Zhu Zhu created FLINK-14236:
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             Summary: Make LazyFromSourcesSchedulingStrategy do lazy scheduling 
only based on partition state
                 Key: FLINK-14236
                 URL: https://issues.apache.org/jira/browse/FLINK-14236
             Project: Flink
          Issue Type: Sub-task
          Components: Runtime / Coordination
    Affects Versions: 1.10.0
            Reporter: Zhu Zhu
             Fix For: 1.10.0


The philosophy of lazy_from_sources scheduling is to schedule a task when its 
inputs are ready, i.e. when needed result partitions are consumable. It 
actually does not directly care whether a task is finished, though a finished 
task will lead its partitions to be consumable.

The {{LazyFromSourcesSchedulingStrategy}} currently does lazy scheduling in two 
ways:
1. trigger scheduling on FINISHED execution state for blocking partition 
consumers
2. trigger scheduling on partition consumable events for pipelined partition 
consumers
This makes the scheduling decision a bit messy. And it also requires the 
{{LazyFromSourcesSchedulingStrategy}} to manage the partition state by itself, 
to decide when a partition is consumable, which is not good.

I'd propose to make {{LazyFromSourcesSchedulingStrategy}} do lazy scheduling 
only based on partition state. This can make the scheduling decision making 
clearer and relieve {{LazyFromSourcesSchedulingStrategy}} from partition state 
management.

This work requires FLINK-14234 so that all partition consumable events can be 
notified.




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