B Wyatt created FLINK-3974:
------------------------------
Summary: 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
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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