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https://issues.apache.org/jira/browse/ZOOKEEPER-1869?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14737125#comment-14737125
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Raul Gutierrez Segales commented on ZOOKEEPER-1869:
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Also, 3.5.1 (though alpha, but being used by many) is now available as well:
http://zookeeper.apache.org/doc/r3.5.1-alpha/releasenotes.html
> zk server falling apart from quorum due to connection loss and couldn't
> connect back
> ------------------------------------------------------------------------------------
>
> Key: ZOOKEEPER-1869
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1869
> Project: ZooKeeper
> Issue Type: Bug
> Components: quorum
> Affects Versions: 3.5.0
> Environment: Using CentOS6 for running these zookeeper servers
> Reporter: Deepak Jagtap
> Priority: Critical
>
> We have deployed zookeeper version 3.5.0.1515976, with 3 zk servers in the
> quorum.
> The problem we are facing is that one zookeeper server in the quorum falls
> apart, and never becomes part of the cluster until we restart zookeeper
> server on that node.
> Our interpretation from zookeeper logs on all nodes is as follows:
> (For simplicity assume S1=> zk server1, S2 => zk server2, S3 => zk server 3)
> Initially S3 is the leader while S1 and S2 are followers.
> S2 hits 46 sec latency while fsyncing write ahead log and results in loss of
> connection with S3.
> S3 in turn prints following error message:
> Unexpected exception causing shutdown while sock still open
> java.net.SocketTimeoutException: Read timed out
> Stack trace
> ******* GOODBYE /169.254.1.2:47647(S2) ********
> S2 in this case closes connection with S3(leader) and shuts down follower
> with following log messages:
> Closing connection to leader, exception during packet send
> java.net.SocketException: Socket close
> Follower@194] - shutdown called
> java.lang.Exception: shutdown Follower
> After this point S3 could never reestablish connection with S2 and leader
> election mechanism keeps failing. S3 now keeps printing following message
> repeatedly:
> Cannot open channel to 2 at election address /169.254.1.2:3888
> java.net.ConnectException: Connection refused.
> While S3 is in this state, S2 repeatedly keeps printing following message:
> INFO
> [NIOServerCxnFactory.AcceptThread:/0.0.0.0:2181:NIOServerCnxnFactory$AcceptThread@296]
> - Accepted socket connection from /127.0.0.1:60667
> Exception causing close of session 0x0: ZooKeeperServer not running
> Closed socket connection for client /127.0.0.1:60667 (no session established
> for client)
> Leader election never completes successfully and causing S2 to fall apart
> from the quorum.
> S2 was out of quorum for almost 1 week.
> While debugging this issue, we found out that both election and peer
> connection ports on S2 can't be telneted from any of the node (S1, S2, S3).
> Network connectivity is not the issue. Later, we restarted the ZK server S2
> (service zookeeper-server restart) -- now we could telnet to both the ports
> and S2 joined the ensemble after a leader election attempt.
> Any idea what might be forcing S2 to get into a situation where it won't
> accept any connections on the leader election and peer connection ports?
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