[jira] [Updated] (ZOOKEEPER-1237) ERRORs being logged when queued responses are sent after socket has closed.

["Chris Seawood (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ZOOKEEPER-1237?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Chris Seawood updated ZOOKEEPER-1237:
-------------------------------------

    Attachment: zookeeper-3.4.5-ZK1237.patch

This patch downgrades the EndOfStream Exception to a debug message.  It also adds .isValid() checks to avoid the CancelledKeyException.

At a glance, the real problem appears to be that there's no way for the client to deregister itself from the server via the C API.  According to zookeeper.h, calling zookeeper_close() is supposed to close the filehandle and free up resources (presumably on the client side) but afaict, there's nothing on the server side to acknowledge that a client has legitimately disconnected.  In NIOServerCnxn.java, there's even a comment to the effect that when the server initiates a disconnect, it only closes the socket and then lets the doIO() routine clean things up, which results in the additional exceptions being thrown.

                
> ERRORs being logged when queued responses are sent after socket has closed.
> ---------------------------------------------------------------------------
>
>                 Key: ZOOKEEPER-1237
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1237
>             Project: ZooKeeper
>          Issue Type: Bug
>          Components: server
>    Affects Versions: 3.3.4, 3.4.0, 3.5.0
>            Reporter: Patrick Hunt
>             Fix For: 3.5.0
>
>         Attachments: zookeeper-3.4.5-ZK1237.patch
>
>
> After applying ZOOKEEPER-1049 to 3.3.3 (I believe the same problem exists in 3.4/3.5 but haven't tested this) I'm seeing the following exception more frequently:
> {noformat}
> Oct 19, 1:31:53 PM ERROR
> Unexpected Exception:
> java.nio.channels.CancelledKeyException
> at sun.nio.ch.SelectionKeyImpl.ensureValid(SelectionKeyImpl.java:55)
> at sun.nio.ch.SelectionKeyImpl.interestOps(SelectionKeyImpl.java:59)
> at org.apache.zookeeper.server.NIOServerCnxn.sendBuffer(NIOServerCnxn.java:418)
> at org.apache.zookeeper.server.NIOServerCnxn.sendResponse(NIOServerCnxn.java:1509)
> at org.apache.zookeeper.server.FinalRequestProcessor.processRequest(FinalRequestProcessor.java:367)
> at org.apache.zookeeper.server.quorum.CommitProcessor.run(CommitProcessor.java:73)
> {noformat}
> This is a long standing problem where we try to send a response after the socket has been closed. Prior to ZOOKEEPER-1049 this issues happened much less frequently (2 sec linger), but I believe it was possible. The timing window is just wider now.

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