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https://issues.apache.org/jira/browse/ZOOKEEPER-2172?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14555672#comment-14555672
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Ziyou Wang commented on ZOOKEEPER-2172:
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Hi Alexander and Michi,
Thanks a lot for looking at this bug. The zk-2031 is developed as a part of our
system. So I cannot remove this patch away to reproduce this problem. I will
try to reproduce this problem with debug log enabled.
BTW. we hit this problems many time after reporting this issue. If we move to a
slower environment, e.g. a nested host, it need more time between start and
reconfig to avoid it. So I suspect it may be caused when the node 3 doesn't
finish sync latest data from leader, the reconfig comes and breaks some thing.
Do you have some idea about this?
For Alexander's quesitons, our system had a bug in such case when reporting
this jira. It just retried to do the reconfig to add node2 even the node 2 is
already in the list. I already fixed it, but we still hit this jira problem
again now.
> Cluster crashes when reconfig a new node as a participant
> ---------------------------------------------------------
>
> Key: ZOOKEEPER-2172
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2172
> Project: ZooKeeper
> Issue Type: Bug
> Components: leaderElection, quorum, server
> Affects Versions: 3.5.0
> Environment: Ubuntu 12.04 + java 7
> Reporter: Ziyou Wang
> Priority: Critical
> Attachments: node-1.log, node-2.log, node-3.log,
> zoo.cfg.dynamic.10000005d, zoo.cfg.dynamic.next
>
>
> The operations are quite simple: start three zk servers one by one, then
> reconfig the cluster to add the new one as a participant. When I add the
> third one, the zk cluster may enter a weird state and cannot recover.
>
> I found “2015-04-20 12:53:48,236 [myid:1] - INFO [ProcessThread(sid:1
> cport:-1)::PrepRequestProcessor@547] - Incremental reconfig” in node-1 log.
> So the first node received the reconfig cmd at 12:53:48. Latter, it logged
> “2015-04-20 12:53:52,230 [myid:1] - ERROR
> [LearnerHandler-/10.0.0.2:55890:LearnerHandler@580] - Unexpected exception
> causing shutdown while sock still open” and “2015-04-20 12:53:52,231 [myid:1]
> - WARN [LearnerHandler-/10.0.0.2:55890:LearnerHandler@595] - ******* GOODBYE
> /10.0.0.2:55890 ********”. From then on, the first node and second node
> rejected all client connections and the third node didn’t join the cluster as
> a participant. The whole cluster was done.
>
> When the problem happened, all three nodes just used the same dynamic
> config file zoo.cfg.dynamic.10000005d which only contained the first two
> nodes. But there was another unused dynamic config file in node-1 directory
> zoo.cfg.dynamic.next which already contained three nodes.
>
> When I extended the waiting time between starting the third node and
> reconfiguring the cluster, the problem didn’t show again. So it should be a
> race condition problem.
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