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https://issues.apache.org/jira/browse/BIGTOP-1689?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14360285#comment-14360285
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Michael Weiser commented on BIGTOP-1689:
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http://hadoop.apache.org/docs/r2.4.1/api/org/apache/hadoop/conf/Configuration.html
is the only documentation on how the configuration files work I can find. It
explains how the resource search paths and final parameters work. Nothing is
said about order within one file.
A quick test with two settings in hdfs-site.xml shows that duplicate settings
do not cause a parse error. The last value wins. If the first occurence is
marked final, its value wins and the logfile correctly shows an attempt to
overwrite a final value. So at least empirically all seems well with overriding
values within the same file.
> puppet: Allow merging arbitrary site configuration
> --------------------------------------------------
>
> Key: BIGTOP-1689
> URL: https://issues.apache.org/jira/browse/BIGTOP-1689
> Project: Bigtop
> Issue Type: Improvement
> Components: deployment
> Affects Versions: 0.8.0
> Reporter: Peter Slawski
> Assignee: Peter Slawski
> Fix For: 0.9.0
>
> Attachments: BIGTOP-1689.1.patch
>
>
> Puppet should be flexible in allowing arbitrary configuration name value
> pairs to be merged into a given site.xml file that was generated from a
> template.
> For example, the following could be included in site.yaml which would add a
> configuration entry for hadoop.tmp.dir in core-site.xml:
> {code}
> hadoop::common_hdfs::hadoop_core_site_overrides:
> "hadoop.tmp.dir": "/mnt/var/lib/hadoop/tmp"
> {code}
> This could be implemented as a puppet custom-function taking in the output of
> template:
> {code}
> file {
> "/etc/hadoop/conf/core-site.xml":
> content => merge_site(template('hadoop/core-site.xml'),
> $hadoop_core_site_overrides)
> require => [Package["hadoop"]],
> }
> {code}
> Perhaps another approach would be to have site.xml templates be created from
> a single map of name value pairs. The merge would happen before the file
> content is generated from the template.
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