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From "Alejandro Abdelnur (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-9150) Unnecessary DNS resolution attempts for logical URIs
Date Tue, 18 Dec 2012 14:30:14 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-9150?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13534917#comment-13534917
] 

Alejandro Abdelnur commented on HADOOP-9150:
--------------------------------------------

I'd assume this would impact not only FileSystems but MR/YARN as well. Wouldn't make sense,
similar to what we do for UID-name caching, implement a short-lived NAME-IP caching in NetUtils.
                
> Unnecessary DNS resolution attempts for logical URIs
> ----------------------------------------------------
>
>                 Key: HADOOP-9150
>                 URL: https://issues.apache.org/jira/browse/HADOOP-9150
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: fs/s3, ha, viewfs
>    Affects Versions: 3.0.0, 2.0.2-alpha
>            Reporter: Todd Lipcon
>            Priority: Critical
>         Attachments: log.txt, tracing-resolver.tgz
>
>
> In the FileSystem code, we accidentally try to DNS-resolve the logical name before it
is converted to an actual domain name. In some DNS setups, this can cause a big slowdown -
eg in one misconfigured cluster we saw a 2-3x drop in terasort throughput, since every task
wasted a lot of time waiting for slow "not found" responses from DNS.

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