Configuring load balancing between Apache HTTP Server and Tomcat/tc Server using mod_proxy

Products

• VMware
• Support Only for Apache HTTP
• Support Only for Apache Tomcat

Issue/Introduction

This article provides information on configuring the Apache HTTP Server and Tomcat/tc Server using mod_proxy load balancing. It also provides information on using sticky sessions to send all requests associated with a particular session to the same Tomcat/tc Server worker.

Environment

Apache Tomcat 5.5
Apache HTTP Server 2.0

Resolution

To set up mod_proxy load balancing with Apache HTTP Server and Tomcat/tc Server, the Apache httpd and Tomcat tc Server configuration must be modified. The HTTP(S), AJP, and FTP protocols can be used with mod_proxy load balancing. To use HTTP(S), AJP, and FTP protocols with mod_proxy load balancing, you need these Apache httpd load modules:

• mod_proxy
• mod_proxy_balancer
• One or more mod_proxy_http,
• mod_proxy_ajp
• mod_proxy_ftp

To configure load balancing between Apache HTTP and Tomcat/tc Server using mod_proxy:

1. In the Apache httpd conf/httpd.conf or conf/httpsd.conf, load and configure the mod_proxy modules. A sample configuration appears similar to:
   
   LoadModule proxy_module "/home/ers403/apache2.2/modules/standard/mod_proxy.so"
   LoadModule proxy_http_module "/home/ers403/apache2.2/modules/standard/mod_proxy_http.so"
   LoadModule proxy_balancer_module "/home/ers403/apache2.2/modules/standard/mod_proxy_balancer.so"
   <IfModule mod_proxy_balancer.c>
   ProxyPass /TCSession balancer://mycluster/TCSession stickysession=JSESSIONID|jsessionid
   <Proxy balancer://mycluster>
   BalancerMember http://localhost:8280 route=tcruntime8280
   BalancerMember http://localhost:8380 route=tcruntime8380
   </Proxy>
   </IfModule>
   
   
2. In the Tomcat/tc Server instance(s) server.xml file, ensure that an HTTP connector is created with the port matching the value entered for the BalancerMembers. For sticky sessions, also ensure that a jvmRoute matching the worker name used in the workers.properties file is set. For example, for the two BalanceMembers shown in the preceding sample configuration file, you see:
   
   tcruntime8280 worker:
   
   <Engine defaultHost="localhost" name="Catalina" jvmRoute="tcruntime8280">
   [...]
   </Engine>
   <Connector port="8280" protocol="org.apache.coyote.http11.Http11Protocol" ... />
   
   tcruntime8380 worker"
   
   <Engine defaultHost="localhost" name="Catalina" jvmRoute="tcruntime8380">
   [...]
   </Engine>
   <Connector port="8380" protocol="org.apache.coyote.http11.Http11Protocol" ... />
   

To verify if the configuration is set correctly and the sticky sessions are working:

1. Extract the sample Web application, TCSession.war, from the 2010450_TCSession.zip file attached to this article.
2. Save TCSession.war to each Tomcat/tc Server instance's webapps directory, so that it is deployed.
3. Access the Web application via Apache HTTP server with a UR, such as http://localhost/TCSession.
4. During the first access of a session, you should see a display similar to:
   
   TOMCAT localhost: This is the session id 5B5CF832B4CB62BEEECDABC334043286.tcruntime8380
   This is a new session !
   
   
5. During subsequent requests sent for the same session, you should see a display similar to:
   
   TOMCAT localhost: This is the session id 5B5CF832B4CB62BEEECDABC334043286.tcruntime8380
   This is an existing session
   Session Value: This is in my session

Additional Information

For more information, see:

• http://httpd.apache.org/docs/2.2/mod/mod_proxy_balancer.html
• http://tomcat.apache.org/tomcat-6.0-doc/config/index.html
• http://tomcat.apache.org/tomcat-7.0-doc/config/index.html

Note: The preceding links were correct as of March 13, 2012. If you find a link is broken, provide feedback and a VMware employee will update the link.

• If you see the 404 Not Found error for the Apache httpd load balancer, ensure that the mod_proxy_balancer load module is being loaded into the Apache httpd configuration.
• If you see the 503 Service Unavailable error for the Apache httpd load balancer:
  
• • Ensure that the hostname/IP address and port are correct for the Tomcat/tc Server instances.
  • Ensure that the Tomcat/tc Server instances are up, running, and listening.
  • Ensure that there is no firewall blocking access to the host/port.
    
    
• If load balancing appears to be working, but sticky sessions are not honored, ensure that the name provided in the Tomcat/tc Server configuration for the jvmRoute matches the name that is set for the route property of the BalanceMember in the Apache httpd configuration.

Pivotal Links

Pivotal tc Server Knowledge Base:

https://support.pivotal.io/hc/en-us/categories/200072668

Configuring load balancing between Apache HTTP Server and Tomcat/tc Server using mod_jk