rkhachatryan opened a new pull request #13351:
URL: https://github.com/apache/flink/pull/13351
## What is the purpose of the change
This is a *draft* PR to implement sequential reading of channel state.
There are still some unknowns:
- whether we want sequential read (as it might complicate rescaling)
- failing `StreamTaskSelectiveReadingITCase` (below)
The last change (unconditional reading of state, see changelog below)
currently fails `StreamTaskSelectiveReadingITCase`.
The problem also affects production so should be fixed externally; consider
the following case:
- Two IntputGates
- Input selection is not ALL (say FIRST initially)
- Unaligned Checkpoints ON
- on recovery, there are "parts" of records in all channels (actually 1 is
enough I think)
What happens:
1. StreamTask initiates recovery and scedule partition request upon it's end
2. All gates and channels will receive buffers from StateReader
3. All channels of a single gate will consume those state buffers -
completing that gate's StateConsumedFuture
4. InputProcessor will return NOTHING_AVAILABLE (see
StreamTwoInputProcessor.getInputStatus)
5. StreamTask will suspend its default action
6. State of the 2nd gate won't be consumed - so its StateConsumedFutures
won't be completed - so no partitions will be requested
Solution: request partitions independently for each channel.
## Brief change log
1. Implement sequntial reading - without dropping any existing code (to ease
review)
1. Remove old tests, methods in network-classes and eventually old reader
1. Explicitly check state in Recovered channels to disallow premature
conversion - to reduce needed test coverage
1. Unconditionally read channel state in `StreamTask` - to reduce needed
test coverage
## Verifying this change
- Added `SequentialChannelStateReaderImplTest` and
`ChannelStateChunkReaderTest` for the new code.
- Added `RecoveredInputChannelTest` to check that conversion is not
permitted untill fully recovered and state consumed
- State in `StreamTask` is read unconditionally, so some tests are eliminated
## Does this pull request potentially affect one of the following parts:
- Dependencies (does it add or upgrade a dependency): no
- The public API, i.e., is any changed class annotated with
`@Public(Evolving)`: (yes / no)
- The serializers: no
- The runtime per-record code paths (performance sensitive): no
- Anything that affects deployment or recovery: JobManager (and its
components), Checkpointing, Kubernetes/Yarn/Mesos, ZooKeeper: yes
- The S3 file system connector: no
## Documentation
- Does this pull request introduce a new feature? no
- If yes, how is the feature documented? no
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