Patrick Hunt commented on ZOOKEEPER-914:

Thanks for the bug report. I've yet to find a codebase where I couldn't find 
what I consider "bad programming", so I don't find that a constructive comment. 
We're happy you've joined community, let's all work together to address these 
issues. Thanks.

bq. points out to lack of failure tests for QuorumCnxManager

We can always use more testing. If you want to contribute additional patches 
just for testing please do so (I'm sure if you talk with Flavio he could give 
you some good ideas). Notice that there are a number of tests exercising this 
code already (around 85% coverage), we'd need to figure out some way to 
simulate network failures and such, which is difficult in my experience:

> QuorumCnxManager blocks forever 
> --------------------------------
>                 Key: ZOOKEEPER-914
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-914
>             Project: Zookeeper
>          Issue Type: Bug
>            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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