prometheus: add support for external Prometheus URLs by Tusharjamdade · Pull Request #494 · headlamp-k8s/plugins

Tusharjamdade · 2026-01-24T18:40:46Z

Allows configuring Prometheus using a full HTTP/HTTPS URL in addition to namespace/service:port.
This enables connecting clusters to external or shared Prometheus instances.
Keeps existing Kubernetes service-based configuration working.
Fixes #377.

Tusharjamdade · 2026-01-25T05:38:49Z

Hi @illume, could you please review this when you have a moment?

Copilot

Pull request overview

This PR extends the Prometheus plugin so clusters can use either in-cluster Kubernetes services or external Prometheus endpoints configured via full HTTP/HTTPS URLs, while updating the settings UI and request logic accordingly.

Changes:

Update getPrometheusPrefix to resolve either a full HTTP/HTTPS Prometheus URL or a Kubernetes namespace/service:port address into the prefix used for querying.
Enhance fetchMetrics to detect when the prefix is an external URL and route requests directly via fetch instead of the Kubernetes API proxy, including integration with the optional subPath.
Broaden settings validation and helper text to accept and guide users toward both namespace/service:port and HTTP/HTTPS URL formats for the Prometheus address.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
`prometheus/src/util.ts`	Adjusts cluster configuration helpers so Prometheus prefixes can be resolved from either an HTTP/HTTPS URL or a Kubernetes service-style address; also still provides interval, resolution, and subpath helpers used by charts.
`prometheus/src/request.tsx`	Adds URL detection and extends `fetchMetrics` to support direct calls to external Prometheus URLs while preserving the existing in-cluster Kubernetes proxy behavior.
`prometheus/src/components/Settings/Settings.tsx`	Expands settings validation and UI copy to accept both Kubernetes service addresses and full HTTP/HTTPS URLs for configuring the Prometheus endpoint.

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Copilot · 2026-01-30T13:01:32Z

prometheus/src/request.tsx

  if (data.query) {
    params.append('query', data.query);
  }
-  var url = `/api/v1/namespaces/${data.prefix}/proxy/api/v1/query_range?${params.toString()}`;
-  if (data.subPath && data.subPath !== '') {
-    if (data.subPath.startsWith('/')) {
-      data.subPath = data.subPath.slice(1);
+
+  const isExternal = isHttpUrl(data.prefix);
+  var url: string;
+


The implementation of fetchMetrics now supports both in-cluster Kubernetes proxy prefixes and full HTTP/HTTPS URLs (via isHttpUrl), but the JSDoc above still documents data.prefix only as a "namespace prefix". To keep the API contract clear for future callers, consider updating the JSDoc to explicitly describe that prefix can be either a Kubernetes proxy prefix (e.g. namespace/services/service:port) or a full Prometheus base URL, and how that interacts with the optional subPath.

prometheus/src/util.ts

prometheus/src/request.tsx

Copilot · 2026-01-30T13:01:32Z

prometheus/src/util.ts

 export async function getPrometheusPrefix(cluster: string): Promise<string | null> {
-  // check if cluster has autoDetect enabled
-  // if so return the prometheus pod address
  const clusterData = getClusterConfig(cluster);
-  if (clusterData?.autoDetect) {
-    const prometheusEndpoint = await isPrometheusInstalled();
-    if (prometheusEndpoint.type === KubernetesType.none) {
-      return null;
+  if (clusterData?.address) {
+    const address = clusterData.address.trim().replace(/\/$/, '');
+
+    if (address.startsWith('http://') || address.startsWith('https://')) {
+      return address;
    }
-    const prometheusPortStr = prometheusEndpoint.port ? `:${prometheusEndpoint.port}` : '';
-    return `${prometheusEndpoint.namespace}/${prometheusEndpoint.type}/${prometheusEndpoint.name}${prometheusPortStr}`;
-  }

-  if (clusterData?.address) {
-    const [namespace, service] = clusterData?.address.split('/');
-    return `${namespace}/services/${service}`;
+    const parts = address.split('/');
+    if (parts.length === 2) {
+      const [namespace, service] = parts;
+      return `${namespace}/services/${service}`;
+    }
  }
  return null;
 }


getPrometheusPrefix now contains additional logic for handling full HTTP/HTTPS URLs and parsing manual Kubernetes service addresses, but there are no unit tests covering this behavior even though util.ts already has tests for other helpers (see util.test.ts). To avoid regressions (especially around URL vs. namespace/service handling and edge cases like trailing slashes or malformed addresses), consider adding focused tests for this function exercising both external-URL and in-cluster service configurations.

This is a nice to have, but shouldn't block merging IMHO.

illume

Thanks for this.

Could you please check the open review comments?

Please see the git commit guidelines and look at other git log messages.

@Tusharjamdade It seems there is also a git conflict. Can you please rebase and fix the conflicts?

Signed-off-by: Tusharjamdade <tusharnjamdade@gmail.com>

Tusharjamdade · 2026-02-01T19:46:00Z

Hi @illume, apologies for the multiple commits, I was running the formatter incorrectly earlier.

I’ve now updated the code as per the review. Please take a look when you get a chance.

illume

Thanks for the changes.

Could you please squash the commits?

Also, let us know if the open review comments have been addressed or not?

skoeva

this will be completed in #508

Tusharjamdade force-pushed the prometheus-url branch from d46e242 to 816ce8a Compare January 24, 2026 18:45

illume requested a review from Copilot January 30, 2026 12:57

Copilot started reviewing on behalf of illume January 30, 2026 12:58 View session

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illume requested changes Jan 30, 2026

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illume added the prometheus prometheus plugin related issues label Feb 1, 2026

Tusharjamdade added 3 commits February 1, 2026 19:05

feat: add support for external Prometheus URLs

9b11486

Signed-off-by: Tusharjamdade <tusharnjamdade@gmail.com>

feat: add support for external Prometheus URLs

c81d457

Signed-off-by: Tusharjamdade <tusharnjamdade@gmail.com>

feat: add support for external Prometheus URLs

a381dbf

Signed-off-by: Tusharjamdade <tusharnjamdade@gmail.com>

Tusharjamdade force-pushed the prometheus-url branch from 816ce8a to a381dbf Compare February 1, 2026 19:16

prometheus: fix import order to satisfy lint rules

eda577e

Signed-off-by: Tusharjamdade <tusharnjamdade@gmail.com>

Tusharjamdade force-pushed the prometheus-url branch from ab1df7f to eda577e Compare February 1, 2026 19:23

Tusharjamdade added 3 commits February 1, 2026 19:27

prometheus: format files to satisfy prettier checks

cf2172f

Signed-off-by: Tusharjamdade <tusharnjamdade@gmail.com>

prometheus: format files to satisfy prettier checks

ac43655

Signed-off-by: Tusharjamdade <tusharnjamdade@gmail.com>

prometheus: format files to satisfy prettier checks

06fbd0d

Signed-off-by: Tusharjamdade <tusharnjamdade@gmail.com>

illume requested changes Feb 2, 2026

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skoeva mentioned this pull request Feb 3, 2026

prometheus: Add support for external Prometheus URLs #508

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skoeva reviewed Feb 9, 2026

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skoeva closed this Feb 9, 2026

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prometheus: add support for external Prometheus URLs#494

prometheus: add support for external Prometheus URLs#494
Tusharjamdade wants to merge 7 commits intoheadlamp-k8s:mainfrom
Tusharjamdade:prometheus-url

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