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From "Raghu Angadi (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-1849) IPC server max queue size should be configurable
Date Tue, 23 Feb 2010 19:26:28 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-1849?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12837399#action_12837399

Raghu Angadi commented on HADOOP-1849:

Current RPC is not that sensitive to this queue size. 

Queue size was very important before RPC improvements in 2008, because it used to rudely drop
the RPCs if the queue was full. But now, RPC server handles full queue and and bursty traffic
quite well.

Did you recently come across a case where adjusting this value improves things? 

Either way, the undocumented config parameter is fine.

> 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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