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https://issues.apache.org/jira/browse/HDFS-7060?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16240291#comment-16240291
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Weiwei Yang commented on HDFS-7060:
-----------------------------------
Hi [~goirix]
Thanks for commenting on this issue. The patch was original posted by
[~brahmareddy] and we applied to our production cluster then rebased to trunk
as 003 patch. My colleague [~yangjiandan] and I have reviewed the patch and
agreed following
# {{FsDatasetImpl#statsLock}} is only synchronized on a bunch of read
operations, and these values returned from {{FsVolumeList}} are thread safe so
it is not necessary
# Changes in {{FsVolumeImpl}} removes unnecessary dataset locks because all
those metrics operated are atomic. This helps to minimize the locking in HB
path which reduces the HB latency a lot.
for short change #1 is nice to have and change #2 is where the magic happens.
Hope this makes sense to you and let me know your thought. Thanks.
> 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, HDFS-7060.003.patch, HDFS-7060.004.patch,
> complete_failed_qps.png, sendHeartbeat.png
>
>
> 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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