[jira] Commented: (HADOOP-6889) Make RPC to have an option to timeout

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

    [ https://issues.apache.org/jira/browse/HADOOP-6889?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12893833#action_12893833 ] 

Hairong Kuang commented on HADOOP-6889:
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On a second thought, it would be nice if RPC proxies could configure differently. For example, one may want to have timeout on RPCs to DataNodes but no timeout on RPCs to NameNode. So I propose to add an additional parameter, maxRpcWaitingTime, to RPC#getProxy, meaning for every RPC call to this proxy, SocketTimeout is thrown if a client has not received a response in maxRpcWaitingTime. If maxRpcWaitingTime is zero, a RPC call will not timeout.

In this way, a client could configure maxRpcWaitingTime differently for its communicatations to NameNode and DataNodes. 



> 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: 0.22.0, 0.20-append
>
>
> 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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