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From "Daryn Sharp (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-9150) Unnecessary DNS resolution attempts for logical URIs
Date Wed, 23 Jan 2013 15:44:14 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-9150?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13560759#comment-13560759
] 

Daryn Sharp commented on HADOOP-9150:
-------------------------------------

I'm also kind of leaning towards a final on {{getCanonicalUri()}}.  If someone overrides it
then there would be an inconsistency in calling {{getCanonicalUri()}} and {{getCanonicalUri(getUri())}}.

I think the comparison {{getDefaultPort() != 0}} should be {{getDefaultPort() > 0}} since
-1 signifies no port to URI.  I find it very odd that the default impl returns 0 instead of
-1.  Perhaps that should be changed?  If so, maybe it should be {{getDefaultPort() != -1}}.

Very minor, but I'd consider renaming {{canonicalizeUri(URI)}} to {{getCanonicalUri(URI)}}.
 If you disagree, that's ok.

                
> 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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