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From "Raghu Angadi (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3779) limit concurrent connections(data serving thread) in one datanode
Date Fri, 18 Jul 2008 00:23:31 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3779?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12614582#action_12614582

Raghu Angadi commented on HADOOP-3779:

Couple of things :
* HADOOP-2346 has nothing to with number of threads. Its same as before. If anything it makes
it easier to move to using a thread pool.
* After HADOOP-3633, DN limits number simultaneous threads to 256. Is that what you want?
Let us know if that works for you.

> limit concurrent connections(data serving thread) in one datanode
> -----------------------------------------------------------------
>                 Key: HADOOP-3779
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3779
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: dfs
>    Affects Versions: 0.17.1
>            Reporter: LN
>            Priority: Minor
> i'm here after HADOOP-2341 and HADOOP-2346, in my hbase env, many opening mapfiles cause
datanode OOME(stack memory), because 2000+ data serving threads in datanode process.
> although HADOOP-2346 has implements timeouts, it will be some situation many connection
created  before the read timeout(default 6min) reach. like hbase does, it open all files on
regionserver startup. 
> limit concurrent connections(data serving thread) will make datanode more stable. and
i think it could be done in SocketIOWithTimeout$SelectorPool#select:
> 1. in SelectorPool#select, record all waiting SelectorInfo instances in a List at the
beginning, and remove it after 'Selector#select' done.
> 2. before real 'select',  do a limitation check, if reached, close the first selectorInfo.

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