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https://issues.apache.org/jira/browse/ZOOKEEPER-3266?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16777844#comment-16777844
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maoling commented on ZOOKEEPER-3266:
------------------------------------
[~jiangjiafu]
Any advance?
> ZooKeeper Java client blocks for a very long time.
> --------------------------------------------------
>
> Key: ZOOKEEPER-3266
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-3266
> Project: ZooKeeper
> Issue Type: Bug
> Components: java client
> Affects Versions: 3.4.13
> Reporter: Jiafu Jiang
> Priority: Major
>
> I found that ZooKeeper java client blocked, and the related call stack was
> shown below:
> "Election thread-20" #20 prio=5 os_prio=0 tid=0x00007f7deeadfd80 nid=0x5ec3
> in Object.wait() [0x00007f7ddd5d8000]
> java.lang.Thread.State: WAITING (on object monitor)
> at java.lang.Object.wait(Native Method)
> at java.lang.Object.wait(Object.java:502)
> at org.apache.zookeeper.ClientCnxn.submitRequest(ClientCnxn.java:1411)
> - locked <0x00000000e04b63b0> (a org.apache.zookeeper.ClientCnxn$Packet)
> at org.apache.zookeeper.ZooKeeper.exists(ZooKeeper.java:1177)
> at org.apache.zookeeper.ZooKeeper.exists(ZooKeeper.java:1210)
> at
> com.sugon.parastor.zookeeper.ZooKeeperClient.exists(ZooKeeperClient.java:643)
> ........
>
> And I also found that the block process did not have the SendThread thread.
> It seems like a normal process with ZooKeeper java client should have a
> SendThread, like below:
> "Thread-0-SendThread(ofs_zk1:2181)" #23 daemon prio=5 os_prio=0
> tid=0x00007f8c540379c0 nid=0x739 runnable [0x00007f8c5ad71000]
> java.lang.Thread.State: RUNNABLE
> at sun.nio.ch.EPollArrayWrapper.epollWait(Native Method)
> at sun.nio.ch.EPollArrayWrapper.poll(EPollArrayWrapper.java:269)
> at sun.nio.ch.EPollSelectorImpl.doSelect(EPollSelectorImpl.java:93)
> at sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:86)
> - locked <0x00000000e00287a8> (a sun.nio.ch.Util$3)
> - locked <0x00000000e0028798> (a java.util.Collections$UnmodifiableSet)
> - locked <0x00000000e0028750> (a sun.nio.ch.EPollSelectorImpl)
> at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:97)
> at
> org.apache.zookeeper.ClientCnxnSocketNIO.doTransport(ClientCnxnSocketNIO.java:349)
> at org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1145)
>
> So, will the missing of the SendThread thread cause the blocking of exist
> method?? I'm not sure.
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