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From "Xiao Chen (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-9781) FsDatasetImpl#getBlockReports can occasionally throw NullPointerException
Date Fri, 12 Feb 2016 21:56:18 GMT

     [ https://issues.apache.org/jira/browse/HDFS-9781?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Xiao Chen updated HDFS-9781:
    Attachment: HDFS-9781.01.patch

Thanks for creating this [~jojochuang].

The 'A failed test' link is no longer valid. :( But I've managed to reproduce this in about
1% frequency. I think there're 2 problems here:
# Test timeout without obvious information (so that people have to see the code to know why
it timed out).

Patch 1 is attached to address them:
# Adds more information to the test, and also waits for BR to be received before releasing
the reference. BTW, the test doesn't care whether a exception is thrown, so IMO no {{assertExceptionContains}}
is needed.
# This is from the changes in HDFS-9701: during {{wait}}, the thread is put on hold and other
thread may proceed (getBlockReport, in this case). Since the {{volumeMap}} is not yet cleared
it's possible for the BR thread to get a null volume. Eddy and I discussed this in HDFS-9701,
but at that time I was using {{Thread.sleep}} which holds the lock. A later findbugs warning
made me to switch to {{wait}} (which IMO is the right thing to do), but then the sequence
should've be modified to make sure internal states such as {{volumeMap}} is safe.

[~eddyxu], could you please review? Thanks.

> FsDatasetImpl#getBlockReports can occasionally throw NullPointerException
> -------------------------------------------------------------------------
>                 Key: HDFS-9781
>                 URL: https://issues.apache.org/jira/browse/HDFS-9781
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: datanode
>    Affects Versions: 3.0.0
>         Environment: Jenkins
>            Reporter: Wei-Chiu Chuang
>            Assignee: Wei-Chiu Chuang
>         Attachments: HDFS-9781.01.patch
> FsDatasetImpl#getBlockReports occasionally throws NPE. The NPE caused TestFsDatasetImpl#testRemoveVolumeBeingWritten
to time out, because the test waits for the call to FsDatasetImpl#getBlockReports to complete
without exceptions.
> Additionally, the test should be updated to identify an expected exception, using {{GenericTestUtils.assertExceptionContains()}}
> {noformat}
> Exception in thread "Thread-20" java.lang.NullPointerException
>         at org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetImpl.getBlockReports(FsDatasetImpl.java:1709)
>         at org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.TestFsDatasetImpl$1BlockReportThread.run(TestFsDatasetImpl.java:587)
> 2016-02-08 15:47:30,379 [Thread-21] WARN  impl.TestFsDatasetImpl (TestFsDatasetImpl.java:run(606))
- Exception caught. This should not affect the test
> java.io.IOException: Failed to move meta file for ReplicaBeingWritten, blk_0_0, RBW
>   getNumBytes()     = 0
>   getBytesOnDisk()  = 0
>   getVisibleLength()= 0
>   getVolume()       = /home/weichiu/hadoop/hadoop-hdfs-project/hadoop-hdfs/target/test/data/Nmi6rYndvr/data0/current
>   getBlockFile()    = /home/weichiu/hadoop/hadoop-hdfs-project/hadoop-hdfs/target/test/data/Nmi6rYndvr/data0/current/bpid-0/current/rbw/blk_0
>   bytesAcked=0
>   bytesOnDisk=0 from /home/weichiu/hadoop/hadoop-hdfs-project/hadoop-hdfs/target/test/data/Nmi6rYndvr/data0/current/bpid-0/current/rbw/blk_0_0.meta
to /home/weichiu/hadoop/hadoop-hdfs-project/hadoop-hdfs/target/test/data/Nmi6rYndvr/data0/current/bpid-0/current/finalized/subdir0/subdir0/blk_0_0.meta
>         at org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetImpl.moveBlockFiles(FsDatasetImpl.java:857)
>         at org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.BlockPoolSlice.addFinalizedBlock(BlockPoolSlice.java:295)
>         at org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsVolumeImpl.addFinalizedBlock(FsVolumeImpl.java:819)
>         at org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetImpl.finalizeReplica(FsDatasetImpl.java:1620)
>         at org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetImpl.finalizeBlock(FsDatasetImpl.java:1601)
>         at org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.TestFsDatasetImpl$1ResponderThread.run(TestFsDatasetImpl.java:603)
> Caused by: java.io.IOException: renameTo(src=/home/weichiu/hadoop/hadoop-hdfs-project/hadoop-hdfs/target/test/data/Nmi6rYndvr/data0/current/bpid-0/current/rbw/blk_0_0.meta,
>         at org.apache.hadoop.io.nativeio.NativeIO.renameTo(NativeIO.java:873)
>         at org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetImpl.moveBlockFiles(FsDatasetImpl.java:855)
>         ... 5 more
> 2016-02-08 15:47:34,381 [Thread-19] INFO  impl.FsDatasetImpl (FsVolumeList.java:waitVolumeRemoved(287))
- Volume reference is released.
> 2016-02-08 15:47:34,384 [Thread-19] INFO  impl.TestFsDatasetImpl (TestFsDatasetImpl.java:testRemoveVolumeBeingWritten(622))
- Volumes removed
> {noformat}

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