zihanx opened a new pull request, #15507:
URL: https://github.com/apache/lucene/pull/15507
## Summary
This PR enhances the `runOnMergeFinished` hook in `ConcurrentMergeScheduler`
to provide access to `OneMerge` and `MergeRateLimiter` parameters.
## Motivation
Currently, applications that subclass `ConcurrentMergeScheduler` to monitor
merge behavior have limited context in the `runOnMergeFinished` hook. The
`MergeRateLimiter` contains valuable metrics about merge performance
(pause time, throttling, MB/sec) that would be useful for:
- Monitoring merge performance in production
- Building custom metrics and dashboards
- Debugging merge-related issues
- Optimizing merge scheduler configurations
## Changes
- Changed `runOnMergeFinished` from package-private to `protected` to allow
subclassing
- Added `OneMerge merge` parameter for merge context
- Added `MergeRateLimiter rateLimiter` parameter to expose merge rate metrics
## Backward Compatibility
This is a breaking change for any code that currently overrides
`runOnMergeFinished`,
but since the method was package-private, external impact should be minimal.
## Example Use Case
Applications can now override this method to emit custom metrics:
```java
@Override
protected synchronized void runOnMergeFinished(MergeSource mergeSource,
OneMerge merge,
MergeRateLimiter
rateLimiter) {
super.runOnMergeFinished(mergeSource, merge, rateLimiter);
// Emit custom metrics
recordMetric("merge.paused.ns", rateLimiter.getTotalPausedNS());
recordMetric("merge.stopped.ns", rateLimiter.getTotalStoppedNS());
recordMetric("merge.mbps", rateLimiter.getMBPerSec());
}
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