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https://issues.apache.org/jira/browse/HDFS-7314?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14202971#comment-14202971
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Colin Patrick McCabe commented on HDFS-7314:
--------------------------------------------
bq. It turns out a new bug not related to this was discovered by this change.
If DataStreamer thread exit and closes the stream before application closes the
stream, DFSClient will keep renewing the lease. That is because DataStreamer's
closeInternal marks the stream closed but didn't call DFSClient's endFileLease.
Later when application closes the stream, it will skip DFSClient's endFileLease
given the stream has been closed.
You're right that there is a bug here. There is a lot of discussion about what
to do about this issue in HDFS-4504. It's not as simple as just calling
{{endFileLease}}... if we missed calling {{completeFile}}, the NN will continue
to think that we have a lease open on this file. I think we should avoid
modifying {{DFSOutputStream#close}} here. We should try to keep this JIRA
focused on just the description. Plus HDFS-4504 is a complex issue, not easy
to solve.
{{TestDFSClientRetries.java}}: let's get rid of the unnecessary whitespace
change in the current patch.
I like the idea of getting rid of the {{DFSClient#abort}} function.
The patch looks good once these things are removed, should be ready to go soon!
> Aborted DFSClient's impact on long running service like YARN
> ------------------------------------------------------------
>
> Key: HDFS-7314
> URL: https://issues.apache.org/jira/browse/HDFS-7314
> Project: Hadoop HDFS
> Issue Type: Improvement
> Reporter: Ming Ma
> Assignee: Ming Ma
> Attachments: HDFS-7314-2.patch, HDFS-7314-3.patch, HDFS-7314-4.patch,
> HDFS-7314.patch
>
>
> It happened in YARN nodemanger scenario. But it could happen to any long
> running service that use cached instance of DistrbutedFileSystem.
> 1. Active NN is under heavy load. So it became unavailable for 10 minutes;
> any DFSClient request will get ConnectTimeoutException.
> 2. YARN nodemanager use DFSClient for certain write operation such as log
> aggregator or shared cache in YARN-1492. DFSClient used by YARN NM's
> renewLease RPC got ConnectTimeoutException.
> {noformat}
> 2014-10-29 01:36:19,559 WARN org.apache.hadoop.hdfs.LeaseRenewer: Failed to
> renew lease for [DFSClient_NONMAPREDUCE_-550838118_1] for 372 seconds.
> Aborting ...
> {noformat}
> 3. After DFSClient is in Aborted state, YARN NM can't use that cached
> instance of DistributedFileSystem.
> {noformat}
> 2014-10-29 20:26:23,991 INFO
> org.apache.hadoop.yarn.server.nodemanager.containermanager.localizer.ResourceLocalizationService:
> Failed to download rsrc...
> java.io.IOException: Filesystem closed
> at org.apache.hadoop.hdfs.DFSClient.checkOpen(DFSClient.java:727)
> at org.apache.hadoop.hdfs.DFSClient.getFileInfo(DFSClient.java:1780)
> at
> org.apache.hadoop.hdfs.DistributedFileSystem$17.doCall(DistributedFileSystem.java:1124)
> at
> org.apache.hadoop.hdfs.DistributedFileSystem$17.doCall(DistributedFileSystem.java:1120)
> at
> org.apache.hadoop.fs.FileSystemLinkResolver.resolve(FileSystemLinkResolver.java:81)
> at
> org.apache.hadoop.hdfs.DistributedFileSystem.getFileStatus(DistributedFileSystem.java:1120)
> at org.apache.hadoop.yarn.util.FSDownload.copy(FSDownload.java:237)
> at org.apache.hadoop.yarn.util.FSDownload.call(FSDownload.java:340)
> at org.apache.hadoop.yarn.util.FSDownload.call(FSDownload.java:57)
> at java.util.concurrent.FutureTask.run(FutureTask.java:262)
> at
> java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
> at java.util.concurrent.FutureTask.run(FutureTask.java:262)
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
> at java.lang.Thread.run(Thread.java:745)
> {noformat}
> We can make YARN or DFSClient more tolerant to temporary NN unavailability.
> Given the callstack is YARN -> DistributedFileSystem -> DFSClient, this can
> be addressed at different layers.
> * YARN closes the DistributedFileSystem object when it receives some well
> defined exception. Then the next HDFS call will create a new instance of
> DistributedFileSystem. We have to fix all the places in YARN. Plus other HDFS
> applications need to address this as well.
> * DistributedFileSystem detects Aborted DFSClient and create a new instance
> of DFSClient. We will need to fix all the places DistributedFileSystem calls
> DFSClient.
> * After DFSClient gets into Aborted state, it doesn't have to reject all
> requests , instead it can retry. If NN is available again it can transition
> to healthy state.
> Comments?
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