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Re: [Linux-cluster] Multicast for GFS?



On Mon, Aug 09, 2004 at 01:32:23PM +0200, Lazar Obradovic wrote:
> 
> > You also mentioned in another email that the "cman_tool leave" should issue 
> > a setsockopt to leave the multicast group, does this not happen automatically 
> > when the socket is closed? 
> 
> Actually no. When you close the socket that was a member of Mcast Group,
> node does not sent "IGMP leave" message to router, so mcast packets
> continue to arrive until router issues "membership refresh" procedure
> (which, depending on configuration, is at every 30 seconds). 
> 
> If node does not confirm it's membership (and it won't since kernel
> can't find any socket for the multicast group), mcast path gets pruned
> at a router, but stays valid for another 2-3 minutes (also depending on
> configuration).
> 
> > If it isn't then cman_tool leave can do this I
> > suppose. In the case where the cluster software exits without the help of
> > cman_tool it will be fenced anyway so there shoudn't be a problem :-)
> 
> That's true for fenced nodes, but it's not a clean solution, so, if it
> isn't much of a trouble, I'd really like to have membership drop
> implemented before socket gets closed.
> 

OK, thanks for clearing that up. It seems I have some thinking to do...


patrick


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