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From "Doug Cutting (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3822) Create a public scheduler API
Date Thu, 31 Jul 2008 16:20:31 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3822?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12618745#action_12618745

Doug Cutting commented on HADOOP-3822:

The line we've drawn to date has been that, if it's in the released javadoc, back-compatibility
requirements apply.  (We promise to deprecate features for one major release before removing
them.  This is in fact the defining characteristic of a major release.  See http://wiki.apache.org/hadoop/Roadmap
for details.)

Currently, the plan is not to release javadoc for the mapreduce and hdfs daemon code packages.
 The scheduler is part of the daemon code, so it's already out of scope for back-compatibility.
 So, for now, this is not an issue.  It will only become an issue if we intend to start including
javadoc for the scheduler in releases.

Longer-term we might wish to have a finer-grained line.  I still believe it ought to be easy
to determine from the javadoc whether something is a supported API.  So, if we were to, e.g.,
start releasing Scheduler javadoc, we'd need to make sure that unstable methods were clearly
marked.  In Lucene we adopted the convention of adding an "Expert:" to the beginning of javadoc
comments for APIs that most users should ignore.  Similarly, we might add something like "Unstable:"
to APIs that we expect will change.

Would an @Internal tag be able to affect the javadoc?

> Create a public scheduler API
> -----------------------------
>                 Key: HADOOP-3822
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3822
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: mapred
>            Reporter: Tom White
>             Fix For: 0.19.0
>         Attachments: hadoop-3822.patch, hadoop-3822.sh
> The work in HADOOP-3412 provided an API to support pluggable schedulers. However implementations
have to be in the org.apache.hadoop.mapred package, which is undesirable. The goal of this
issue is to create a public API for scheduler writers to code against.

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