Further filter Pod Metrics using labels

[at88mph]

Describe the bug
For efficiency, it would be very beneficial to enable the labelSelector when querying the Metrics for Pods.

Client Version
e.g. 24.0.0-SNAPSHOT

Kubernetes Version
e.g. 1.27.10

Java Version
e.g. Java 11

To Reproduce
Calling this:

final ApiClient client = Config.fromCluster();
final PodMetricsList = new Metrics(client).getPodMetrics("namespace");

Which could potentially query hundreds of Pods that are out of context, could be adapted to either use the ListOption directly, or, in my case, just the labelSelector:

final String labelSelector = "foo=bar, xyz!=abc"
final ApiClient client = Config.fromCluster();
final PodMetricsList = new Metrics(client).getPodMetrics("namespace", labelSelector);

Expected behavior
Reduce the items() in the PodMetricsList to just those that match the Namespace and Label Selector.

KubeConfig
Not applicable

Server (please complete the following information):

• OS: Debian Linux 12
• Environment: Docker
• Cloud: Self-hosted OpenStack

Additional context

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[Storm-Dev6]

Hi @at88mph,

Thanks for opening this feature request!

Filtering Pod Metrics by label selectors definitely makes sense to improve efficiency and reduce unnecessary data.

Currently, the official Kubernetes Java client’s Metrics API doesn’t directly support passing a labelSelector parameter in the getPodMetrics() method, but it could be extended or worked around like this:

1 - Workaround:
Retrieve all PodMetrics for the namespace, then filter in Java code by labels on the Pod metadata. This is less efficient but works for now.

2 - Better approach:
Use the underlying CoreV1 API to list Pods with a labelSelector, get their names, and then fetch metrics only for those Pods individually.

3 - Suggested improvement:
It would be great if the Metrics client adds support for labelSelector as an optional parameter, like you proposed.

Example snippet for workaround:

ApiClient client = Config.fromCluster();
Metrics metrics = new Metrics(client);

PodMetricsList allMetrics = metrics.getPodMetrics("namespace");
List<PodMetrics> filtered = allMetrics.getItems().stream()
.filter(p -> {
Map<String, String> labels = p.getMetadata().getLabels();
return labels != null && "bar".equals(labels.get("foo"));
})
.collect(Collectors.toList());

I recommend opening a PR or feature request for the client to support labelSelector officially.

If you want, I can help draft a PR or a more detailed workaround.

[at88mph]

Hi @Storm-Dev6. There is a PR open for it (#3999).

My Organization is new to the CLA signing and it took months for it to pass through the right people. I had to remove the stale state from that PR, but it should be good now. I would like to add a labelSelector at some point as well, to, say narrow down to GPU Nodes or something similar. This is a good start though.

[Storm-Dev6]

Hi @at88mph,

Thanks for the update and for pushing through the CLA process – completely understandable that it took some time.

Great to hear that #3999 is now unblocked! Adding labelSelector support is definitely a meaningful improvement, and I agree that future enhancements like filtering by nodeSelector (e.g., narrowing down to GPU nodes) would also be very valuable.

Let us know if there's anything we can do to support or review the PR going forward. Happy to help if needed!

Best regards, 😄