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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-16212) Many connections to datanode are created when doing a large scan
Date Tue, 19 Jul 2016 04:56:20 GMT

    [ https://issues.apache.org/jira/browse/HBASE-16212?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15383580#comment-15383580

stack commented on HBASE-16212:

[~dengzh] Makes sense. Nice one. Let me compare logging how many connections we make. Your
patch should perform much better especially if any locality to the reads.

> Many connections to datanode are created when doing a large scan 
> -----------------------------------------------------------------
>                 Key: HBASE-16212
>                 URL: https://issues.apache.org/jira/browse/HBASE-16212
>             Project: HBase
>          Issue Type: Improvement
>    Affects Versions: 1.1.2
>            Reporter: Zhihua Deng
>         Attachments: HBASE-16212.patch, HBASE-16212.v2.patch, regionserver-dfsinputstream.log
> As described in https://issues.apache.org/jira/browse/HDFS-8659, the datanode is suffering
from logging the same repeatedly. Adding log to DFSInputStream, it outputs as follows:
> 2016-07-10 21:31:42,147 INFO  [B.defaultRpcServer.handler=22,queue=1,port=16020] hdfs.DFSClient:
DFSClient_NONMAPREDUCE_1984924661_1 seek DatanodeInfoWithStorage[,DS-086bc494-d862-470c-86e8-9cb7929985c6,DISK]
for BP-360285305- pos: 111506876, targetPos:
>  ...
> As the pos of this input stream is larger than targetPos(the pos trying to seek), A new
connection to the datanode will be created, the older one will be closed as a consequence.
When the wrong seeking ops are large, the datanode's block scanner info message is spamming
logs, as well as many connections to the same datanode will be created.
> hadoop version: 2.7.1

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