[jira] [Commented] (HADOOP-7738) Document incompatible API changes between 0.20.20x and 0.23.0 release

["Tom White (Commented) (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HADOOP-7738?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13163731#comment-13163731 ] 

Tom White commented on HADOOP-7738:
-----------------------------------

Here are some notes on the differences I have found so far between the 0.20.x release series and 0.23.0 which break compatibility in some way.

* MAPREDUCE-954 changed some context classes to interfaces (e.g. JobContext, MapContext, TaskAttemptContext, TaskInputOutputContext). This change should not impact user code (since such code doesn't implement these interfaces) although it does mean that user code (including libraries like Pig) will need to be recompiled. See note (1) at http://wiki.eclipse.org/Evolving_Java-based_APIs_2#Evolving_API_packages
* MAPREDUCE-901 changes Counter from a class to an interface. Clients need to recompile.
* HADOOP-6201 changed FileSystem#listStatus to throw FileNotFoundException when the file is not found, rather than returning null. Clients need to review usage of this method and update their code to handle this case. 

                
> Document incompatible API changes between 0.20.20x and 0.23.0 release
> ---------------------------------------------------------------------
>
>                 Key: HADOOP-7738
>                 URL: https://issues.apache.org/jira/browse/HADOOP-7738
>             Project: Hadoop Common
>          Issue Type: Improvement
>            Reporter: Tom White
>            Assignee: Tom White
>            Priority: Blocker
>             Fix For: 0.23.1
>
>         Attachments: apicheck-hadoop-0.20.204.0-0.24.0-SNAPSHOT.txt
>
>
> 0.20.20x to 0.23.0 will be a common upgrade path, so we should document any incompatible API changes that will affect users.

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