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Date: Tue, 24 Nov 2015 21:00:12 +0000 (UTC)
From: "Xiaoyu Yao (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Message-ID: <JIRA.12851465.1438713009000.181894.1448398812612@Atlassian.JIRA>
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Subject: [jira] [Updated] (HDFS-8855) Webhdfs client leaks active NameNode
 connections
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     [ https://issues.apache.org/jira/browse/HDFS-8855?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Xiaoyu Yao updated HDFS-8855:
-----------------------------
      Resolution: Fixed
    Hadoop Flags: Reviewed
          Status: Resolved  (was: Patch Available)

Thanks [~xiaobingo]  and [~cnauroth] for the contribution and all for the reviews. I've committed the patch to trunk and branch-2.

> Webhdfs client leaks active NameNode connections
> ------------------------------------------------
>
>                 Key: HDFS-8855
>                 URL: https://issues.apache.org/jira/browse/HDFS-8855
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: webhdfs
>            Reporter: Bob Hansen
>            Assignee: Xiaobing Zhou
>             Fix For: 2.8.0
>
>         Attachments: HDFS-8855.005.patch, HDFS-8855.006.patch, HDFS-8855.007.patch, HDFS-8855.008.patch, HDFS-8855.009.patch, HDFS-8855.1.patch, HDFS-8855.2.patch, HDFS-8855.3.patch, HDFS-8855.4.patch, HDFS_8855.prototype.patch
>
>
> The attached script simulates a process opening ~50 files via webhdfs and performing random reads.  Note that there are at most 50 concurrent reads, and all webhdfs sessions are kept open.  Each read is ~64k at a random position.  
> The script periodically (once per second) shells into the NameNode and produces a summary of the socket states.  For my test cluster with 5 nodes, it took ~30 seconds for the NameNode to have ~25000 active connections and fails.
> It appears that each request to the webhdfs client is opening a new connection to the NameNode and keeping it open after the request is complete.  If the process continues to run, eventually (~30-60 seconds), all of the open connections are closed and the NameNode recovers.  
> This smells like SoftReference reaping.  Are we using SoftReferences in the webhdfs client to cache NameNode connections but never re-using them?


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