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https://issues.apache.org/jira/browse/ZOOKEEPER-126?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13114934#comment-13114934
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Daniel Lord commented on ZOOKEEPER-126:
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Hey guys, I just ran in to a cascading failure that ended up settling on this.
The issue was my SendThread was killed by an NPE when trying to log some
unknown exception. The line that caused the SendThread to die was:
at org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1161)
This is using zookeeper 3.3.2. The NPE from the logging ends up killing the
SendThread by an uncaught exception. Eventually the lack of a send thread
causes the client to disconnect/expire. At this point the zookeeper client is
close()'d. The close call will hang forever because the final packet is never
sent so it is never ACK'd or notify()'d and we stall out forever.
Should this NPE be filed as a new issue or are you all content that this timed
close will solve the problem?
> zookeeper client close operation may block indefinitely
> -------------------------------------------------------
>
> Key: ZOOKEEPER-126
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-126
> Project: ZooKeeper
> Issue Type: Bug
> Components: java client
> Reporter: Patrick Hunt
> Fix For: 3.5.0
>
> Attachments: ZOOKEEPER-126.patch, ZOOKEEPER-126.patch
>
>
> Moving the hang issue from ZOOKEEPER-63 to here. See 63 for background and
> potential patch (patch_ZOOKEEPER-63.patch).
> specifically (from James):
> "I'm thinking the close() method should not wait() forever on the disconnect
> packet, just a closeTimeout length - say a few seconds. Afterall blocking and
> forcing a reconnect just to redeliver the disconnect packet seems a bit silly
> - when the server has to deal with clients which just have their sockets fail
> anyway"
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