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https://issues.apache.org/jira/browse/HADOOP-1849?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12834390#action_12834390
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Konstantin Shvachko commented on HADOOP-1849:
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I intentionally did not put it into any of *-dafult.xml files. I think it
should be an undocumented parameter to prevent people from changing it
unknowingly. There are two main reasons for that:
# we still don't know what is the reasonable default value
# the optimal rpc queue size may be different for different applications. HDFS
may work better with one size and MR may need another size. So the parameter
will have different values in hdfs-site.xml and mapred-site.xml. Placing the
parameter in core-default.xml makes it somewhat confusing.
> 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
> Fix For: 0.20.2
>
> Attachments: 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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