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From WSO2 ELB 2.0.1 onwards, Pass-Through transport is used, which has introduced significant performance efficiency. The pass-through transport supports extremely high-speed message relaying at the transport level. It uses the high-performing HTTPCore-NIO library and Java NIO concepts to achieve a high throughput specially in direct streaming scenarios.
Apache Axis2 Clustering
Apache Axis2 Clustering module handles membership discovery/management and service membership. There are multiple membership handlers, one for each clustering domain, responsible for managing membership. The "ServiceDynamicLoadBalanceEndpoint" obtains the relevant members of the cluster from the Axis2 membership handlers, and then applys the load balance algorithm to determine the next member to which the request has to be sent.
The Axis2 clustering implementation uses the underlying Apache Tribes Group Management Framework for group membership management.