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Doug Cutting commented on HADOOP-6889:
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+1 this patch looks reasonable to me, pending Hudson's scrutiny.
> 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
>
> Attachments: ipcTimeout.patch, ipcTimeout1.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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