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Date: Mon, 7 May 2012 17:50:49 +0000 (UTC)
From: "Tsz Wo (Nicholas), SZE (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
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Subject: [jira] [Commented] (HDFS-3376) DFSClient fails to make connection
 to DN if there are many unusable cached sockets
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    [ https://issues.apache.org/jira/browse/HDFS-3376?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13269816#comment-13269816 ] 

Tsz Wo (Nicholas), SZE commented on HDFS-3376:
----------------------------------------------

{code}
+      // Don't use the cache on the last attempt - it's possible that there
+      // are arbitrarily many unusable sockets in the cache, but we don't
+      // want to fail the read.
{code}
Just a question: Will the unusable sockets be closed and removed from the cache?

                
> DFSClient fails to make connection to DN if there are many unusable cached sockets
> ----------------------------------------------------------------------------------
>
>                 Key: HDFS-3376
>                 URL: https://issues.apache.org/jira/browse/HDFS-3376
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: hdfs client
>    Affects Versions: 2.0.0
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>            Priority: Critical
>             Fix For: 2.0.0
>
>         Attachments: hdfs-3376.txt
>
>
> After fixing the datanode side of keepalive to properly disconnect stale clients, (HDFS-3357), the client side has the following issue: when it connects to a DN, it first tries to use cached sockets, and will try a configurable number of sockets from the cache. If there are more cached sockets than the configured number of retries, and all of them have been closed by the datanode side, then the client will throw an exception and mark the replica node as dead.

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