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https://issues.apache.org/jira/browse/HDFS-6967?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14127125#comment-14127125
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Daryn Sharp commented on HDFS-6967:
-----------------------------------
Ok, I'll clean up the internal patch and post a patch soon. The heap dump
showed a lot of pending jetty connection objects and their associated objects
and most importantly pre-allocated buffers. Limiting the number of connections
is fine for preventing this bloat, but it can prevent webhdfs access to files
that can otherwise be accessed via a lightweight streamer from another node on
the rack.
> DNs may OOM under high webhdfs load
> -----------------------------------
>
> Key: HDFS-6967
> URL: https://issues.apache.org/jira/browse/HDFS-6967
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: datanode, webhdfs
> Affects Versions: 2.0.0-alpha, 3.0.0
> Reporter: Daryn Sharp
> Assignee: Eric Payne
>
> Webhdfs uses jetty. The size of the request thread pool is limited, but
> jetty will accept and queue infinite connections. Every queued connection is
> "heavy" with buffers, etc. Unlike data streamer connections, thousands of
> webhdfs connections will quickly OOM a DN. The accepted requests must be
> bounded and excess clients rejected so they retry on a new DN.
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