EugeneYushin commented on a change in pull request #6646: [FLINK-10050] Support
allowedLateness in CoGroupedStreams
URL: https://github.com/apache/flink/pull/6646#discussion_r217879647
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File path:
flink-streaming-java/src/main/java/org/apache/flink/streaming/api/datastream/JoinedStreams.java
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@@ -239,7 +245,17 @@ protected WithWindow(DataStream<T1> input1,
@PublicEvolving
public WithWindow<T1, T2, KEY, W> evictor(Evictor<? super
TaggedUnion<T1, T2>, ? super W> newEvictor) {
return new WithWindow<>(input1, input2, keySelector1,
keySelector2, keyType,
- windowAssigner, trigger, newEvictor);
+ windowAssigner, trigger, newEvictor,
allowedLateness);
+ }
+
+ /**
+ * Sets the time by which elements are allowed to be late.
+ * @see WindowedStream#allowedLateness(Time)
+ */
+ @PublicEvolving
+ public WithWindow<T1, T2, KEY, W> allowedLateness(Time
newLateness) {
Review comment:
Check for null in this place breaks current logic of CoGroup/Join classes.
CoGroup has no checks for nulls directly in `evictor`/`trigger` methods and
validates during delegation:
https://github.com/apache/flink/blob/98412a5f7227d7694c727847727f9434bcca4e92/flink-streaming-java/src/main/java/org/apache/flink/streaming/api/datastream/CoGroupedStreams.java#L344
I do null check there as well for `allowedLateness` field.
In the same time, Join.apply delegates to CoGroup.apply:
https://github.com/apache/flink/blob/98412a5f7227d7694c727847727f9434bcca4e92/flink-streaming-java/src/main/java/org/apache/flink/streaming/api/datastream/JoinedStreams.java#L314).
To be consistent, we also should add null checks for evictor and trigger.
Adding null checks directly in setters/constructor breaks chain of calls in
`apply` methods (for evictor/trigger/allowedLateness) and requires clumsy
if-else conditions for each nullable field separately.
Both CoGroup and Join allow null for trigger/evictor (and I've added
allowedLateness following the same approach) but don't pass validation during
calls to `apply(...)`.
As a result of null check for `allowedLateness` inside setter, we have
errors for the following scenario:
https://github.com/apache/flink/blob/8674b69964eae50cad024f2c5caf92a71bf21a09/flink-streaming-scala/src/test/scala/org/apache/flink/streaming/api/scala/CoGroupJoinITCase.scala#L151
It breaks when user doesn't specify any of trigger/evictor/allowedLateness.
At the same time, these fields are optional and have defaults in
WindowedStream. Unfortunately, default for allowedLateness in WindowedStream
has private modificator (and I don't think it's a good practice to set default
when user passed null by mistake).
Please, let me know you thoughts.
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