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Date: Fri, 29 May 2015 15:19:26 +0000 (UTC)
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Subject: [jira] [Commented] (HDFS-8429) Avoid stuck threads if there is an
 error in DomainSocketWatcher that stops the thread
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    [ https://issues.apache.org/jira/browse/HDFS-8429?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14564957#comment-14564957 ] 

Hudson commented on HDFS-8429:
------------------------------

SUCCESS: Integrated in Hadoop-Mapreduce-trunk-Java8 #210 (See [https://builds.apache.org/job/Hadoop-Mapreduce-trunk-Java8/210/])
HDFS-8429. Avoid stuck threads if there is an error in DomainSocketWatcher that stops the thread.  (zhouyingchao via cmccabe) (cmccabe: rev 246cefa089156a50bf086b8b1e4d4324d66dc58c)
* hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/net/unix/DomainSocketWatcher.java
* hadoop-common-project/hadoop-common/CHANGES.txt
* hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/net/unix/TestDomainSocketWatcher.java
* hadoop-common-project/hadoop-common/src/main/native/src/org/apache/hadoop/net/unix/DomainSocketWatcher.c


> Avoid stuck threads if there is an error in DomainSocketWatcher that stops the thread
> -------------------------------------------------------------------------------------
>
>                 Key: HDFS-8429
>                 URL: https://issues.apache.org/jira/browse/HDFS-8429
>             Project: Hadoop HDFS
>          Issue Type: Bug
>    Affects Versions: 2.6.0
>            Reporter: zhouyingchao
>            Assignee: zhouyingchao
>             Fix For: 2.8.0
>
>         Attachments: HDFS-8429-001.patch, HDFS-8429-002.patch, HDFS-8429-003.patch
>
>
> In our cluster, an application is hung when doing a short circuit read of local hdfs block. By looking into the log, we found the DataNode's DomainSocketWatcher.watcherThread has exited with following log:
> {code}
> ERROR org.apache.hadoop.net.unix.DomainSocketWatcher: Thread[Thread-25,5,main] terminating on unexpected exception
> java.lang.NullPointerException
>         at org.apache.hadoop.net.unix.DomainSocketWatcher$2.run(DomainSocketWatcher.java:463)
>         at java.lang.Thread.run(Thread.java:662)
> {code}
> The line 463 is following code snippet:
> {code}
>          try {
>             for (int fd : fdSet.getAndClearReadableFds()) {
>               sendCallbackAndRemove("getAndClearReadableFds", entries, fdSet,
>                 fd);
>             }
> {code}
> getAndClearReadableFds is a native method which will malloc an int array. Since our memory is very tight, it looks like the malloc failed and a NULL pointer is returned.
> The bad thing is that other threads then blocked in stack like this:
> {code}
> "DataXceiver for client unix:/home/work/app/hdfs/c3prc-micloud/datanode/dn_socket [Waiting for operation #1]" daemon prio=10 tid=0x00007f0c9c086d90 nid=0x8fc3 waiting on condition [0x00007f09b9856000]
>    java.lang.Thread.State: WAITING (parking)
>         at sun.misc.Unsafe.park(Native Method)
>         - parking to wait for  <0x00000007b0174808> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
>         at java.util.concurrent.locks.LockSupport.park(LockSupport.java:156)
>         at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:1987)
>         at org.apache.hadoop.net.unix.DomainSocketWatcher.add(DomainSocketWatcher.java:323)
>         at org.apache.hadoop.hdfs.server.datanode.ShortCircuitRegistry.createNewMemorySegment(ShortCircuitRegistry.java:322)
>         at org.apache.hadoop.hdfs.server.datanode.DataXceiver.requestShortCircuitShm(DataXceiver.java:403)
>         at org.apache.hadoop.hdfs.protocol.datatransfer.Receiver.opRequestShortCircuitShm(Receiver.java:214)
>         at org.apache.hadoop.hdfs.protocol.datatransfer.Receiver.processOp(Receiver.java:95)
>         at org.apache.hadoop.hdfs.server.datanode.DataXceiver.run(DataXceiver.java:235)
>         at java.lang.Thread.run(Thread.java:662)
> {code}
> IMO, we should exit the DN so that the users can know that something go  wrong  and fix it.


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