[jira] Resolved: (ZOOKEEPER-914) QuorumCnxManager blocks forever

["Vishal K (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ZOOKEEPER-914?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Vishal K resolved ZOOKEEPER-914.
--------------------------------

       Resolution: Duplicate
    Fix Version/s:     (was: 3.3.3)
                       (was: 3.4.0)

Dup of ZOOKEEPER-900.

> QuorumCnxManager blocks forever 
> --------------------------------
>
>                 Key: ZOOKEEPER-914
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-914
>             Project: Zookeeper
>          Issue Type: Bug
>          Components: leaderElection
>            Reporter: Vishal K
>            Assignee: Vishal K
>            Priority: Blocker
>
> This was a disaster. While testing our application we ran into a scenario where a rebooted follower could not join the cluster. Further debugging showed that the follower could not join because the QuorumCnxManager on the leader was blocked for indefinite amount of time in receiveConnect()
> "Thread-3" prio=10 tid=0x00007fa920005800 nid=0x11bb runnable [0x00007fa9275ed000]
>    java.lang.Thread.State: RUNNABLE
>     at sun.nio.ch.FileDispatcher.read0(Native Method)
>     at sun.nio.ch.SocketDispatcher.read(SocketDispatcher.java:21)
>     at sun.nio.ch.IOUtil.readIntoNativeBuffer(IOUtil.java:233)
>     at sun.nio.ch.IOUtil.read(IOUtil.java:206)
>     at sun.nio.ch.SocketChannelImpl.read(SocketChannelImpl.java:236)
>     - locked <0x00007fa93315f988> (a java.lang.Object)
>     at org.apache.zookeeper.server.quorum.QuorumCnxManager.receiveConnection(QuorumCnxManager.java:210)
>     at org.apache.zookeeper.server.quorum.QuorumCnxManager$Listener.run(QuorumCnxManager.java:501)
> I had pointed out this bug along with several other problems in QuorumCnxManager earlier in 
> https://issues.apache.org/jira/browse/ZOOKEEPER-900 and https://issues.apache.org/jira/browse/ZOOKEEPER-822.
> I forgot to patch this one as a part of ZOOKEEPER-822. I am working on a fix and a patch will be out soon. 
> The problem is that QuorumCnxManager is using SocketChannel in blocking mode. It does a read() in receiveConnection() and a write() in initiateConnection().
> Sorry, but this is really bad programming. Also, points out to lack of failure tests for QuorumCnxManager.

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