[jira] Commented: (HADOOP-2870) Datanode.shutdown() and Namenode.stop() should close all rpc connections

["Hairong Kuang (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HADOOP-2870?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12575203#action_12575203 ] 

Hairong Kuang commented on HADOOP-2870:
---------------------------------------

Now I understand the reason that each IPC client allows connections to multiple servers. This is for supporting parallel calls in the IPC Client. Parallel calls allow multiple requests to different servers simultaneously.

So I do not plan to change the caching structure.  In this jira, I will add a reference counter to each entry in the IPC client cache. Only when the reference counter becomes zero, a client will be closed. I will also add a static method to the RPC class, stopProxy(VersionProtocol), which supports the close of a proxy, which in turn closes a IPC client when its reference counter becomes zero.

> Datanode.shutdown() and Namenode.stop() should close all rpc connections
> ------------------------------------------------------------------------
>
>                 Key: HADOOP-2870
>                 URL: https://issues.apache.org/jira/browse/HADOOP-2870
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: dfs
>    Affects Versions: 0.16.0
>            Reporter: Hairong Kuang
>            Assignee: Hairong Kuang
>             Fix For: 0.17.0
>
>
> Currently this two cleanup methods do not close all existing rpc connections. If a mini dfs cluster gets shutdown and then restarted as we do in TestFileCreation, RPCs in second mini cluster reuse the unclosed connections opened in the first run but there is no server running to serve the request. So the client get stuck waiting for the response forever if client side timeout gets removed as suggested by hadoop-2811.

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