[jboss-dev-forums] [Design of Clustering on JBoss (Clusters/JBoss)] - JBoss server mcast socket bound to network interface

[akostadinov]

Hallo, 

We currently have an issue with running JBoss AS 5 test suite on RHEL 4U5 and above with one node bound to localhost. Please see http://www.jboss.com/index.html?module=bb&op=viewtopic&t=123056 for full details.

Generally On RHEL 4U5 and above when a multicast listener binds to a network interface and a sender is bound to the same interface, the listener can't see any messages unless the multicast route goes through the same interface. (that is not the case with RHEL 4U4 where listener sees messages)

I think because of that if a server is bound to localhost, it can't see mcast messages sent by himself. Thus AS 5 is starting very slowly.

So what I suggest is setting IP_MULTICAST_LOOP on the jgroups mcast socket so it hopefully fix that issue. 
As well not bind the mcast socket to the interface where server was specified to bind with the "-b" option. That way listener will see mcast messages no matter what multicast route the host has.

That is a better behavior besides that it makes test suite runs much more convenient and less error prone. When for example a network admin reroutes the network he will expect that the running AS server will not stop sending/receiving multicast messages properly without needing to add special parameters. 
As well I  don't see any disadvantages in not specifying network interface to bind to. And if there are rare cases with such, the user can specify a startup option to fix that. And behavior will not be much different compared with that on RHEL 4U4 and below.

Please let me know what do you think about that.



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