[jbosscache-dev] Anycast: JBCACHE-813 & JGRP-338

Bela/Vladimir: Regarding broadcasting calls to a subset of members in a cluster, if I were to callRemoteMethods() to N members ( where N > 1 and N < all members) how does this behave, especially when using TCP or TCP_NIO? I know that with UDP, a multicast is made and the members not on the target list ignore the messages. Is this the same with TCP/TCP_NIO, i.e., is the message broadcast to all members again and the members not on the target list ignore the messages? (Hugely wasteful, and hence the need for anycast). In JBoss Cache 1.4.1, I've implemented JBCACHE-813 so a unicast is used if the recipient list is 1 - a bit of a hack to work around this inefficiency. But this in itself is not foolproof since, say using Buddy Replication in a cluster of 30 servers and using 3 buddies per node, we still end up unicasting the message to all 30 nodes only for 27 of them to ignore it. We could hack in a config param - a unicast threshold (UT) - where if N <= UT and N <= all members, we use a series of forced unicasts? The drawback is that this only makes sense with TCP/TCP_NIO. Using this with UDP will probably result in worse performance since a single broadcast would be better. Thoughts? -- Manik Surtani Lead, JBoss Cache JBoss, a division of Red Hat Email: manik(a)jboss.org Telephone: +44 7786 702 706 MSN: manik(a)surtani.org Yahoo/AIM/Skype: maniksurtani