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https://issues.apache.org/jira/browse/HDFS-3876?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13446500#comment-13446500
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Aaron T. Myers commented on HDFS-3876:
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Makes sense. I was just responding to the comment that "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."
> 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: 3.0.0, 2.2.0-alpha
> Reporter: Todd Lipcon
> Assignee: Eli Collins
> Priority: Blocker
> Attachments: 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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