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Date: Tue, 03 Nov 2009 08:53:03 -0500
From: Carl Trieloff <cctrieloff@redhat.com>
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Subject: Re: An ill borker brings down the whole cluster
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I don't have enough info to comment on the root cause, Maybe Alan can 
based on the log snippet, however there is a pulg-in module that can be 
run on nodes in a cluster that will
remove any stalled node in the cluster so that the rest of the cluster 
can continue to operate as normal.

For example, if you sig-stop one broker in a cluster, then the rest of 
teh cluster will continue to run, but AIS will cache for the node that 
is stopped. It is required that node be evicted at some point if it does 
not get a sig-cont after a period of time. The watchdog plugin does this 
for you, at which point you can rejoin another node.

i.e. running the watchdog would have removed the un-responsive broker in 
your example below.  The second part is to understand why it was 
unresponsive.

Carl.


Shan Wang wrote:
> Hi All,
>
> We have two qpid 0.5 brokers running in cluster mode on two different boxes. The cluster works fine in normal cases, ie, if broker1 is shutdown cleanly, broker2 will keep on serving clients. But today we found one broker suddenly lost response to all connected clients and admin tools. All producer and consumer clients are still connected but failed to consume any messages from the queue. The command line admin tool failed with a time out error. The only error message we found is in the log of broker 1, which said this:
>
> 2009-oct-31 10:17:49 error 172.27.34.201:9908(READY/error) channel error 157487219 on 172.27.34.201:9908-389(local): transport-busy: Channel 1 already attached to guest@QPID.amq.failover676a76fa-56
> 64-4e49-9bee-0538532fe261 (qpid/amqp_0_10/SessionHandler.cpp:150) (unresolved: 172.27.34.201:9908 172.27.34.202:13287 )
>
> After only restarted broker 1, everything starts to work again. So surprisingly it seems when one of the brokers in the cluster suffered a problem, the whole cluster just stalled, at least from the consumer's point of view ( I can't be sure if the producer was working during the down time, after back to normal, consumer did receive messages sent sometime ago ). Consumer program uses FailoverManager and AsyncSession, basically not far from the failover example in the qpid developing doc. So can anyone please tell me what the above error message means and have we seen similar problems to the cluster before?
>
>
> Regards,
> Shan
>
>
>
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