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https://issues.apache.org/jira/browse/HADOOP-9150?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13534396#comment-13534396
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Aaron T. Myers commented on HADOOP-9150:
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bq. 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.
This one makes sense to me, given that this affects more than just HDFS proper.
> 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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