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https://issues.apache.org/jira/browse/HADOOP-2910?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12579668#action_12579668
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Doug Cutting commented on HADOOP-2910:
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On second thought, it won't cause busy-wait, but rather, since the key is
removed from the selector, readAndProcess() won't be called again until more
data arrives for that connection. Instead, the connection should be
re-registered when the callQueue size is back within range. So perhaps we need
a queue of connections that have unread input that we put things into when the
call queue is full, then pop them off later when the queue empties. Of course,
that would defeat the purpose of this patch...
Also, shouldn't we avoid accepting new connections when the queue is full too?
> Throttle IPC Client/Server during bursts of requests or server slowdown
> -----------------------------------------------------------------------
>
> Key: HADOOP-2910
> URL: https://issues.apache.org/jira/browse/HADOOP-2910
> Project: Hadoop Core
> Issue Type: Improvement
> Components: ipc
> Affects Versions: 0.16.0
> Reporter: Hairong Kuang
> Assignee: Hairong Kuang
> Fix For: 0.17.0
>
> Attachments: callQueue.patch
>
>
> I propose the following to avoid an IPC server being swarmed by too many
> requests and connections
> 1. Limit call queue length or limit the amount of memory used in the call
> queue. This can be done by including the size of a request in the header and
> storing unmarshaled requests in the call queue.
> 2. If the call queue is full or queue buffer is full, stop reading requests
> from sockets. So requests stay at the server's system buffer or at the client
> side and thus eventually throttle the client.
> 3. Limit the total number of connections. Do not accept new connections if
> the connection limit is exceeded. (Note: this solution is unfair to new
> connections.)
> 4. If receive out of memory exception, close the current connection.
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