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We're prototyping a jgroups-based cluster node messaging system that will replace one that was JDBC-based. There are a lot of folks in my organization who are concerned about adding more multicast traffic to an already busy network, so I'm getting some pushback on a UDP/multicast solution.

I know JGroups can be configured to be TCP only, but I do not want to have to force a configuration step into the application where each node has to be identified ahead of time in a config file.

What I'd like then is to see if we can get a hybrid working here where multicast is used ONLY for group membership operations (discovery, heartbeats, failure detection), but messaging is all TCP-based.

I'm not finding examples of that in my searches, however, and am therefore questioning whether JGroups can be configured this way.

Can it, and any example configs showing how?

Thanks!

Scott
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1 Answers1

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As for discovery, using MPING you can do that - it uses IP multicast to discover new nodes, although these later respond via the main transport (TCP in your case).

As for FD/FD_ALL, I don't think it's possible, the protocols are designed to use the main transport. You'd have to write your own FD protocol, shouldn't be that complicated.

However, if you can use UDP, you probably should. It's up to you whether you send a message to one node, multiple ones or all of them - for one destination there will be unicast UDP, for few destinations (if you set the anycast option) will be multiple unicasts used and only for all nodes the UDP will reduce the network load by multicasting. It's really up to the application, UDP just allows multicasts.

Radim Vansa
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