Wednesday, 19 October 2011
The latest beta of the 5.1 'Brahma' series, 5.1.0.BETA2, is out now and thanks to Dan Berindei, it comes with support for asymmetric clusters which has been highly demanded.
Before asymmetric clusters were supported, it was required that all Infinispan caches that client code interacted against were defined and running in all nodes in the cluster, otherwise, cluster wide messages for a cache that did not exist in a node would fail. So, imagine this scenario where c1 and c2 are user defined caches configured with replication:
Node A [c1] Node B [c1, c2]
Without asymmetric clusters, whenever c2 cache was modified in Node B, a replication message would be sent to Node A, but the replication would fail indicating that c2 was not defined in Node A. This failure would get propagated back to Node B which would result in the modification failing. This kind of problems can particularly affect managed environments such as the JBoss Application Server, because often, deployments will be made in a subset of the cluster, so it could well happen that not all nodes have a particular cache started.
So, what Infinispan 5.1.0.BETA2 'Brahma' brings is support for this type of scenarios by maintaining a view correlating nodes and started caches, hence allowing any node to know which other nodes have a particular cache started. This means that in the above case, Node B would not have sent a replication message to Node A because it would know that c2 was only started in Node B.
The lack of support for asymmetric clusters is what forced Infinispan servers to only accept invocations for predefined caches because these predefined could be started when the servers were started, hence avoiding the asymmetric cluster problem. Now that asymmetric clusters are supported, it’s likely that this limitation go away, but the timeline is to be defined yet.
Tags: asymmetric clusters