[jira] [Assigned] (FLINK-3974) enableObjectReuse fails when an operator chains to multiple downstream operators

["Aljoscha Krettek (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/FLINK-3974?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Aljoscha Krettek reassigned FLINK-3974:
---------------------------------------

    Assignee: Aljoscha Krettek

> enableObjectReuse fails when an operator chains to multiple downstream operators
> --------------------------------------------------------------------------------
>
>                 Key: FLINK-3974
>                 URL: https://issues.apache.org/jira/browse/FLINK-3974
>             Project: Flink
>          Issue Type: Bug
>          Components: DataStream API
>    Affects Versions: 1.0.3
>            Reporter: B Wyatt
>            Assignee: Aljoscha Krettek
>             Fix For: 1.1.0
>
>         Attachments: ReproFLINK3974.java, bwyatt-FLINK3974.1.patch
>
>
> Given a topology that looks like this:
> {code:java}
> DataStream<A> input = ...
> input
>     .map(MapFunction<A,B>...)
>     .addSink(...);
> input
>     .map(MapFunction<A,C>...)
>     ​.addSink(...);
> {code}
> enableObjectReuse() will cause an exception in the form of {{"java.lang.ClassCastException: B cannot be cast to A"}} to be thrown.
> It looks like the input operator calls {{Output<StreamRecord<A>>.collect}} which attempts to loop over the downstream operators and process them.
> However, the first map operation will call {{StreamRecord<>.replace}} which mutates the value stored in the StreamRecord<>.  
> As a result, when the {{Output<StreamRecord<A>>.collect}} call passes the {{StreamRecord<A>}} to the second map operation it is actually a {{StreamRecord<B>}} and behaves as if the two map operations were serial instead of parallel.



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