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From "Uma Maheswara Rao G (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-6889) Make RPC to have an option to timeout
Date Mon, 11 Jul 2011 09:55:00 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-6889?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13063251#comment-13063251
] 

Uma Maheswara Rao G commented on HADOOP-6889:
---------------------------------------------

Hay Hairong,

 I have seen waitForProxy is passing 0 as rpcTimeOut. It is hardcoded value.

{code}

return waitForProtocolProxy(protocol, clientVersion, addr, conf, 0, connTimeout);

{code}

 If user wants to control this value then , how can he configure?

Here we have a situation, where clients are waiting for long time.HDFS-1880.

I thought, this issue can solve that problem. But how this can be controlled by the user in
Hadoop.


{quote}

I plan to add a new configuration ipc.client.max.pings that specifies the max number of pings
that a client could try. If a response can not be received after the specified max number
of pings, a SocketTimeoutException is thrown. If this configuration property is not set, a
client maintains the current semantics, waiting forever.
{quote}
 We have choosen this implementation for our cluster. 

I am just checking , whether i can use rpcTimeOut itself to control. ( since this change already
committed).

Can you please clarify more?

> Make RPC to have an option to timeout
> -------------------------------------
>
>                 Key: HADOOP-6889
>                 URL: https://issues.apache.org/jira/browse/HADOOP-6889
>             Project: Hadoop Common
>          Issue Type: New Feature
>          Components: ipc
>    Affects Versions: 0.22.0
>            Reporter: Hairong Kuang
>            Assignee: Hairong Kuang
>             Fix For: 0.20-append, 0.22.0
>
>         Attachments: ipcTimeout.patch, ipcTimeout1.patch, ipcTimeout2.patch
>
>
> Currently Hadoop RPC does not timeout when the RPC server is alive. What it currently
does is that a RPC client sends a ping to the server whenever a socket timeout happens. If
the server is still alive, it continues to wait instead of throwing a SocketTimeoutException.
This is to avoid a client to retry when a server is busy and thus making the server even busier.
This works great if the RPC server is NameNode.
> But Hadoop RPC is also used for some of client to DataNode communications, for example,
for getting a replica's length. When a client comes across a problematic DataNode, it gets
stuck and can not switch to a different DataNode. In this case, it would be better that the
client receives a timeout exception.
> I plan to add a new configuration ipc.client.max.pings that specifies the max number
of pings that a client could try. If a response can not be received after the specified max
number of pings, a SocketTimeoutException is thrown. If this configuration property is not
set, a client maintains the current semantics, waiting forever.

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