[jira] [Created] (FLINK-3646) Use Processing-Time Clock in Window Assigners/Triggers

[Shang Yuanchun (Jira)]

Aljoscha Krettek created FLINK-3646:
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             Summary: Use Processing-Time Clock in Window Assigners/Triggers
                 Key: FLINK-3646
                 URL: https://issues.apache.org/jira/browse/FLINK-3646
             Project: Flink
          Issue Type: Sub-task
          Components: Streaming
    Affects Versions: 1.0.0
            Reporter: Aljoscha Krettek


This is part of the effort to improve Window Triggers in Flink. We should replace all usage of {{System.currentTimeMillis()}} by a provided clock implementation. This way we can use a deterministic testing clock to verify the behavior of processing-time windowing components in unit tests.

This requires the following changes:

- Change {{StreamTask}} to have a {{Clock}} (name is WIP). By default this clock will use {{System.currentTimeMillis()}}. The clock must also provide an interface to register processing-time triggers, this is currently handled directly by {{StreamTask}} but must now also be handled by an external Clock
- Change API of {{WindowAssigner}} to take a context object that allows it to query the current processing time. This can be an abstract class {{AssignerContext}} with a single method {{long currentProcessingTime()}}
- Add a method {{long currentProcessingTime()}} in {{TriggerContext}}, change {{TriggerContext}} to use the clock methods provided by {{StreamTask}} and forwarded by {{WindowOperator}}
- Change processing-time triggers to use the new methods
- Change {{WindowOperator}} to support these changes



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