[jira] [Updated] (FLUME-2973) Deadlock in hdfs sink

["Yan Jian (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/FLUME-2973?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Yan Jian updated FLUME-2973:
----------------------------
    Attachment: FLUME-2973-1.patch

I made smallest modification ([^FLUME-2973-1.patch]) to escape from inconsistent code format and unrelated code smells in original code.
It just breaks {{circular wait}} condition by reversing the lock sequence in rolling thread, avoiding lock transfer.

Turn to {{trunk}} branch, such classes ({{BucketWriter}}, {{HDFSEventSink}}, etc.) are reformatted, but still contain several code smells.
# Inappropriate naming, such as {{org.apache.flume.sink.hdfs.BucketWriter.closed}}.
# Coupling between classes {{BucketWriter}} and {{HDFSEventSink}}.
# Meaningless duplicate closing of a bucket writer.

IMHO, it is necessary to refactor classes in {{org.apache.flume.sink.hdfs}} package.

> 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
>              Labels: hdfssink
>         Attachments: FLUME-2973-1.patch, FLUME-2973.patch
>
>
> 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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