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From "Raghu Angadi (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-2910) Throttle IPC Client/Server during bursts of requests or server slowdown
Date Tue, 15 Apr 2008 02:33:05 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-2910?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12588879#action_12588879
] 

Raghu Angadi commented on HADOOP-2910:
--------------------------------------

- Why do we want exponential backoff? Short timeout in the proposal was intentional. For e.g.,
if the server is too busy for 2 minutes, it would better if client connects in 2min 15sec
rather than 4 minutes. I don't think we really need to throttle SYN packets.

- Do we want the overall timeout to be just 10 min? Note that original patch (callQueue3.patch)
removed the timeout for connect() (may be with the intention of waiting for as long as necessary).

> 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: 0.18.0
>
>         Attachments: callQueue.patch, callQueue1.patch, callQueue2.patch, callQueue3.patch,
TestBacklog.java, TestBacklog.java, TestBacklogWithPool.java, throttleClient.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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