[hotfix] Tracks the number of pending manual compactions.

[littleeleventhwolf]

What is the purpose of the change

This pull request tracks the pendingManualCompactions in org.apache.flink.state.rocksdb.sstmerge.CompactionTracker:

Brief change log

• Currently, there is only pendingManualCompactions-- in the code.
• Add pendingManualCompactions++ to correct the logic.

Verifying this change

This change is a trivial rework / code cleanup without any test coverage.

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): (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, ZooKeeper: (no)
• The S3 file system connector: (no)

Documentation

• Does this pull request introduce a new feature? (no)

[flinkbot]

CI report:

• e768ec1 Azure: FAILURE

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[davidradl]

the method name does not seem correct. haveManualCompactions refers to runningManualCompactions and pendingManualCompactions. I suggest scheduleManualCompaction.

[davidradl]

can we add some unit tests for this class.
I am curious about the method

private synchronized void cancel() {
        pendingManualCompactions--;
    }

If the cancel can be called while it is running then the pending counter could go negative - as we have already decremented the pending counter when we incremented the running one.