hadoop-hdfs-issues mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Colin Patrick McCabe (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (HDFS-7060) Contentions of the monitor of FsDatasetImpl block DN's heartbeat
Date Wed, 01 Apr 2015 21:31:54 GMT

    [ https://issues.apache.org/jira/browse/HDFS-7060?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14391501#comment-14391501
] 

Colin Patrick McCabe edited comment on HDFS-7060 at 4/1/15 9:31 PM:
--------------------------------------------------------------------

While I agree that making the DataNode heartbeat lockless might be a good idea in theory,
it is not a bugfix.  It is an optimization or improvement.

In contrast, the issue with {{FsDatasetImpl#createTemporary}} holding the lock for a long
period is a bug, and it needs to be fixed.  Even if the heartbeat is made lockless, HDFS-7999
will still cause many problems such as extremely high write and read latency, unresponsive
datanodes, and so on.  Making the heartbeat lockless does not fix HDFS-7999, although it might
alleviate a few of the symptoms.

Edit: I see that Haohui explained why we might be able to remove some of these locks.  I'll
try to take a look later


was (Author: cmccabe):
While I agree that making the DataNode heartbeat lockless might be a good idea in theory,
it is not a bugfix.  It is an optimization or improvement.

In contrast, the issue with {{FsDatasetImpl#createTemporary}} holding the lock for a long
period is a bug, and it needs to be fixed.  Even if the heartbeat is made lockless, HDFS-7999
will still cause many problems such as extremely high write and read latency, unresponsive
datanodes, and so on.  Making the heartbeat lockless does not fix HDFS-7999, although it might
alleviate a few of the symptoms.

The patch here seems to remove a bunch of synchronized blocks, but I don't see any explanation
for how we will avoid race conditions associated with concurrent access that these synchronized
blocks were protecting against.  This needs to be be much better thought-out before we can
consider it.

> Contentions of the monitor of FsDatasetImpl block DN's heartbeat
> ----------------------------------------------------------------
>
>                 Key: HDFS-7060
>                 URL: https://issues.apache.org/jira/browse/HDFS-7060
>             Project: Hadoop HDFS
>          Issue Type: Bug
>            Reporter: Haohui Mai
>            Assignee: Xinwei Qin 
>            Priority: Critical
>         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}



--
This message was sent by Atlassian JIRA
(v6.3.4#6332)

Mime
View raw message