[jira] [Assigned] (HDFS-8855) Webhdfs client leaks active NameNode connections

["Xiaobing Zhou (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HDFS-8855?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Xiaobing Zhou reassigned HDFS-8855:
-----------------------------------

    Assignee: Xiaobing Zhou

> 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
>         Environment: HDP 2.2
>            Reporter: Bob Hansen
>            Assignee: Xiaobing Zhou
>
> 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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