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https://issues.apache.org/jira/browse/HDFS-7060?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15215413#comment-15215413
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John Zhuge commented on HDFS-7060:
----------------------------------
If we assume dataset lock protects {{bpSlices}}. The following functions access
{{bpSlices}} but they and their callers do NOT lock dataset. Did I miss
anything? Is this a bug?
{code}
FsVolumeImpl#addBlockPool (this is a write access to bpSlices)
FsVolumeImpl#addBlockPool
FsDatasetImpl#addVolume
FsVolumeImpl#getBlockPoolUsed
FsVolumeList#getBlockPoolUsed
FsDatasetImpl#getBlockPoolUsed
FsVolumeImpl#getBlockPoolSlice
(too many callers, hard to track down !)
FsVolumeImpl#getBlockPoolList
DirectoryScanner.ReportCompiler#call
FsVolumeImpl#checkDirs
FsVolumeImpl#checkDirs
FsDatasetImpl#checkDataDir
...
{code}
A few suggestions regarding lock usage:
* All locks including intrinsic locks should include docs that clearly state
what resources they protect.
* Locks should be used in the classes they are defined. Very hard to reason if
their usages are scattered around.
If we want to protect {{bpSlices}} with lock, can we just use {{bpSlices}}
intrinsic lock instead of dataset lock?
> 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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