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From "Denes Arvay (JIRA)" <j...@apache.org>
Subject [jira] [Created] (FLUME-2973) Deadlock in hdfs sink
Date Wed, 17 Aug 2016 13:38:20 GMT
Denes Arvay created FLUME-2973:

             Summary: Deadlock in hdfs sink
                 Key: FLUME-2973
                 URL: https://issues.apache.org/jira/browse/FLUME-2973
             Project: Flume
          Issue Type: Bug
          Components: Sinks+Sources
    Affects Versions: v1.7.0
            Reporter: Denes Arvay
            Assignee: Denes Arvay
            Priority: Critical

Automatic close of BucketWriters (when open file count reached {{hdfs.maxOpenFiles}}) and
the file rolling thread can end up in deadlock.

When creating a new {{BucketWriter}} in {{HDFSEventSink}} it locks {{HDFSEventSink.sfWritersLock}}
and the {{close()}} called in {{HDFSEventSink.sfWritersLock.removeEldestEntry}} tries to lock
the {{BucketWriter}} instance.
On the other hand if the file is being rolled in {{BucketWriter.close(boolean)}} it locks
the {{BucketWriter}} instance first and in the close callback it tries to lock the {{sfWritersLock}}.

The chances for this deadlock is higher when the {{hdfs.maxOpenFiles}}'s value is low (1).

Script to reproduce: https://gist.github.com/adenes/96503a6e737f9604ab3ee9397a5809ff
(put to {{flume-ng-sinks/flume-hdfs-sink/src/main/java/org/apache/flume/sink/hdfs}})
Deadlock usually occurs before ~30 iterations.

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