[jboss-dev-forums] [Design of Messaging on JBoss (Messaging/JBoss)] - Re: Server side HA and failover

[bstansberry@jboss.com]

I had a look at the DRM code and was able to refactor it into an abstract version that can easily be subclassed with a version meant to integrate with your ClusteredPostOffice.

So there are some useful classes from the AS for use on the server side.  I created some UML for this, but the free version of the plugin wouldn't export an image :(

1) (impl of) DRM.  DRM basically maintains a distributed version of a Map<String key, Map<String nodeId, Object replicant>>, plus registration/notification of listeners when the data in the map changes. The replicant in the map is whatever you need; in the Remoting case it would be an InvokerLocator.  DRM also calculates a hash of the replicants associated with a key; this hash is meant to be passed back and forth between the client and server; an out-of-date hash from the client tells the server it needs to send an updated cluster topology.

2) An HATarget instance listens to the DRM for changes to a given key and exposes the current hash and list of replicants.

3) ReplicantsManagerInterceptor is a server-side AOP interceptor that compares the hash sent by the client to the one held by the HATarget. If mismatch, get the current replicant list from target and packages it with the response.

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