AHeise opened a new pull request #13228:
URL: https://github.com/apache/flink/pull/13228
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## What is the purpose of the change
Currently, netty threads and task thread are both accessing Unaligner. Netty
thread access it indirectly through `BufferReceivedListener`. Thus, we need
some costly synchronization and weaken the threading model of the Unaligner.
This PR mitigates it by letting priority buffers use the same handover
protocol as regular buffers. Instead buffers are reordered where needed an
additional wake-up mechanism is used for priority events, such that they can
interrupt regular buffer processing.
## Brief change log
- Adding specific buffer data type for priority events.
- Adding priority flags to hand-over protocols (`BufferAndAvailability`,
`BufferAndBacklog`, `InputWithData`, ...) directly or indirectly.
- Reordering buffers, channels, and gates on priority buffers, such that
they are pulled before any non-priority buffer.
- Adding a data structure `PriorityDeque` to support such reordering.
- Adding priority notifications on input/output.
- Handling priority notifications in `CheckpointedInputGate` (moved out from
Unaligner). Generalized hand-over of events from `CheckpointedInputGate` to
`StreamTaskNetworkInput`, such that all events are forwarded.
- Removing synchronizations from Unaligner.
- Moving spill handling from `StreamTaskNetworkInput` to Unaligner.
- Removing `BufferReceivedListener` and letting Unaligner react on in-flight
data.
## Verifying this change
- Added/modified a bunch of unit tests.
- UnalignedCheckpointITCase still covering along with all other ITCases and
e2e (using unaligned checkpoints by default).
## 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/Mesos, 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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