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From "Nathan Roberts (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-7060) Avoid taking locks when sending heartbeats from the DataNode
Date Fri, 20 Nov 2015 21:21:11 GMT

    [ https://issues.apache.org/jira/browse/HDFS-7060?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15018828#comment-15018828
] 

Nathan Roberts commented on HDFS-7060:
--------------------------------------

Has anyone given any further thought on this patch? It seems safe to me and it eliminates
serious stability issues when datanodes' disks get very busy. _getUsed()_ returns a value
that is calculated by a DU process that ran for a long time anyway, (so it's always somewhat
out-of-sync). It's not very difficult to load up a datanode with disk-intensive tasks that
prevent the datanode from getting a heartbeat in for several minutes, eventually being declared
dead by the NN. We've seen this take out entire clusters with large Map/Reduce merges, as
well as very large shuffles. 

> Avoid taking locks when sending heartbeats from the DataNode
> ------------------------------------------------------------
>
>                 Key: HDFS-7060
>                 URL: https://issues.apache.org/jira/browse/HDFS-7060
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>            Reporter: Haohui Mai
>            Assignee: Xinwei Qin 
>              Labels: BB2015-05-TBR
>         Attachments: HDFS-7060-002.patch, HDFS-7060.000.patch, HDFS-7060.001.patch
>
>
> We're seeing the heartbeat is blocked by the monitor of {{FsDatasetImpl}} when the DN
is under heavy load of writes:
> {noformat}
>    java.lang.Thread.State: BLOCKED (on object monitor)
>         at org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsVolumeImpl.getDfsUsed(FsVolumeImpl.java:115)
>         - waiting to lock <0x0000000780304fb8> (a org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetImpl)
>         at org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetImpl.getStorageReports(FsDatasetImpl.java:91)
>         - locked <0x0000000780612fd8> (a java.lang.Object)
>         at org.apache.hadoop.hdfs.server.datanode.BPServiceActor.sendHeartBeat(BPServiceActor.java:563)
>         at org.apache.hadoop.hdfs.server.datanode.BPServiceActor.offerService(BPServiceActor.java:668)
>         at org.apache.hadoop.hdfs.server.datanode.BPServiceActor.run(BPServiceActor.java:827)
>         at java.lang.Thread.run(Thread.java:744)
>    java.lang.Thread.State: BLOCKED (on object monitor)
>         at org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetImpl.createRbw(FsDatasetImpl.java:743)
>         - waiting to lock <0x0000000780304fb8> (a org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetImpl)
>         at org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetImpl.createRbw(FsDatasetImpl.java:60)
>         at org.apache.hadoop.hdfs.server.datanode.BlockReceiver.<init>(BlockReceiver.java:169)
>         at org.apache.hadoop.hdfs.server.datanode.DataXceiver.writeBlock(DataXceiver.java:621)
>         at org.apache.hadoop.hdfs.protocol.datatransfer.Receiver.opWriteBlock(Receiver.java:124)
>         at org.apache.hadoop.hdfs.protocol.datatransfer.Receiver.processOp(Receiver.java:71)
>         at org.apache.hadoop.hdfs.server.datanode.DataXceiver.run(DataXceiver.java:232)
>         at java.lang.Thread.run(Thread.java:744)
>    java.lang.Thread.State: RUNNABLE
>         at java.io.UnixFileSystem.createFileExclusively(Native Method)
>         at java.io.File.createNewFile(File.java:1006)
>         at org.apache.hadoop.hdfs.server.datanode.DatanodeUtil.createTmpFile(DatanodeUtil.java:59)
>         at org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.BlockPoolSlice.createRbwFile(BlockPoolSlice.java:244)
>         at org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsVolumeImpl.createRbwFile(FsVolumeImpl.java:195)
>         at org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetImpl.createRbw(FsDatasetImpl.java:753)
>         - locked <0x0000000780304fb8> (a org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetImpl)
>         at org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetImpl.createRbw(FsDatasetImpl.java:60)
>         at org.apache.hadoop.hdfs.server.datanode.BlockReceiver.<init>(BlockReceiver.java:169)
>         at org.apache.hadoop.hdfs.server.datanode.DataXceiver.writeBlock(DataXceiver.java:621)
>         at org.apache.hadoop.hdfs.protocol.datatransfer.Receiver.opWriteBlock(Receiver.java:124)
>         at org.apache.hadoop.hdfs.protocol.datatransfer.Receiver.processOp(Receiver.java:71)
>         at org.apache.hadoop.hdfs.server.datanode.DataXceiver.run(DataXceiver.java:232)
>         at java.lang.Thread.run(Thread.java:744)
> {noformat}



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