[jira] [Commented] (HDFS-5203) Concurrent clients that add a cache directive on the same path may prematurely uncache from each other.

["Chris Nauroth (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HDFS-5203?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13796994#comment-13796994 ] 

Chris Nauroth commented on HDFS-5203:
-------------------------------------

Now that the big changes in HDFS-5096 are winding down, I'm planning on revisiting HDFS-5203 soon and preparing a patch.

> Concurrent clients that add a cache directive on the same path may prematurely uncache from each other.
> -------------------------------------------------------------------------------------------------------
>
>                 Key: HDFS-5203
>                 URL: https://issues.apache.org/jira/browse/HDFS-5203
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: namenode
>    Affects Versions: HDFS-4949
>            Reporter: Chris Nauroth
>            Assignee: Chris Nauroth
>
> When a client adds a cache directive, we assign it a unique ID and return that ID to the client.  If multiple clients add a cache directive for the same path, then we return the same ID.  If one client then removes the cache entry for that ID, then it is removed for all clients.  Then, when this change becomes visible in subsequent cache reports, the datanodes may {{munlock}} the block before the other clients are done with it.



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