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From "Colin Patrick McCabe (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-7996) After swapping a volume, BlockReceiver reports ReplicaNotFoundException
Date Mon, 30 Mar 2015 21:42:53 GMT

    [ https://issues.apache.org/jira/browse/HDFS-7996?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14387466#comment-14387466

Colin Patrick McCabe commented on HDFS-7996:

The {{BlockReceiver}} should either be closed, or not closed.  Having lots of subtly different
close functions just makes it hard to think about.

It would be much better to add a function like {{BlockReceiver#claimReplicaHandler}} and have
that function return {{BlockReceiver#replicaHandler}} (and set {{BlockReceiver#replicaHandler}}
to null).  Then {{finalizeBlock}} can hold on to the {{replicaHandler}} and its associated
volume for as long as it wants.

I also notice and existing bug in {{BlockReceiver#close}}... if there is an {{IOException}}
closing the data or metadata streams, the volume reference will never be removed.  We should
fix this with a finally block.  Similarly, if there is an IOE closing one stream, we should
try to close the other stream rather than giving up.  Otherwise we have a file descriptor
leak on IO error.

> After swapping a volume, BlockReceiver reports ReplicaNotFoundException
> -----------------------------------------------------------------------
>                 Key: HDFS-7996
>                 URL: https://issues.apache.org/jira/browse/HDFS-7996
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: datanode
>    Affects Versions: 2.6.0
>            Reporter: Lei (Eddy) Xu
>            Assignee: Lei (Eddy) Xu
>            Priority: Critical
>         Attachments: HDFS-7996.000.patch, HDFS-7996.001.patch
> When removing a disk from an actively writing DataNode, the BlockReceiver working on
the disk throws {{ReplicaNotFoundException}} because the replicas are removed from the memory:
> {code}
> 2015-03-26 08:02:43,154 INFO org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetImpl:
Removed volume: /data/2/dfs/dn/current
> 2015-03-26 08:02:43,163 INFO org.apache.hadoop.hdfs.server.common.Storage: Removing block
level storage: /data/2/dfs/dn/current/BP-51301509-
> 2015-03-26 08:02:43,163 WARN org.apache.hadoop.hdfs.server.datanode.DataNode: IOException
in BlockReceiver.run():
> org.apache.hadoop.hdfs.server.datanode.ReplicaNotFoundException: Cannot append to a non-existent
replica BP-51301509-
>         at org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetImpl.getReplicaInfo(FsDatasetImpl.java:615)
>         at org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetImpl.finalizeBlock(FsDatasetImpl.java:1362)
>         at org.apache.hadoop.hdfs.server.datanode.BlockReceiver$PacketResponder.finalizeBlock(BlockReceiver.java:1281)
>         at org.apache.hadoop.hdfs.server.datanode.BlockReceiver$PacketResponder.run(BlockReceiver.java:1241)
>         at java.lang.Thread.run(Thread.java:745)
> {code}
> {{FsVolumeList#removeVolume}} waits all threads release {{FsVolumeReference}} on the
volume to be removed, however, in {{PacketResponder#finalizeBlock()}}, it calls
> {code}
> private void finalizeBlock(long startTime) throws IOException {
>       BlockReceiver.this.close();
>       final long endTime = ClientTraceLog.isInfoEnabled() ? System.nanoTime()
>           : 0;
>       block.setNumBytes(replicaInfo.getNumBytes());
>       datanode.data.finalizeBlock(block);
> {code}
> The {{FsVolumeReference}} was released in {{BlockReceiver.this.close()}} before calling

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