Bugfix - Metrics API / aggregate from kubernetes service endpoint slices : add missing final semaphore acquisition

[julianguinard]

this relates to discussion #6565 (comment) of PR 6565

the final semaphore acquisition was still missing, which resulted in loop not waiting until all metrics were gathered from each metrics API server

Checklist

• I have verified that my change is according to the deprecations & breaking changes policy
• Commits are signed with Developer Certificate of Origin (DCO - learn more)

[github-actions]

Thank you for your contribution! 🙏

Please understand that we will do our best to review your PR and give you feedback as soon as possible, but please bear with us if it takes a little longer as expected.

While you are waiting, make sure to:

• Add an entry in our changelog in alphabetical order and link related issue
• Update the documentation, if needed
• Add unit & e2e tests for your changes
• GitHub checks are passing
• Is the DCO check failing? Here is how you can fix DCO issues

Once the initial tests are successful, a KEDA member will ensure that the e2e tests are run. Once the e2e tests have been successfully completed, the PR may be merged at a later date. Please be patient.

Learn more about our contribution guide.

[snyk-io]

✅ Snyk checks have passed. No issues have been found so far.

Status	Scanner	Critical	High	Medium	Low	Total (0)
✅	Open Source Security	0	0	0	0	0 issues

💻 Catch issues earlier using the plugins for VS Code, JetBrains IDEs, Visual Studio, and Eclipse.

[rickbrouwer]

/run-e2e metrics_api
Update: You can check the progress here

[julianguinard]

thanks @rickbrouwer , e2e passed successfully.

[rickbrouwer]

Thanks! lgtm!

[wozniakjan]

lgtm, thanks!

[Copilot]

Pull request overview

This PR fixes a synchronization bug in the metrics API scaler where the function would not wait for all goroutines to complete before aggregating results from multiple Kubernetes service endpoints. The fix adds a final semaphore acquisition to ensure all metrics have been gathered before proceeding.

Key Changes:

• Added final semaphore acquisition to wait for all goroutines to complete their work
• Added debug logging to track the start and end of endpoint iteration

Comments suppressed due to low confidence (1)

pkg/scalers/metrics_api_scaler.go:453

• The nbErrors and expectedNbMetrics variables are accessed without mutex protection after the semaphore acquisition. While the semaphore should ensure goroutines have completed, if the semaphore acquisition fails (line 442-444), these variables may still be modified by running goroutines, creating a race condition. Consider protecting these reads with the mutex or returning early if semaphore acquisition fails.

	if nbErrors > 0 && nbErrors == len(endpointsUrls) {
		err = fmt.Errorf("could not get any metric successfully from the %d provided endpoints", len(endpointsUrls))
	}
	if s.metadata.AggregationType == AverageAggregationType {
		aggregation /= float64(expectedNbMetrics)
	}
	s.logger.V(1).Info(fmt.Sprintf("fetched %d metrics out of %d endpoints from kubernetes service : %s is %v\n", expectedNbMetrics, len(endpointsUrls), s.metadata.AggregationType, aggregation))

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.