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https://issues.apache.org/jira/browse/HDFS-7999?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14391504#comment-14391504
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Colin Patrick McCabe commented on HDFS-7999:
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bq. Make the heartbeat lockless can avoid the happening of dead DataNode, and I
think it is a necessary
The heartbeat wasn't lockless in Hadoop 2.1, 2.3, or 2.5. It's clearly not
necessary to make the heartbeat lockless. It may be a good optimization, but
it is not a bug that the heartbeat takes locks.
> FsDatasetImpl#createTemporary sometimes holds the FSDatasetImpl lock for a
> very long time
> -----------------------------------------------------------------------------------------
>
> Key: HDFS-7999
> URL: https://issues.apache.org/jira/browse/HDFS-7999
> Project: Hadoop HDFS
> Issue Type: Bug
> Affects Versions: 2.6.0
> Reporter: zhouyingchao
> Assignee: zhouyingchao
> Attachments: HDFS-7999-001.patch
>
>
> I'm using 2.6.0 and noticed that sometime DN's heartbeat were delayed for
> very long time, say more than 100 seconds. I get the jstack twice and looks
> like they are all blocked (at getStorageReport) by dataset lock, and which is
> held by a thread that is calling createTemporary, which again is blocked to
> wait earlier incarnation writer to exit.
> The heartbeat thread stack:
> java.lang.Thread.State: BLOCKED (on object monitor)
> at
> org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsVolumeImpl.getDfsUsed(FsVolumeImpl.java:152)
> - waiting to lock <0x00000007b01428c0> (a
> org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetImpl)
> at
> org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetImpl.getStorageReports(FsDatasetImpl.java:144)
> - locked <0x00000007b0140ed0> (a java.lang.Object)
> at
> org.apache.hadoop.hdfs.server.datanode.BPServiceActor.sendHeartBeat(BPServiceActor.java:575)
> at
> org.apache.hadoop.hdfs.server.datanode.BPServiceActor.offerService(BPServiceActor.java:680)
> at
> org.apache.hadoop.hdfs.server.datanode.BPServiceActor.run(BPServiceActor.java:850)
> at java.lang.Thread.run(Thread.java:662)
> The DataXceiver thread holds the dataset lock:
> "DataXceiver for client at XXXXX" daemon prio=10 tid=0x00007f14041e6480
> nid=0x52bc in Object.wait() [0x00007f11d78f7000]
> java.lang.Thread.State: TIMED_WAITING (on object monitor)
> at java.lang.Object.wait(Native Method)
> at java.lang.Thread.join(Thread.java:1194)
> locked <0x00000007a33b85d8> (a org.apache.hadoop.util.Daemon)
> at
> org.apache.hadoop.hdfs.server.datanode.ReplicaInPipeline.stopWriter(ReplicaInPipeline.java:183)
> at
> org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetImpl.createTemporary(FsDatasetImpl.java:1231)
> locked <0x00000007b01428c0> (a
> org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetImpl)
> at
> org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetImpl.createTemporary(FsDatasetImpl.java:114)
> at
> org.apache.hadoop.hdfs.server.datanode.BlockReceiver.<init>(BlockReceiver.java:179)
> at
> org.apache.hadoop.hdfs.server.datanode.DataXceiver.writeBlock(DataXceiver.java:615)
> at
> org.apache.hadoop.hdfs.protocol.datatransfer.Receiver.opWriteBlock(Receiver.java:137)
> at
> org.apache.hadoop.hdfs.protocol.datatransfer.Receiver.processOp(Receiver.java:74)
> at
> org.apache.hadoop.hdfs.server.datanode.DataXceiver.run(DataXceiver.java:235)
> at java.lang.Thread.run(Thread.java:662)
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