[FLINK-16949] Enhance AbstractStreamOperatorTestHarness to use customized TtlTimeProvider

[Myasuka]

What is the purpose of the change

Enhance specific UTs to use customized TtlTimeProvider to simulate changed current time. This would introduce some changes to AbstractStreamOperatorTestHarness and add new StreamTaskStateInitializerTestImpl for different state backends.

Brief change log

Introduce some changes to AbstractStreamOperatorTestHarness and add new StreamTaskStateInitializerTestImpl for different state backends.

Verifying this change

This change added tests and can be verified as follows:

AbstractStreamOperatorTestHarnessTest#testSetTtlTimeProvider

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): no
• The public API, i.e., is any changed class annotated with @Public(Evolving): no
• The serializers: no
• The runtime per-record code paths (performance sensitive): no
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn/Mesos, ZooKeeper: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? no
• If yes, how is the feature documented? not applicable

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Last check on commit 6687976 (Thu Apr 02 18:53:18 UTC 2020)

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[azagrebin]

Why not to inject this in the constructor of StreamTaskStateInitializerImpl?

[Myasuka]

I just don't want to introduce too many changes here. If we plan to inject this as a filed, I am in favor of moving TtlTimeProvider at operator level (by changing StreamTaskStateInitializer#streamOperatorStateContext) but not in the constructor which was FLINK-14156 fixed.

[azagrebin]

I think either approach can be refactored in future.
Using constructor is the usual way how we inject dependencies for tests. The inheritance is usually used to change more complicated internal behaviour.
You could also keep the current constructor and add another one annotated with @VisibleForTesting which could accept the custom TtlTimeProvider field.

[Myasuka]

There existed another problem why we not change the constructor of StreamTaskStateInitializerImpl.
Current AbstractStreamOperatorTestHarness is not created from a builder, and once a new AbstractStreamOperatorTestHarness is created, the inner streamTaskStateInitializer has been created with the default TtlTimeProvider. Even we set ttl time provider to AbstractStreamOperatorTestHarness later, the inner streamTaskStateInitializer would not notice the changed ttl time provider unless we call AbstractStreamOperatorTestHarness#setup to re-create the inner streamTaskStateInitializer.
However, AbstractStreamOperatorTestHarness#setup actually call a deprecated SetupableStreamOperator#setup interface.
In a nutshell, unless we refactor how we build AbstractStreamOperatorTestHarness, to make the customized ttl time provider take effect, we must call AbstractStreamOperatorTestHarness#setup each time which might already be treated as a deprecated interface.

[azagrebin]

Then I think it makes sense to consider builders to avoid adding more harness constructors.

[wuchong]

Why not AbstractStreamOperatorTestHarness always use a mocked TtlTimeProvider? Just like always use the TestProcessingTimeService. Then we don't need to re-create the inner streamTaskStateInitializer.

I also prefer the way to set processing time on the harness object AbstractStreamOperatorTestHarness#setProcessingTime instead of on other object mockTtlTimeProvider.setCurrentTimeStamp(0L). We can provide a method setStateTtlTime() on the AbstractStreamOperatorTestHarness too.

[azagrebin]

This would indeed work. This is not flexible in general but may be good enough and we already have it for processing time.

[Myasuka]

I think @wuchong 's suggestion is also a available choice. However, I think FLINK-17011 is the most clean solution to clean up these test code. Although I have to admit that PR #11676 is a bit large for reviewing.

[wuchong]

What about going with this approach first? This can be merged faster and unblock other works. We can also continue the cleanup work using new builders after that, and expose custom time provider in builders to make it more flexible.

[wuchong]

Thanks for the updating @Myasuka , LGTM. Just left a minor comment.

[wuchong]

Merging...