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