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Re: [Cluster-devel] disallowed in cluster3



On Thu, Aug 06, 2009 at 08:08:37AM +0100, Christine Caulfield wrote:
> On 05/08/09 17:52, David Teigland wrote:
> >When rewriting daemons for cluster3 to remove groupd, I wrote them to not 
> >need
> >or use the disallowed-nodes feature from cman for handling remerging of
> >cluster partitions.  In compat mode, however, (the cluster2 code) they 
> >would
> >still depend on that cman feature, which is why it still exists in cluster3
> >cman.
> >
> >I've found, though, that when we do have a partition remerge, cman's
> >disallowed feature gets in the way of the daemons trying to handle it
> >themselves (which I'm testing, it doesn't seem quite right in all
> >partitioning/merging cases yet.)
> >
> >So, I think what we need is for cluster3 cman to turn off the disallowed
> >feature unless the cluster is in compat mode, i.e.<group 
> >groupd_compat="1"/>
> >exists.
> 
> 
> Thanks, I've been looking for an excuse to add code to cluster3 to 
> disable that mode ;-)

Trying this out and testing the daemon's handling of partition merging
situations...  I uncovered one of my own comments in fenced:

/* We don't require cman dirty/disallowed to detect and handle cpg merges
after a partition, because we already do that with started_count checks and
our own disallowed flag.  But, we do need cman dirty/disallowed to deal with
correctly skipping victims that rejoin the cluster.  Without cman
dirty/disallowed, we'd skip fencing a node after a merge of a partition since
the merged node would be a cman member and a fenced:daemon cpg member.  By
setting the dirty flag, cman won't report a dirty merged node as a member, so
we'll continue fencing it. */

So, the primary reason for cman disallowed is gone, but I'd forgotten about
this little unsolved detail around bypassing fencing of a node that has
rebooted and rejoined (distinguishing that from partitioned and rejoined).
There really should be a way for fenced to deal with that without punting it
off to cman disallowed, I'll be working on that.

Dave


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