Chris Shuster 4/29/2009 1Chris Shuster

 Application Servers ◦ Backend processing platform. ◦ Multiple platforms, operating system and architecture. ◦ Multiple programming languages, Java, C++, etc. 4/29/2009 2Chris Shuster

◦ Two primary service architectures for clustering.  Client Side Interceptor Architecture  EJB, JNDI, RMI  Server Side Load Balancing Architecture  HTTP Requests (Servlets, JSP)  Clustering ◦ Presents a unique challenge as compared to static or simple web content. ◦ Handle large volumes of requests. ◦ Necessary to for high availability. 4/29/2009 3Chris Shuster

 Java based application servers only. ◦ JBoss 5 specifically was used.  Server side load balancing architecture was evaluated only.  Apache 2.2.x used as the director. ◦ Utilized the module mod_jk. 4/29/2009 4Chris Shuster

 JBoss nodes are partitioned into clusters.  Cluster partitions can be manually or automatically created. 4/29/2009 5Chris Shuster

Client Side Interceptor Architecture Server Side Load Balancing Architecture 4/29/2009 6Chris Shuster

 Director ◦ Apache  Loaded with mod_jk to forward requests to the application servers. ◦ mod_jk  Similar to mod_proxy.  Supports load balancing algorithms such as weight round robin. 4/29/2009 7Chris Shuster

 JBoss Cluster Nodes ◦ Configuration identical for all nodes.  Cluster membership.  Aware that requests are forwarded.  Session replication for automatic failover. ◦ Configuration unique for each node.  Node name. ◦ Each node has an identical copy of the application, usually in the form of a WAR. 4/29/2009 8Chris Shuster

 Pros ◦ Automatic failure detection and handling. ◦ Automatic session replication. ◦ Automatic distribution of the application to all nodes.  Cons ◦ Single point of failure. ◦ Requires addition software beyond just JBoss. 4/29/2009 9Chris Shuster

 Mitigation ◦ Utilize multiple directors (load balancers).  Cluster and/or failover the directors using LVS or other conventional techniques.  Additional work is required to support session replication among directors. 4/29/2009 Chris Shuster10

 Other methods of providing load balancing. ◦ Apache with mod_proxy. ◦ Hardware load balancers.  Client side interceptor architecture.  Director clustering methodologies. 4/29/ Chris Shuster

 Apache Tomcat Connector ◦ Web Server How To  doc/webserver_howto/apache.html doc/webserver_howto/apache.html ◦ Reference Guide   JBoss ◦ JBoss AS 5 - Clustering Guide ◦ JBoss AS 5 - Installation And Getting Started Guide ◦ JBoss Run Parameters  ◦ Using Mod_jk 1.2 With JBoss  4/29/2009 Chris Shuster12