Akshat-Jain opened a new pull request, #17373:
URL: https://github.com/apache/druid/pull/17373
### Description
With the changes made in #17038, we missed a flow where multiple frames
could be written to the output channel in a single iteration of
`WindowOperatorQueryFrameProcessor#runIncrementally`. This violates the
contract of `runIncrementally()` and leads to the following error: `Channel has
no capacity`
<details>
<summary>Sample stacktrace</summary>
```
2024-10-18T00:06:27,410 WARN [MultiStageQuery-test-controller-client]
org.apache.druid.msq.exec.WorkerImpl - Work failed; stage 2; task
query-dummy-worker0_0; host 123:8080: UnknownError: java.lang.RuntimeException:
org.apache.druid.java.util.common.ISE: Channel has no capacity
java.lang.RuntimeException: org.apache.druid.java.util.common.ISE: Channel
has no capacity
at org.apache.druid.java.util.common.Either.valueOrThrow(Either.java:95)
at
org.apache.druid.frame.processor.FrameProcessorExecutor$1ExecutorRunnable.runProcessorNow(FrameProcessorExecutor.java:271)
at
org.apache.druid.frame.processor.FrameProcessorExecutor$1ExecutorRunnable.run(FrameProcessorExecutor.java:141)
at org.apache.druid.msq.exec.WorkerImpl$2$2.run(WorkerImpl.java:900)
at
java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
at
java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
at java.base/java.lang.Thread.run(Thread.java:829)
Caused by: org.apache.druid.java.util.common.ISE: Channel has no capacity
at
org.apache.druid.frame.channel.BlockingQueueFrameChannel$Writable.write(BlockingQueueFrameChannel.java:139)
at
org.apache.druid.msq.indexing.CountingWritableFrameChannel.write(CountingWritableFrameChannel.java:50)
at
org.apache.druid.msq.querykit.WindowOperatorQueryFrameProcessor.flushFrameWriter(WindowOperatorQueryFrameProcessor.java:302)
at
org.apache.druid.msq.querykit.WindowOperatorQueryFrameProcessor.writeRacToFrame(WindowOperatorQueryFrameProcessor.java:262)
at
org.apache.druid.msq.querykit.WindowOperatorQueryFrameProcessor.flushAllRowsAndCols(WindowOperatorQueryFrameProcessor.java:232)
at
org.apache.druid.msq.querykit.WindowOperatorQueryFrameProcessor.runIncrementally(WindowOperatorQueryFrameProcessor.java:150)
at
org.apache.druid.msq.counters.CpuTimeAccumulatingFrameProcessor.runIncrementally(CpuTimeAccumulatingFrameProcessor.java:66)
at
org.apache.druid.frame.processor.FrameProcessors$1FrameProcessorWithBaggage.runIncrementally(FrameProcessors.java:72)
at
org.apache.druid.frame.processor.FrameProcessorExecutor$1ExecutorRunnable.runProcessorNow(FrameProcessorExecutor.java:239)
... 5 more
```
</details>
We missed this flow:
1. We read the input channel
2. We call `runAllOpsOnBatch()`
3. If after step (1), the input channel was finished, then the
operatorChain's receiver's completed() method will get called, which would call
`flushAllRowsAndCols()`, hence writing to the output channel.
4. After this, we end up calling `flushAllRowsAndCols()` again, missing the
fact that there's a chance that the input channel might have finished. This
ends up attempting to write another frame to the output channel, causing the
`Channel has no capacity` error.
This PR fixes the above problematic flow by checking if the input channel is
finished. If it's finished, we re-run `runIncrementally()` instead of step 4.
<hr>
This PR has:
- [x] been self-reviewed.
- [ ] added documentation for new or modified features or behaviors.
- [ ] a release note entry in the PR description.
- [ ] added Javadocs for most classes and all non-trivial methods. Linked
related entities via Javadoc links.
- [ ] added or updated version, license, or notice information in
[licenses.yaml](https://github.com/apache/druid/blob/master/dev/license.md)
- [ ] added comments explaining the "why" and the intent of the code
wherever would not be obvious for an unfamiliar reader.
- [ ] added unit tests or modified existing tests to cover new code paths,
ensuring the threshold for [code
coverage](https://github.com/apache/druid/blob/master/dev/code-review/code-coverage.md)
is met.
- [ ] added integration tests.
- [ ] been tested in a test Druid cluster.
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