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Date: Wed, 12 Feb 2014 11:14:52 -0800
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Subject: Re: zookeeper quorum falling apart with continuous leader election
From: Deepak Jagtap <deepak.jagtap@maxta.com>
To: user@zookeeper.apache.org
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Thanks Flavio for quick repsonse!
Yes, logs for third node with bad disk are missing.

Hi Kishore, zk client completely lost the connection to zookeeper so most
probably there are no writes on the system. But on node 2 (Leader) I saw
some log message indicating successful session establishment from client,
hence possibility of writes on the server can not be ignored.

Thanks & Regards,
Deepak


On Wed, Feb 12, 2014 at 9:56 AM, kishore g <g.kishore@gmail.com> wrote:

> Just for my understanding what do these messages indicate.  Also I see that
> n.zxid keeps incrementing, does it mean the system is accepting writes?
>
> node 2
> 2014-02-10 19:49:06,860 [myid:235] - INFO
> [WorkerReceiver[myid=235]:FastLeaderElection@594] - Notification: 234
> (n.leader), 0x4afe00000001 (n.zxid), 0x4b00 (n.round), LOOKING (n.state),
> 234 (n.sid), 0x4aff (n.peerEPoch), LOOKING (my state)1 (n.config version)
>
> node 1
> 2014-02-10 19:42:02,936 [myid:234] - INFO
> [WorkerReceiver[myid=234]:FastLeaderElection@594] - Notification: 234
> (n.leader), 0x4afa00000001 (n.zxid), 0x4afc (n.round), LOOKING (n.state),
> 234 (n.sid), 0x4afb (n.peerEPoch), LOOKING (my state)1 (n.config version)
>
>
>
>
> On Wed, Feb 12, 2014 at 6:47 AM, Flavio Junqueira <fpjunqueira@yahoo.com
> >wrote:
>
> > It sounds like LE is completing periodically, but the servers are not
> > being able to complete the synchronization step. We are also getting this
> > connection refused exception when the follower is trying to connect. This
> > is what I spotted for the follower:
> >
> > 2014-02-10 18:54:04,414 [myid:234] - INFO
> >  [QuorumPeer[myid=234]/0:0:0:0:0:0:0:0:2181:Follower@65] - FOLLOWING -
> > LEADER ELECTION TOOK - 1
> > 2014-02-10 18:54:04,415 [myid:234] - WARN
> >  [QuorumPeer[myid=234]/0:0:0:0:0:0:0:0:2181:Learner@239] - Unexpected
> > exception, tries=0, connecting to 10.0.57.235/10.0.57.235:2888
> > java.net.ConnectException: Connection refused
> >         at java.net.PlainSocketImpl.socketConnect(Native Method)
> >         at java.net.AbstractPlainSocketImpl.doConnect(Unknown Source)
> >         at java.net.AbstractPlainSocketImpl.connectToAddress(Unknown
> > Source)
> >         at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
> >         at java.net.SocksSocketImpl.connect(Unknown Source)
> >         at java.net.Socket.connect(Unknown Source)
> >         at
> >
> org.apache.zookeeper.server.quorum.Learner.connectToLeader(Learner.java:231)
> >         at
> >
> org.apache.zookeeper.server.quorum.Follower.followLeader(Follower.java:73)
> >         at
> > org.apache.zookeeper.server.quorum.QuorumPeer.run(QuorumPeer.java:936)
> >
> > and this:
> >
> > 2014-02-10 18:55:05,508 [myid:234] - INFO
> >  [QuorumPeer[myid=234]/0:0:0:0:0:0:0:0:2181:Learner@442] - Learner
> > received UPTODATE message
> > 2014-02-10 18:55:05,508 [myid:234] - WARN
> >  [QuorumPeer[myid=234]/0:0:0:0:0:0:0:0:2181:Follower@92] - Exception
> when
> > following the leader
> > java.net.SocketException: Broken pipe
> >         at java.net.SocketOutputStream.socketWrite0(Native Method)
> >         at java.net.SocketOutputStream.socketWrite(Unknown Source)
> >         at java.net.SocketOutputStream.write(Unknown Source)
> >         at java.io.BufferedOutputStream.flushBuffer(Unknown Source)
> >         at java.io.BufferedOutputStream.flush(Unknown Source)
> >         at
> > org.apache.zookeeper.server.quorum.Learner.writePacket(Learner.java:145)
> >         at
> >
> org.apache.zookeeper.server.quorum.Learner.syncWithLeader(Learner.java:477)
> >         at
> >
> org.apache.zookeeper.server.quorum.Follower.followLeader(Follower.java:85)
> >         at
> > org.apache.zookeeper.server.quorum.QuorumPeer.run(QuorumPeer.java:936)
> >
> > On the leader side, we have this:
> >
> > 2014-02-10 19:48:03,705 [myid:235] - INFO
> >  [LearnerHandler-/10.0.57.234:58829:LearnerHandler@328] - Synchronizing
> > with Follower sid: 234 maxCommittedLog=0x4afe00000001
> > minCommittedLog=0x4afe00000001 peerLastZxid=0x4afd00000001
> > 2014-02-10 19:48:03,705 [myid:235] - WARN
> >  [LearnerHandler-/10.0.57.234:58829:LearnerHandler@389] - Unhandled
> > proposal scenario
> > 2014-02-10 19:48:03,705 [myid:235] - INFO
> >  [LearnerHandler-/10.0.57.234:58829:LearnerHandler@404] - Sending SNAP
> > 2014-02-10 19:48:03,705 [myid:235] - INFO
> >  [LearnerHandler-/10.0.57.234:58829:LearnerHandler@435] - Sending
> > snapshot last zxid of peer is 0x4afd00000001  zxid of leader is
> > 0x4aff00000000sent zxid of db as 0x4afe00000001
> > 2014-02-10 19:48:03,724 [myid:235] - WARN
> >  [LearnerHandler-/10.0.57.234:58829:Leader@698] - Commiting zxid
> > 0x4aff00000000 from /10.0.57.235:2888 not first!
> >
> > There are a couple of odd warnings there. Just to confirm, the node
> > missing in the logs is the one with the bad disk, right?
> >
> > -Flavio
> >
> > On 12 Feb 2014, at 02:26, Deepak Jagtap <deepak.jagtap@maxta.com> wrote:
> >
> > > Hi ,
> > >
> > > I have 3 node zookeeper 3.5.0.1458648 quorum on my setup.
> > > We came across a situation where one of the zk server in the cluster
> went
> > > down
> > > due to bad disk.
> > > We observed that leader election keeps running in loop (starts,
> completes
> > > and again starts). The loop repeats every couple of minutes.
> > > Even restarting zookeeper server on both nodes doesn't help recovering
> > from
> > > this loop.
> > > Network connection looks fine though, as I could telnet leader election
> > > port and ssh from one node to other.
> > > zookeeper client on each node is using "127.0.0.1:2181" as quorum
> string
> > > for connecting to server, therefore if local zookeeper server is down
> > > client app is dead.
> > >
> > > I have uploaded zookeeper.log for both nodes at following link:
> > > https://dl.dropboxusercontent.com/u/36429721/zkSupportLog.tar.gz
> > >
> > > Any idea what might be wrong with the quorum? Please note that
> restarting
> > > zookeeper server on both nodes doesn't help to recover from this
> > situations.
> > >
> > > Thanks & Regards,
> > > Deepak
> >
> >
>

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