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https://issues.apache.org/jira/browse/ZOOKEEPER-3756?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17065017#comment-17065017
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Lasaro Camargos edited comment on ZOOKEEPER-3756 at 3/23/20, 6:56 PM:
----------------------------------------------------------------------

Dear all,

currently, I am consistently facing the following scenario while running 3.5.5 
and 3.5.7, which I believe is related to this bug:

3 nodes up.
 Node 3 stop -> node 2 is elected; node 1 follows.
 Node 3 start -> node 3 elected the leader; node 2 follows; node 1 is unable to 
elect.

Node 1 stop and start -> node 1 rejoins the quorum.
 Node 2 stop and start -> node 2 is unable to elect.
 Node 1 stop and start -> node 2 joins the quorum; node 1 joins the quorum
 Node 2 stop and start -> node 2 unable to join the quorum
 Node 3 stop and start -> node 3 elected the leader; node 2 follows; node 1 is 
unable to elect.

Reducing the cnxTimeout value didn't change the behavior.

I tested with this fix and now it is now worse; after a round of restarts, 
there doesn't seem to have anything I can to make node 1 join finish the 
election.

This is such a nasty problem that I am wondering if there is something else to 
it. Maybe my configuration. Could you point me what would be useful in terms of 
information in order to debug this better? Full logs?

 


was (Author: lasaro):
Dear all,

currently, I am consistently facing the following scenario while running 3.5.5 
and 3.5.7, which I believe is related to this bug:

3 nodes up.
Node 3 stop -> node 2 is elected; node 1 follows.
Node 3 start -> node 3 elected the leader; node 2 follows; node 1 is unable to 
elect.

Node 1 stop and start -> node 1 rejoins the quorum.
Node 2 stop and start -> node 2 is unable to elect.
Node 1 stop and start -> node 2 joins the quorum; node 1 joins the quorum
Node 2 stop and start -> node 2 unable to join the quorum
Node 3 stop and start -> node 3 elected the leader; node 2 follows; node 1 is 
unable to elect.

Reducing the cnxTimeout value didn't change the behavior.

I tested with this fix and now it is now worse; after a round of restarts, 
there doesn't seem to have anything I can to make node 1 join finish the 
election.

 

> Members failing to rejoin quorum
> --------------------------------
>
>                 Key: ZOOKEEPER-3756
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-3756
>             Project: ZooKeeper
>          Issue Type: Improvement
>          Components: leaderElection
>    Affects Versions: 3.5.6, 3.5.7
>            Reporter: Dai Shi
>            Assignee: Mate Szalay-Beko
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 3.6.1
>
>         Attachments: Dockerfile, configmap.yaml, docker-entrypoint.sh, 
> jmx.yaml, zoo-0.log, zoo-1.log, zoo-2.log, zoo-service.yaml, zookeeper.yaml
>
>          Time Spent: 3h
>  Remaining Estimate: 0h
>
> Not sure if this is the place to ask, please close if it's not.
> I am seeing some behavior that I can't explain since upgrading to 3.5:
> In a 5 member quorum, when server 3 is the leader and each server has this in 
> their configuration: 
> {code:java}
> server.1=100.71.255.254:2888:3888:participant;2181
> server.2=100.71.255.253:2888:3888:participant;2181
> server.3=100.71.255.252:2888:3888:participant;2181
> server.4=100.71.255.251:2888:3888:participant;2181
> server.5=100.71.255.250:2888:3888:participant;2181{code}
> If servers 1 or 2 are restarted, they fail to rejoin the quorum with this in 
> the logs:
> {code:java}
> 2020-03-11 20:23:35,720 [myid:2] - INFO  
> [QuorumPeer[myid=2](plain=0.0.0.0:2181)(secure=disabled):QuorumPeer@1175] - 
> LOOKING
> 2020-03-11 20:23:35,721 [myid:2] - INFO  
> [QuorumPeer[myid=2](plain=0.0.0.0:2181)(secure=disabled):FastLeaderElection@885]
>  - New election. My id =  2, proposed zxid=0x1b8005f4bba
> 2020-03-11 20:23:35,733 [myid:2] - INFO  
> [WorkerSender[myid=2]:QuorumCnxManager@438] - Have smaller server identifier, 
> so dropping the connection: (3, 2)
> 2020-03-11 20:23:35,734 [myid:2] - INFO  
> [0.0.0.0/0.0.0.0:3888:QuorumCnxManager$Listener@924] - Received connection 
> request 100.126.116.201:36140
> 2020-03-11 20:23:35,735 [myid:2] - INFO  
> [WorkerSender[myid=2]:QuorumCnxManager@438] - Have smaller server identifier, 
> so dropping the connection: (4, 2)
> 2020-03-11 20:23:35,740 [myid:2] - INFO  
> [WorkerSender[myid=2]:QuorumCnxManager@438] - Have smaller server identifier, 
> so dropping the connection: (5, 2)
> 2020-03-11 20:23:35,740 [myid:2] - INFO  
> [0.0.0.0/0.0.0.0:3888:QuorumCnxManager$Listener@924] - Received connection 
> request 100.126.116.201:36142
> 2020-03-11 20:23:35,740 [myid:2] - INFO  
> [WorkerReceiver[myid=2]:FastLeaderElection@679] - Notification: 2 (message 
> format version), 2 (n.leader), 0x1b8005f4bba (n.zxid), 0x1 (n.round), LOOKING 
> (n.state), 2 (n.sid), 0x1b8 (n.peerEPoch), LOOKING (my state)0 (n.config 
> version)
> 2020-03-11 20:23:35,742 [myid:2] - WARN  
> [SendWorker:3:QuorumCnxManager$SendWorker@1143] - Interrupted while waiting 
> for message on queue
> java.lang.InterruptedException
>         at 
> java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.reportInterruptAfterWait(AbstractQueuedSynchronizer.java:2014)
>         at 
> java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitNanos(AbstractQueuedSynchronizer.java:2088)
>         at 
> java.util.concurrent.ArrayBlockingQueue.poll(ArrayBlockingQueue.java:418)
>         at 
> org.apache.zookeeper.server.quorum.QuorumCnxManager.pollSendQueue(QuorumCnxManager.java:1294)
>         at 
> org.apache.zookeeper.server.quorum.QuorumCnxManager.access$700(QuorumCnxManager.java:82)
>         at 
> org.apache.zookeeper.server.quorum.QuorumCnxManager$SendWorker.run(QuorumCnxManager.java:1131)
> 2020-03-11 20:23:35,744 [myid:2] - WARN  
> [SendWorker:3:QuorumCnxManager$SendWorker@1153] - Send worker leaving thread  
> id 3 my id = 2
> 2020-03-11 20:23:35,745 [myid:2] - WARN  
> [RecvWorker:3:QuorumCnxManager$RecvWorker@1230] - Interrupting 
> SendWorker{code}
> The only way I can seem to get them to rejoin the quorum is to restart the 
> leader.
> However, if I remove server 4 and 5 from the configuration of server 1 or 2 
> (so only servers 1, 2, and 3 remain in the configuration file), then they can 
> rejoin the quorum fine. Is this expected and am I doing something wrong? Any 
> help or explanation would be greatly appreciated. Thank you.



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