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Date: Wed, 31 Aug 2016 05:47:21 +0000 (UTC)
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Subject: [jira] [Commented] (HDFS-9668) Optimize the locking in
 FsDatasetImpl
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    [ https://issues.apache.org/jira/browse/HDFS-9668?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15451232#comment-15451232 ] 

Hadoop QA commented on HDFS-9668:
---------------------------------

| (x) *{color:red}-1 overall{color}* |
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|| Vote || Subsystem || Runtime || Comment ||
| {color:blue}0{color} | {color:blue} reexec {color} | {color:blue}  0m  0s{color} | {color:blue} Docker mode activated. {color} |
| {color:red}-1{color} | {color:red} patch {color} | {color:red}  0m  6s{color} | {color:red} HDFS-9668 does not apply to trunk. Rebase required? Wrong Branch? See https://wiki.apache.org/hadoop/HowToContribute for help. {color} |
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|| Subsystem || Report/Notes ||
| JIRA Issue | HDFS-9668 |
| JIRA Patch URL | https://issues.apache.org/jira/secure/attachment/12825945/HDFS-9668-5.patch |
| Console output | https://builds.apache.org/job/PreCommit-HDFS-Build/16589/console |
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> Optimize the locking in FsDatasetImpl
> -------------------------------------
>
>                 Key: HDFS-9668
>                 URL: https://issues.apache.org/jira/browse/HDFS-9668
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: datanode
>            Reporter: Jingcheng Du
>            Assignee: Jingcheng Du
>             Fix For: 3.0.0-alpha2
>
>         Attachments: HDFS-9668-1.patch, HDFS-9668-2.patch, HDFS-9668-3.patch, HDFS-9668-4.patch, HDFS-9668-5.patch, execution_time.png
>
>
> During the HBase test on a tiered storage of HDFS (WAL is stored in SSD/RAMDISK, and all other files are stored in HDD), we observe many long-time BLOCKED threads on FsDatasetImpl in DataNode. The following is part of the jstack result:
> {noformat}
> "DataXceiver for client DFSClient_NONMAPREDUCE_-1626037897_1 at /192.168.50.16:48521 [Receiving block BP-1042877462-192.168.50.13-1446173170517:blk_1073779272_40852]" - Thread t@93336
>    java.lang.Thread.State: BLOCKED
> 	at org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetImpl.createRbw(FsDatasetImpl.java:1111)
> 	- waiting to lock <18324c9> (a org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetImpl) owned by "DataXceiver for client DFSClient_NONMAPREDUCE_-1626037897_1 at /192.168.50.16:48520 [Receiving block BP-1042877462-192.168.50.13-1446173170517:blk_1073779271_40851]" t@93335
> 	at org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetImpl.createRbw(FsDatasetImpl.java:113)
> 	at org.apache.hadoop.hdfs.server.datanode.BlockReceiver.<init>(BlockReceiver.java:183)
> 	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:745)
>    Locked ownable synchronizers:
> 	- None
> 	
> "DataXceiver for client DFSClient_NONMAPREDUCE_-1626037897_1 at /192.168.50.16:48520 [Receiving block BP-1042877462-192.168.50.13-1446173170517:blk_1073779271_40851]" - Thread t@93335
>    java.lang.Thread.State: RUNNABLE
> 	at java.io.UnixFileSystem.createFileExclusively(Native Method)
> 	at java.io.File.createNewFile(File.java:1012)
> 	at org.apache.hadoop.hdfs.server.datanode.DatanodeUtil.createTmpFile(DatanodeUtil.java:66)
> 	at org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.BlockPoolSlice.createRbwFile(BlockPoolSlice.java:271)
> 	at org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsVolumeImpl.createRbwFile(FsVolumeImpl.java:286)
> 	at org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetImpl.createRbw(FsDatasetImpl.java:1140)
> 	- locked <18324c9> (a org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetImpl)
> 	at org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetImpl.createRbw(FsDatasetImpl.java:113)
> 	at org.apache.hadoop.hdfs.server.datanode.BlockReceiver.<init>(BlockReceiver.java:183)
> 	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:745)
>    Locked ownable synchronizers:
> 	- None
> {noformat}
> We measured the execution of some operations in FsDatasetImpl during the test. Here following is the result.
> !execution_time.png!
> The operations of finalizeBlock, addBlock and createRbw on HDD in a heavy load take a really long time.
> It means one slow operation of finalizeBlock, addBlock and createRbw in a slow storage can block all the other same operations in the same DataNode, especially in HBase when many wal/flusher/compactor are configured.
> We need a finer grained lock mechanism in a new FsDatasetImpl implementation and users can choose the implementation by configuring "dfs.datanode.fsdataset.factory" in DataNode.
> We can implement the lock by either storage level or block-level.


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