[jbosscache-dev] Re: Anycast

[Bela Ban]

Manik Surtani wrote:
> Not the way the RPCDispatcher in JGroups works.  I always pass in a 
> List of buddies, and usually this list would have 1 element (if n=1).  
> Either way, even if n=3 in a 500 node cluster the multicast is 
> inefficient.

Not worse than TCP: in TCP, we send the *same message* 500 times, one 
for each node. Everyone discards the message but the 3 who are targetted.

Not a big problem for now, because we usually have small clusters, but 
something that need fixing in the future.

How the transport delivers a message M to X members of a cluster of size 
N (where X <= N) is left to the transport.

TCP: here, the transport would probably simply send M to X members.
UDP: if X is close to N --> multicast M and everyone whose not in the 
target set X simply discards M. If X is small --> unicast to X

-- 
Bela Ban
Lead JGroups / Manager JBoss Clustering Group
JBoss - a division of Red Hat