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From "Wei-Chiu Chuang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-14048) DFSOutputStream close() throws exception on subsequent call after DataNode restart
Date Tue, 06 Nov 2018 15:23:00 GMT

    [ https://issues.apache.org/jira/browse/HDFS-14048?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16676889#comment-16676889
] 

Wei-Chiu Chuang commented on HDFS-14048:
----------------------------------------

+1

> DFSOutputStream close() throws exception on subsequent call after DataNode restart
> ----------------------------------------------------------------------------------
>
>                 Key: HDFS-14048
>                 URL: https://issues.apache.org/jira/browse/HDFS-14048
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: hdfs-client
>    Affects Versions: 2.3.0
>            Reporter: Erik Krogen
>            Assignee: Erik Krogen
>            Priority: Major
>         Attachments: HDFS-14048.000.patch
>
>
> We recently discovered an issue in which, during a rolling upgrade, some jobs were failing
with exceptions like (sadly this is the whole stack trace):
> {code}
> java.io.IOException: A datanode is restarting: DatanodeInfoWithStorage[1.1.1.1:71,BP-XXXX,DISK]
> 	at org.apache.hadoop.hdfs.DFSOutputStream$DataStreamer$ResponseProcessor.run(DFSOutputStream.java:877)
> {code}
> with an earlier statement in the log like:
> {code}
> INFO [main] org.apache.hadoop.hdfs.DFSClient: A datanode is restarting: DatanodeInfoWithStorage[1.1.1.1:71,BP-XXXX,DISK]
> {code}
> Strangely we did not see any other logs about the {{DFSOutputStream}} failing after waiting
for the DataNode restart. We eventually realized that in some cases {{DFSOutputStream#close()}}
may be called more than once, and that if so, the {{IOException}} above is thrown on the _second_
call to {{close()}} (this is even with HDFS-5335; prior to this it would have been thrown
on all calls to {{close()}} besides the first).
> The problem is that in {{DataStreamer#createBlockOutputStream()}}, after the new output
stream is created, it resets the error states:
> {code}
>         errorState.resetInternalError();
>         // remove all restarting nodes from failed nodes list
>         failed.removeAll(restartingNodes);
>         restartingNodes.clear(); 
> {code}
> But it forgets to clear {{lastException}}. When {{DFSOutputStream#closeImpl()}} is called
a second time, this block is triggered:
> {code}
>     if (isClosed()) {
>       LOG.debug("Closing an already closed stream. [Stream:{}, streamer:{}]",
>           closed, getStreamer().streamerClosed());
>       try {
>         getStreamer().getLastException().check(true);
> {code}
> The second time, {{isClosed()}} is true, so the exception checking occurs and the "Datanode
is restarting" exception is thrown even though the stream has already been successfully closed.



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