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https://issues.apache.org/jira/browse/HADOOP-8050?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13206342#comment-13206342
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Luke Lu commented on HADOOP-8050:
---------------------------------
The reason of the deadlock is that the JMX serving thread has different lock
order (source adapter, source (which can be metrics system)) than the snapshot
thread (metrics system, source adapter). The correct fix (sans moving jmx to a
sink) is not removing the lock on metrics system in the snapshot thread but
fixing the lock order in MetricsSourceAdapter (to make source.getMetrics is
done without holding the adapter lock).
> Deadlock in metrics
> -------------------
>
> Key: HADOOP-8050
> URL: https://issues.apache.org/jira/browse/HADOOP-8050
> Project: Hadoop Common
> Issue Type: Bug
> Components: metrics
> Affects Versions: 0.20.204.0, 0.20.205.0, 0.23.0, 1.0.0
> Reporter: Kihwal Lee
> Assignee: Kihwal Lee
> Fix For: 1.1.0, 1.0.1
>
> Attachments: hadoop-8050.patch.txt
>
>
> The metrics serving thread and the periodic snapshot thread can deadlock.
> It happened a few times on one of namenodes we have. When it happens RPC
> works but the web ui and hftp stop working. I haven't look at the trunk too
> closely, but it might happen there too.
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