ON EACH GERONIMO CLUSTER MEMBER ______10
SETUP LOAD BALANCING AND FAILOVER ______11 Apache HTTP Server: ______11
MOD_JK SETUP: ______13
TESTING DEMO LOAD BALANCING: ______15
USEFUL LINKS: ______16
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Introduction
Terracotta is open source infrastructure software that makes it inexpensive and easy to scale a Java application to as many computers as needed, without the usual custom application code and databases used to share data in a cluster.
Terracotta manages mission critical data using Network-Attached Memory (NAM) technology. NAM enables Terracotta to cluster Java Virtual Machines (JVMs) directly underneath applications, and is a proven runtime approach to providing Java applications both high availability and scalability.
Terracotta's open source community of developers is sponsored by Terracotta, Inc.
This article describes the steps to cluster a simple web application's HttpSession data using Open Terracotta. The required step includes.
• Install Terracotta Server • Install Geronimo Server • Install Terracotta Client • Update Terracotta configuration file • Start Terracotta Server • Start Terracotta Client and Geronimo Server • Install Web Application on each Geronimo cluster member • Setup Load Balancing and Failover • Testing Load Balancing and Failover • Use the Terracotta admin console
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Install Terracotta Server
Terracotta needs to be installed on one machine that will serve as the Terracotta Server. The Terracotta server will be responsible for maintaining session state and assuring that it is accurately reflected in each of the Geronimo cluster members.
Download the Terracotta Sessions bundle and run the Installer. This example requires "Open Terracotta 2.2.1 Stable 2" or higher.
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Install Geronimo Server
The Geronimo Application Server needs to be installed on each machine that is to be clustered. The example in this article will install Geronimo on two separate machines (cluster members).
Download the Geronimo image that includes the Tomcat web container from the Geronimo
Website and unpack it on each of the cluster members. This example requires Geronimo 1.1.1 with the Tomcat web container. The Jetty web container is not yet supported by Terracotta. Note: - Download only J2EE certified release. Don’t download minimal / little-G releases. Minimal / little-G release doesn’t support administration console. User need Admin console for variety of purposes like new applications deployment etc. Note that the same version release of Geronimo must be installed on each machine to be clustered. Mixing versions of Geronimo is not currently supported by Terracotta.
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Install Terracotta Client
The Terracotta client needs to be installed on each machine that contains a Geronimo cluster member. Currently, the same install bundle includes both the Terracotta server and client. So, it is possible to run the Terracotta Server and Terracotta Client on the same machine with a common installation.
Download the Terracotta Sessions bundle and run the Installer on each cluster member. This example requires "Open Terracotta 2.2.1 Stable 2" or higher.
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Update Terracotta configuration file
The tc-config.xml file identifies which context-roots are to be clustered as well as the data types that are to be placed in the HttpSession. This example will use the Terracotta configuration file that is delivered with the Terracotta distribution. The specific file is: C:\Terracotta\terracotta-2.2.1\sessions\sandbox\tomcat5.5\tc-config.xml
Change the tc-config.xml file to look similar to the following example. Note that the tc- config.xml example below only shows the xml items that are to be updated. Other portions of that xml file should remain unchanged. Remember to change the IP address in the example below to the address of the Terracotta Server.
Excerpt from tc-config.xml
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Start Terracotta Server
Start the Terracotta server specifying the location of the tc-config.xml file that you just updated. cd C:\Terracotta\terracotta-2.2.1\sessions\bin start-tc-server.bat -f c:\Terracotta\terracotta-2.2.1\sessions\sandbox\tomcat5.5\tc- config.xml
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Start Terracotta Client and Geronimo Server
Open Terracotta supports a variety of JVMs and each one requires a unique boot jar be present in the bootclasspath when launching the Geronimo server. The example below is using the Windows JVM that is present in the Terracotta Sessions Package. It is possible to use other JVMs, though a different boot jar will likely need to be created. Also some of the launch arguments in the script below were obtained by issuing the dso-env script in c:\Terracotta\terracotta-2.2.1\sessions\bin\ directory. You should issue this command on your system to find the arguments that are appropriate for your environment.
The IPAddress in the example below needs to be replaced with the IP Address (or hostname) of your Terracotta server. This value will be used to determine which Terracotta server will provide the Terracotta client with its tc-config.xml file. Alternately, - Dtc.config="IPAddress:9510" can be omitted though you will need to update tc-config.xml on each cluster member (e.g. c:\Terracotta\terracotta-
2.2.1\sessions\sandbox\tomcat5.5\tc-config.xml). Review the Terracotta documentation for more details. Here is an example startup on a Windows Machine:
Starting Geronimo
c:\Terracotta\terracotta-2.2.1\jre\bin\java.exe -Xbootclasspath/p:"C:\Terracotta\terracotta-2.2.1\common\lib\dso-boot\dso-boot- hotspot_win32_150_09.jar" -Dtc.install-root="C:\Terracotta\terracotta-2.2.1" -Dtc.config="IPAddress:9510" -jar c:\geronimo-1.1.1-TERRACOTTA\geronimo-1.1.1\bin\server.jar
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Install Web Application on each Geronimo cluster member
Use the Geronimo admin console to install the appropriate example application to each of the Geronimo installations.
