pnowojski opened a new pull request #18420:
URL: https://github.com/apache/flink/pull/18420
Previously, if there was a node that was self-unioned with itself,
it was creating a situation with two identical StreamEdges. Both
with the same partitioning, from the same source node to the same
target node.
This was causing issues when constructing output collectors and
picking the correct RecordWriters, as StreamTask was not able to
uniquely identify given StreamEdge and was assigning the same
RecordWriter to both of the edges. As a result all stream elements
were sent twice through the same RecordWriter. It was actually pretty
harmless apart of calculating the combined watermark downstream,
since all watermarks were always comming just from one single
edge/inputgate, and the unused edges were always stuck with
min watermark.
As a solution we are making sure that StreamEdges are unique
by introducing a uniqueId field, incremented for every pair
of StreamEdges connecting the same node.
## Verifying this change
This change adds a new `checkState` for early detection of similar problems
and a new ITCase.
## Does this pull request potentially affect one of the following parts:
- Dependencies (does it add or upgrade a dependency): (yes / **no**)
- The public API, i.e., is any changed class annotated with
`@Public(Evolving)`: (yes / **no**)
- The serializers: (yes / **no** / don't know)
- The runtime per-record code paths (performance sensitive): (yes / **no**
/ don't know)
- Anything that affects deployment or recovery: JobManager (and its
components), Checkpointing, Kubernetes/Yarn, ZooKeeper: (yes / **no** / don't
know)
- The S3 file system connector: (yes / **no** / don't know)
## Documentation
- Does this pull request introduce a new feature? (yes / **no**)
- If yes, how is the feature documented? (**not applicable** / docs /
JavaDocs / not documented)
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