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From "Eli Collins (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-3876) NN should not RPC to self to find trash defaults (causes deadlock)
Date Wed, 05 Sep 2012 16:33:09 GMT

     [ https://issues.apache.org/jira/browse/HDFS-3876?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Eli Collins updated HDFS-3876:
------------------------------

    Attachment: hdfs-3876.txt

#1 Done (and the test now just checks if the file was trashed since we can't get the mutated
conf)
#2 Yup, I actually filed HADOOP-8690 for this a month ago. Throws an IOE now.
#3 Only if the server conf is set, and in that case the client conf is overridden, I fixed
the test so the client conf is explicitly disabled if !clientTrash.
                
> NN should not RPC to self to find trash defaults (causes deadlock)
> ------------------------------------------------------------------
>
>                 Key: HDFS-3876
>                 URL: https://issues.apache.org/jira/browse/HDFS-3876
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: name-node
>    Affects Versions: 2.2.0-alpha
>            Reporter: Todd Lipcon
>            Assignee: Eli Collins
>            Priority: Blocker
>         Attachments: hdfs-3876.txt, hdfs-3876.txt, hdfs-3876.txt, hdfs-3876.txt
>
>
> When transitioning a SBN to active, I ran into the following situation:
> - the TrashPolicy first gets loaded by an IPC Server Handler thread. The {{initialize}}
function then tries to make an RPC to the same node to find out the defaults.
> - This is happening inside the NN write lock (since it's part of the active initialization).
Hence, all of the other handler threads are already blocked waiting to get the NN lock.
> - Since no handler threads are free, the RPC blocks forever and the NN never enters active
state.
> We need to have a general policy that the NN should never make RPCs to itself for any
reason, due to potential for deadlocks like this.

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