[jira] [Commented] (FLINK-4316) Make flink-core independent of Hadoop

["Stephan Ewen (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-4316?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15409384#comment-15409384 ] 

Stephan Ewen commented on FLINK-4316:
-------------------------------------

An alternative would be to copy the Hadoop {{Writable}} type (simple interface) into {{link-core}}. We did that before, it works well and is a much easier solution (no reflection work), but comes with two issues:
  - We need to carry that class in the flink codebase
  - There will be multiple versions of {{Writable}} and in theory, these could lead to class cast exceptions.

> Make flink-core independent of Hadoop
> -------------------------------------
>
>                 Key: FLINK-4316
>                 URL: https://issues.apache.org/jira/browse/FLINK-4316
>             Project: Flink
>          Issue Type: Bug
>          Components: Core
>    Affects Versions: 1.1.0
>            Reporter: Stephan Ewen
>            Assignee: Stephan Ewen
>             Fix For: 1.2.0
>
>
> We want to gradually reduce the hard and heavy mandatory dependencies in Hadoop. Hadoop will still be part of (most) flink downloads, but the API projects should not have a hard dependency on Hadoop.
> I suggest to start with {{flink-core}}, because it only depends on Hadoop for the {{Writable}} type, to support seamless operation of Hadoop types.
> I propose to move all {{WritableTypeInfo}}-related classes to the {{flink-hadoop-compatibility}} project and access them via reflection in the {{TypeExtractor}}.
> That way, {{Writable}} types will be out of the box supported if users have the {{flink-hadoop-compatibility}} project in the classpath.



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