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https://issues.apache.org/jira/browse/HADOOP-14138?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15960913#comment-15960913
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Steve Loughran commented on HADOOP-14138:
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It doesn't get special treatment: all the filesystems we bundle within the
hadoop JARs have long had the explicit import: s3n, swift, etc. That way: add
the JAR and there's no need to configure anything new. The dynamic stuff really
went in for third party libs, I recall.
HDFS does different magic. When you create an HdfsConfiguration instance,
hdfs-default is registered as a default resource, hdfs-site as an overlay. It's
why every server-side bit of HDFS code explicitly creates instances, and it's
what clients need to do if they want to read in the hdfs defaults. Yarn does
the same; {{AMRMClientImpl}} creates a {{YarnConfiguration}} instance to force
in all its stuff. I do not want to replicate such ugliness elsewhere.
bq. I'm worried that we're introducing a new dependency on core-default by
making this change, while I think we should be going in the opposite direction
and getting rid of dependencies on these files.
You start ignoring core-default and core-site, you stop picking up site
kerberos options, whether UGI should init, etc, etc, and at that point I don't
think things will work. I don't think people should be doing that.
> Remove S3A ref from META-INF service discovery, rely on existing core-default
> entry
> -----------------------------------------------------------------------------------
>
> Key: HADOOP-14138
> URL: https://issues.apache.org/jira/browse/HADOOP-14138
> Project: Hadoop Common
> Issue Type: Sub-task
> Components: fs/s3
> Affects Versions: 2.9.0
> Reporter: Steve Loughran
> Assignee: Steve Loughran
> Priority: Critical
> Fix For: 2.8.0, 2.7.4, 3.0.0-alpha3
>
> Attachments: HADOOP-14138.001.patch, HADOOP-14138-branch-2-001.patch
>
>
> As discussed in HADOOP-14132, the shaded AWS library is killing performance
> starting all hadoop operations, due to classloading on FS service discovery.
> This is despite the fact that there is an entry for fs.s3a.impl in
> core-default.xml, *we don't need service discovery here*
> Proposed:
> # cut the entry from
> {{/hadoop-aws/src/main/resources/META-INF/services/org.apache.hadoop.fs.FileSystem}}
> # when HADOOP-14132 is in, move to that, including declaring an XML file
> exclusively for s3a entries
> I want this one in first as its a major performance regression, and one we
> coula actually backport to 2.7.x, just to improve load time slightly there too
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