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17.3.2. 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'll see how to configure the load balance policies used by different services.