Stephan Ewen created FLINK-5747:
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Summary: Eager Scheduling should deploy all Tasks together
Key: FLINK-5747
URL: https://issues.apache.org/jira/browse/FLINK-5747
Project: Flink
Issue Type: Bug
Components: JobManager
Affects Versions: 1.2.0
Reporter: Stephan Ewen
Assignee: Stephan Ewen
Fix For: 1.3.0
Currently, eager scheduling immediately triggers the scheduling for all
vertices and their subtasks in topological order.
This has two problems:
- This works only, as long as resource acquisition is "synchronous". With
dynamic resource acquisition in FLIP-6, the resources are returned as Futures
which may complete out of order. This results in out-of-order (not in
topological order) scheduling of tasks which does not work for streaming.
- Deploying some tasks that depend on other tasks before it is clear that the
other tasks have resources as well leads to situations where many
deploy/recovery cycles happen before enough resources are available to get the
job running fully.
For eager scheduling, we should allocate all resources in one chunk and then
deploy once we know that all are available.
As a follow-up, the same should be done per pipelined component in lazy batch
scheduling as well. That way we get lazy scheduling across blocking boundaries,
and bulk (gang) scheduling in pipelined subgroups.
This also does not apply for efforts of fine grained recovery, where individual
tasks request replacement resources.
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