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https://issues.apache.org/jira/browse/FLINK-14607?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Zhu Zhu updated FLINK-14607:
----------------------------
Description:
Currently a pending request can only be fulfilled when a physical
slot({{AllocatedSlot}}) becomes available in {{SlotPool}}.
A shared slot however, cannot be used to fulfill pending requests even if it
becomes qualified. This may lead to resource deadlocks in certain cases.
For example, running job A(parallelism=2) --(pipelined)--> B(parallelism=2)
with 1 slot only, all vertices are in the same slot sharing group, here's what
may happen:
1. Schedule A1 and A2. A1 acquires the only slot, A2's slot request is pending
because a slot cannot host 2 instances of the same JobVertex at the same time.
Shared slot status: \{A1\}
2. A1 produces data and triggers the scheduling of B1. Shared slot status {A1,
B1}
3. A1 finishes. Shared slot status {B1}
4. B1 cannot finish since A2 has not finished, while A2 cannot get launched due
to no physical slot becomes available, even though the slot is qualified for
host it now. A resource deadlock happens.
Maybe we should improve {{SlotSharingManager}}. One a task slot is released,
its root {{MultiTaskSlot}} should be used to try fulfilling existing pending
task slots from other pending root slots({{unresolvedRootSlots}}) in this
{{SlotSharingManager}}(means in the same slot sharing group).
We need to be careful to not cause any failures, and do not violate colocation
constraints.
cc [~trohrmann]
was:
Currently a pending request can only be fulfilled when a physical
slot({{AllocatedSlot}}) becomes available in {{SlotPool}}.
A shared slot however, cannot be used to fulfill pending requests even if it
becomes qualified. This may lead to resource deadlocks in certain cases.
For example, running job A(parallelism=2) --(pipelined)--> B(parallelism=2)
with 1 slot only, all vertices are in the same slot sharing group, here's what
may happen:
1. Schedule A1 and A2. A1 acquires the only slot, A2's slot request is pending
because a slot cannot host 2 instances of the same JobVertex at the same time.
Shared slot status {A1}
2. A1 produces data and triggers the scheduling of B1. Shared slot status {A1,
B1}
3. A1 finishes. Shared slot status {B1}
4. B1 cannot finish since A2 has not finished, while A2 cannot get launched due
to no physical slot becomes available, even though the slot is qualified for
host it now. A resource deadlock happens.
Maybe we should improve {{SlotSharingManager}}. One a task slot is released,
its root {{MultiTaskSlot}} should be used to try fulfilling existing pending
task slots from other pending root slots({{unresolvedRootSlots}}) in this
{{SlotSharingManager}}(means in the same slot sharing group).
We need to be careful to not cause any failures, and do not violate colocation
constraints.
cc [~trohrmann]
> SharedSlot cannot fulfill pending slot requests before it's completely
> released
> -------------------------------------------------------------------------------
>
> Key: FLINK-14607
> URL: https://issues.apache.org/jira/browse/FLINK-14607
> Project: Flink
> Issue Type: Bug
> Components: Runtime / Coordination
> Affects Versions: 1.10.0, 1.9.1
> Reporter: Zhu Zhu
> Priority: Major
>
> Currently a pending request can only be fulfilled when a physical
> slot({{AllocatedSlot}}) becomes available in {{SlotPool}}.
> A shared slot however, cannot be used to fulfill pending requests even if it
> becomes qualified. This may lead to resource deadlocks in certain cases.
> For example, running job A(parallelism=2) --(pipelined)--> B(parallelism=2)
> with 1 slot only, all vertices are in the same slot sharing group, here's
> what may happen:
> 1. Schedule A1 and A2. A1 acquires the only slot, A2's slot request is
> pending because a slot cannot host 2 instances of the same JobVertex at the
> same time. Shared slot status: \{A1\}
> 2. A1 produces data and triggers the scheduling of B1. Shared slot status
> {A1, B1}
> 3. A1 finishes. Shared slot status {B1}
> 4. B1 cannot finish since A2 has not finished, while A2 cannot get launched
> due to no physical slot becomes available, even though the slot is qualified
> for host it now. A resource deadlock happens.
> Maybe we should improve {{SlotSharingManager}}. One a task slot is released,
> its root {{MultiTaskSlot}} should be used to try fulfilling existing pending
> task slots from other pending root slots({{unresolvedRootSlots}}) in this
> {{SlotSharingManager}}(means in the same slot sharing group).
> We need to be careful to not cause any failures, and do not violate
> colocation constraints.
> cc [~trohrmann]
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