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https://issues.apache.org/jira/browse/HADOOP-9150?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13534177#comment-13534177
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Todd Lipcon commented on HADOOP-9150:
-------------------------------------
Can think of a few options here:
First option: have DistributedFileSystem override getCanonicalUri, and check if
the URI is a logical one (using {{HAUtil.isLogicalUri}}). If so, don't call
through to canonicalizing the hostname
Or, since I think this also affects viewfs and other filesystems which don't
strictly use hostnames (eg s3n://bucketname/), we can add an overridable
{{isLogicalUri()}} in the FileSystem interface itself, and then have the
affected filesystems return true as necessary.
> 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: ha
> 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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