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From "Suresh Srinivas (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-9150) Unnecessary DNS resolution attempts for logical URIs
Date Wed, 23 Jan 2013 03:20:15 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-9150?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13560358#comment-13560358
] 

Suresh Srinivas commented on HADOOP-9150:
-----------------------------------------

Looking at the patch, FileSystem has two methods that can be overridden. getCanonicalUri()
and canonicalizeUri(). Overriding the first method would be sufficient. Is the reason for
introducing the second method just to reduce the code or getCanonicalUri() should become final
and no longer overridable?
                
> 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, performance, viewfs
>    Affects Versions: 3.0.0, 2.0.2-alpha
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>            Priority: Critical
>         Attachments: hadoop-9150.txt, hadoop-9150.txt, hadoop-9150.txt, hadoop-9150.txt,
hadoop-9150.txt, hadoop-9150.txt, hadoop-9150.txt, 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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