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https://issues.apache.org/jira/browse/HADOOP-15007?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16234337#comment-16234337
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Steve Loughran commented on HADOOP-15007:
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# Is this expected to be a stable change? Or at least: when do we expect it to
be stable?
# What is going to happen when an older version of Hadoop encounters an XML
file with a new field in it?
# we need some tests which actually set out to break the mechanism. Invalid
tags etc.
# Javadocs and end-user docs to cover what can and cannot be done with tags,
how to use. {{Configuration's}} own javadocs are the defacto documentation of
the XML format: they need to be updated with the change.
# what's going to to happen when existing code which serializes/deserializes
configs using Hadoop writables encounters configs with tags? Can an old
hadoop-common lib deserialize, say core-default.xml with tags added? I don't
see any tests for that, and I'm assuming "no" unless it can be demonstrated.
# Can I add tags to a propery retrieved with getPassword()?
# If I overrride a -default property in a file, does it inherit the tags from
the parent?
# If I add tags to an overidden property, do the tags override or replace
existing ones?
# {{Configuration.readTagFromConfig}}. If there's an invalid tag in a -default
file, is it going to fill the log files with info messages on every load of
every single configuration file? If so, it's too noisy. One warning per
(file/property) the way we do for deprecated tags.
# {{Configuration.getPropertyTag}} returns a {{PropertyTag}} enum; which is
marked as Private/Evolving. But configuration is Public/Stable. Either we need
to mark PropertyTag as Public/{Evolving/Unstable} or {{getPropertyTag}} is
marked as Private
# Could there have been a way to allow {{PropertyTag}} enums to be registered
dynamically/via classname strings, so that they can be kept in the specific
modules. We've now tainted hadoop-common with details about yarn, hdfs, ozone.
Right now, I'm not convinced this is a compatible change, and will need to be
convinced that it is before we can ship a version of Hadoop with the feature.
If there are problems, unless they can be addressed we may need to exclude
supporting tags in the core-, hdfs- and yarn- on compatibility grounds.
> Stabilize and document Configuration <tag> element
> --------------------------------------------------
>
> Key: HADOOP-15007
> URL: https://issues.apache.org/jira/browse/HADOOP-15007
> Project: Hadoop Common
> Issue Type: Improvement
> Components: conf
> Affects Versions: 3.1.0
> Reporter: Steve Loughran
> Priority: Blocker
>
> HDFS-12350 (moved to HADOOP-15005). Adds the ability to tag properties with a
> <tag> value.
> We need to make sure that this feature is backwards compatible & usable in
> production. That's docs, testing, marshalling etc.
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