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https://issues.apache.org/jira/browse/HADOOP-6889?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12893887#action_12893887
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Doug Cutting commented on HADOOP-6889:
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As I recall, RPC calls used to have a timeout that, combined with the retry
proxy, would spiral load on servers. But I think timeouts when retries go to a
different server should not have the same problem.
> 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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