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https://issues.apache.org/jira/browse/HADOOP-2910?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12579971#action_12579971
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Raghu Angadi commented on HADOOP-2910:
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> Ok, to avoid busy waiting, the listener checks if the call queue is full or
> not before it calls select. It waits if the queue is full. How does this
> sound?
+1. This is much simpler than fiddling with the keys.
One minor improvement we could have now or in future is to make the selector
thread wait for a low water mark (say 90% of max call queue), when it decides
to wait for call queue to be drained. this would reduce number of selector
loops when the queue is hovering at max.
> I think it is ok to accept new connections when the queue is full.
Not selecting as you suggested will stop accepting new connections, which I
think is good. It will fail clients only in extreme cases (ie queue stays full
for many minutes).. in such cases, I guess
> 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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