Zhu Zhu created FLINK-17330:
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Summary: Avoid scheduling deadlocks caused by intra-logical-region
ALL-to-ALL blocking edges
Key: FLINK-17330
URL: https://issues.apache.org/jira/browse/FLINK-17330
Project: Flink
Issue Type: Sub-task
Components: Runtime / Coordination
Affects Versions: 1.11.0
Reporter: Zhu Zhu
Fix For: 1.11.0
Imagine a job like this:
A --(pipelined FORWARD)--> B --(blocking ALL-to-ALL)--> D
A --(pipelined FORWARD)--> C --(pipelined FORWARD)--> D
parallelism=2 for all vertices.
We will have 2 execution pipelined regions:
R1={A1, B1, C1, D1}, R2={A2, B2, C2, D2}
R1 has a cross-region input edge (B2->D1).
R2 has a cross-region input edge (B1->D2).
Scheduling deadlock will happen since we schedule a region only when all its
inputs are consumable (i.e. blocking partitions to be finished). Because R1 can
be scheduled only if R2 finishes, while R2 can be scheduled only if R1 finishes.
To avoid this, one solution is to force a logical pipelined region with
intra-region ALL-to-ALL blocking edges to form one only execution pipelined
region, so that there would not be cyclic input dependency between regions.
Besides that, we should also pay attention to avoid cyclic cross-region
POINTWISE blocking edges.
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