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https://issues.apache.org/jira/browse/HADOOP-1849?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12837958#action_12837958
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Suresh Srinivas commented on HADOOP-1849:
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I think we should document the new parameter for the following reasons:
# Number of handlers is currently documented. The queue size per handler is
closely related to this and should be documented as well. These numbers need
tweaking based on the size of the cluster and the type of load. For example a
cluster with smaller heartbeat period, requires bigger queue with the same
number of handlers. A cluster could also live with longer latency instead of
having to increas the number of handlers.
# Current approach of increasing the number of handlers has a drawback; the
response buffer per handler could take up significantly large heap on
increasing the number of handlers.
That said, to me, more important thing is to have this parameter configurable.
Whether it is documented or not is secondary.
The queue size should be dependent on handler count. As the queue size
increases, to certain extent (based on time spent in lock and the cost of each
request etc.) the system can benefit from more number of threads. Keeping them
as it is done today conveys this more clearly.
> IPC server max queue size should be configurable
> ------------------------------------------------
>
> Key: HADOOP-1849
> URL: https://issues.apache.org/jira/browse/HADOOP-1849
> Project: Hadoop Common
> Issue Type: Improvement
> Components: ipc
> Reporter: Raghu Angadi
> Assignee: Konstantin Shvachko
> Attachments: handlerQueueSizeConfig.patch,
> handlerQueueSizeConfig.patch
>
>
> Currently max queue size for IPC server is set to (100 * handlers). Usually
> when RPC failures are observed (e.g. HADOOP-1763), we increase number of
> handlers and the problem goes away. I think a big part of such a fix is
> increase in max queue size. I think we should make maxQsize per handler
> configurable (with a bigger default than 100). There are other improvements
> also (HADOOP-1841).
> Server keeps reading RPC requests from clients. When the number in-flight
> RPCs is larger than maxQsize, the earliest RPCs are deleted. This is the main
> feedback Server has for the client. I have often heard from users that Hadoop
> doesn't handle bursty traffic.
> Say handler count is 10 (default) and Server can handle 1000 RPCs a sec
> (quite conservative/low for a typical server), it implies that an RPC can
> wait for only for 1 sec before it is dropped. If there 3000 clients and all
> of them send RPCs around the same time (not very rare, with heartbeats etc),
> 2000 will be dropped. In stead of dropping the earliest RPCs, if the server
> delays reading new RPCs, the feedback to clients would be much smoother, I
> will file another jira regd queue management.
> For this jira I propose to make queue size per handler configurable, with a
> larger default (may be 500).
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