Here are links to the example applications and the deployment plan.
servlets-examples-cluster-node1.war - Web application for Cluster Member 1 servlets-examples-cluster-node2.war - Web application for Cluster Member 2 servlets-examples-geronimo-plan.xml - Geronimo common deployment plan (for both cluster members)
Note that the two applications above are identical except for the field which indicates the Server name (e.g. Server1, Server2). This distinction will be useful when testing.
The Geronimo admin console can be accessed at http://localhost:8080/console on each machine. The default id and password for the Geronimo admin console is id=system password=manager. Select "Applications-> Deploy New" from the GUI and follow the instructions on the panel for installing the example application
Now test that the applications were deployed correctly by accessing the applications with your favourite Web Browser:
http://YourHost1:8080/servlets-examples-terracotta/servlet/SessionExample http://YourHost2:8080/servlets-examples-terracotta/servlet/SessionExample
If this is working correctly, it is now time to setup the Load Balancer.
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Setup Load Balancing and Failover
Now you are ready to setup the Load Balancer. We recommend using Apache HTTP server and mod_jk for this example.
Apache HTTP Server:
Install Apache HTTP server - instructions and downloads available at http://httpd.apache.org/ Set environment variable Apache_Home i.e. home directory of Apache http server installation.
Run the Apache .msi file you downloaded above. This will prompt you for: Whether or not you want to run Apache for all users (installing Apache as a Service), or if you want it installed to run in a console window when you choose the Start Apache shortcut. It is recommended to install Apache HTTP server as service. HTTP server start automatically with system boot. User can start / stop / restart Apache HTTP server from \control panel\Administrative tool\services\Apache. Your Server name, Domain name and administrative email account. The directory to install Apache into. (the default is C:\Program Files\Apache Group\Apache although you can change this to any other directory you wish) The installation type. The "Complete" option installs everything, including the source code if you downloaded the -src.msi package. Choose the "Custom" install if you choose not to install the documentation, or the source code from that package.
Test Apache HTTP server is running or not using following link http://127.0.0.1 If Apache HTTP server page is not opening the restart HTTP server from \control panel\Administrative tool\services\Apache & retest above link.
Useful dos commands to control HTTP server To test the Apache configuration files
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apache –t Start Apache using particular configuration file: apache -f "c:\my server\conf\my.conf" apache -f test\test.conf Note: This conf file is httpd.conf
Command to start & stop Apache as service NET START APACHE NET STOP APACHE
To restart Apache from console. apache -k restart
To stop Apache. apache -k shutdown
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Mod_JK Setup:
Download mod_jk binary release from this link http://tomcat.apache.org/download-connectors.cgi
After downloading it is time to configure mod_jk. Steps are as follow Set environment variable CATALINA_HOME i.e. home directory of Geronimo / tomcat server. Rename file mod_jk-apache-2.x.xx.so to mod_jk.so, and place under directory
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Save “workers.properties” file at Apache_Home\conf directory.
Edit file Apache_Home\conf\httpd.conf
LoadModule jk_module modules/mod_jk.so
AddModule mod_jk.c
JkMount /servlets-examples-terracotta loadbalancer
JkMount /servlets-examples-terracotta/* loadbalancer
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Testing Demo Load Balancing:
1] Start Terracotta server using command above. 2] Start HTTP server using command above. 3] Start Geronimo-Tomcat server using command above. 4] Start application “SessionExample” using following link http://YourHost/servlets-examples-terracotta/servlet/SessionExample
Note that the output page contains the ID of the server that is servicing the request. In your browser window, fill in the appropriate input fields and hit the submit button. Add a few more items to your shopping cart. Notice that the browser indicates which server (Server1 or Server2) is servicing your request. Without Sticky Session support, you may see the load balancer alternately route the requests between the two cluster members. If you have setup everything correctly, then the shopping cart data should be present in the session after the browser request moves between the two servers. For Sticky Session, you can test failover by stopping the Geronimo server that is currently servicing the session and seeing that the next http request will failover into the remaining cluster member. The httpsession data from the previous request should be recovered and displayed in the refreshed browser window.
Note: When testing using a web browser, make sure that you erase cookies and cached pages between test cases. Browser caching can cause confusion when testing.
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Useful Links: http://mule.mulesource.org/display/MULE/Clustering http://mule.mulesource.org/display/MULE/External+Clustering+for+Mule http://cwiki.apache.org/GMOxDEV/clustering-geronimo-with-open-terracotta.html http://www.johnturner.com/howto/winxp-howto.html http://www.devside.net/guides/windows/tomcat http://www.cnr.berkeley.edu/~salazar/apache_tomcat.html http://www.debianhelp.co.uk/apachetomcat.htm http://www.devside.net/guides/windows/mod-jk http://tomcat.apache.org/tomcat-3.3-doc/mod_jk-howto.html
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