20.3.2. External load balancer architecture

New in JBoss Enterprise Application Platform 5 are a set of "TransactionSticky" load balance policies. These extend the standard policies above to add behavior such that all invocations that occur within the scope of a transaction are routed to the same node (if that node still exists). These are based on the legacy detached invoker architecture, so they are not available for AOP-based services like EJB3.
  • Transaction-Sticky Round-Robin: Transaction-sticky variant of Round-Robin. Implemented by org.jboss.ha.framework.interfaces.TransactionStickyRoundRobin.
  • Transaction-Sticky Random-Robin: Transaction-sticky variant of Random-Robin. Implemented by org.jboss.ha.framework.interfaces.TransactionStickyRandomRobin.
  • Transaction-Sticky First Available: Transaction-sticky variant of First Available. Implemented by org.jboss.ha.framework.interfaces.TransactionStickyFirstAvailable.
  • Transaction-Sticky First Available Identical All Proxies: Transaction-sticky variant of First Available Identical All Proxies. Implemented by org.jboss.ha.framework.interfaces.TransactionStickyFirstAvailableIdenticalAllProxies.
Each of the above is an implementation of a simple interface; users are free to write their own implementations if they need some special behavior. In later sections we will see how to configure the load balance policies used by different services.