feat: add ServiceMonitor template for external Prometheus by NJX-njx · Pull Request #866 · vllm-project/production-stack

NJX-njx · 2026-03-04T10:37:48Z

Summary

Closes #606

Adds a conditional ServiceMonitor Helm template that allows teams with existing Prometheus stacks (e.g., kube-prometheus-stack, EKS Blueprint addons) to scrape vLLM metrics without deploying the bundled observability stack.

Motivation

Currently, vLLM metrics are only scraped when the bundled observability stack is installed. Users with pre-existing Prometheus setups must manually create and apply ServiceMonitor resources.

Configuration

New externalPrometheus section in values.yaml:

externalPrometheus:
  enabled: false
  namespace: "monitoring"
  labels:
    release: "kube-prometheus-stack"
  serviceSelector: {}
  portName: "service-port"
  path: "/metrics"
  interval: "30s"
  scrapeTimeout: ""

Changes

helm/templates/servicemonitor.yaml (new): Conditional ServiceMonitor template with namespaceSelector support for cross-namespace monitoring
helm/values.yaml: Added externalPrometheus configuration section
helm/values.schema.json: Added schema definition for externalPrometheus

Backward Compatibility

Fully backward compatible - disabled by default (enabled: false). Existing deployments are unaffected.

…ct#606) Add a conditional ServiceMonitor Helm template that allows teams with existing Prometheus stacks to scrape vLLM metrics without deploying the bundled observability stack. New configuration in values.yaml: - externalPrometheus.enabled: toggle ServiceMonitor creation - externalPrometheus.namespace: target namespace for the ServiceMonitor - externalPrometheus.labels: labels for Prometheus serviceMonitorSelector - externalPrometheus.serviceSelector: custom service selector - externalPrometheus.portName: service port name to scrape - externalPrometheus.path: metrics endpoint path - externalPrometheus.interval: scrape interval - externalPrometheus.scrapeTimeout: scrape timeout Files changed: - helm/templates/servicemonitor.yaml (new) - helm/values.yaml (added externalPrometheus config) - helm/values.schema.json (added schema definition)

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gemini-code-assist · 2026-03-04T10:38:21Z

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the vLLM Helm chart by introducing robust support for external Prometheus monitoring. It provides a new ServiceMonitor Helm template and corresponding configuration options, allowing users with existing Prometheus setups to seamlessly integrate vLLM metrics collection. This change significantly improves flexibility and reduces resource duplication for users who manage their own Prometheus instances, streamlining their monitoring infrastructure.

Highlights

External Prometheus Integration: Introduced a conditional Helm template for a Kubernetes ServiceMonitor resource, enabling external Prometheus instances to scrape vLLM metrics without deploying the bundled observability stack.
Configuration Options: Added a new externalPrometheus section in values.yaml and values.schema.json for detailed configuration of the ServiceMonitor, including namespace, labels, service selector, port, path, interval, and scrape timeout.
Backward Compatibility: The new external Prometheus integration feature is disabled by default, ensuring that existing deployments remain unaffected.

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Changelog

helm/templates/servicemonitor.yaml
- Added a new Helm template for a Kubernetes ServiceMonitor resource.
helm/values.schema.json
- Added a new externalPrometheus object to the schema, defining its properties and types.
helm/values.yaml
- Introduced the externalPrometheus configuration block with default values and comments.

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Copilot

Pull request overview

Adds Helm support for creating a ServiceMonitor when teams use an existing Prometheus Operator stack, so vLLM metrics can be scraped without installing the bundled observability components.

Changes:

Added new externalPrometheus configuration block in helm/values.yaml
Added JSON schema entries for externalPrometheus in helm/values.schema.json
Added a conditional helm/templates/servicemonitor.yaml to render a ServiceMonitor when externalPrometheus.enabled is set

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
helm/values.yaml	Introduces `externalPrometheus` configuration knobs (namespace, labels, selector, endpoint settings).
helm/values.schema.json	Adds schema definition for `externalPrometheus` values validation/tooling.
helm/templates/servicemonitor.yaml	Implements the conditional `ServiceMonitor` manifest for external Prometheus Operator setups.

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Copilot · 2026-03-04T10:43:14Z

helm/templates/servicemonitor.yaml

+    {{- else }}
+    matchLabels:
+      app.kubernetes.io/instance: {{ .Release.Name }}
+      app.kubernetes.io/managed-by: helm


The default spec.selector.matchLabels is broad enough to match the router and cache-server Services (they share app.kubernetes.io/instance and app.kubernetes.io/managed-by). Since those Services don’t expose a service-port port, this ServiceMonitor will create invalid/noisy targets by default. Consider tightening the default selector to only match serving-engine Services (e.g., include app.kubernetes.io/component: serving-engine), and rely on externalPrometheus.serviceSelector for other cases (router/cache).

Suggested change

app.kubernetes.io/managed-by: helm

app.kubernetes.io/managed-by: helm

app.kubernetes.io/component: serving-engine

Copilot · 2026-03-04T10:43:15Z

helm/templates/servicemonitor.yaml

+  {{- if .Values.externalPrometheus.namespace }}
+  namespaceSelector:
+    matchNames:
+      - {{ .Release.Namespace }}


This introduces new conditional rendering logic for an external ServiceMonitor, but there’s no corresponding Helm unittest coverage. Adding a small test case (enabled/disabled, namespaceSelector behavior, and default selector/portName rendering) would help prevent regressions.

Suggested change

- {{ .Release.Namespace }}

- {{ .Values.externalPrometheus.namespace }}

gemini-code-assist

Code Review

This pull request introduces a ServiceMonitor template for integrating with an external Prometheus, which is a valuable addition. The implementation is well-structured, providing flexibility through values.yaml. I've made a few suggestions in helm/templates/servicemonitor.yaml to improve the template's conciseness and maintainability by using common Helm templating patterns. Overall, the changes are solid.

gemini-code-assist · 2026-03-04T10:44:02Z

helm/templates/servicemonitor.yaml

+{{- if .Values.externalPrometheus }}
+{{- if .Values.externalPrometheus.enabled }}


For better readability and to make the template more concise, you can combine these two if statements into a single one using the and function. This is a common practice in Helm templates. You would also need to remove one of the {{- end }} statements at the end of the file (e.g., line 45).

{{- if and .Values.externalPrometheus .Values.externalPrometheus.enabled }}

gemini-code-assist · 2026-03-04T10:44:02Z

helm/templates/servicemonitor.yaml

+  {{- if .Values.externalPrometheus.namespace }}
+  namespace: {{ .Values.externalPrometheus.namespace }}
+  {{- else }}
+  namespace: {{ .Release.Namespace }}
+  {{- end }}


This if-else block for setting the namespace can be simplified using the default function. This makes the template more readable and concise.

namespace: {{ .Values.externalPrometheus.namespace | default .Release.Namespace }}

gemini-code-assist · 2026-03-04T10:44:02Z

helm/templates/servicemonitor.yaml

+      {{- if .Values.externalPrometheus.path }}
+      path: {{ .Values.externalPrometheus.path }}
+      {{- else }}
+      path: /metrics
+      {{- end }}


This if-else block can be simplified using the default function, which is consistent with how portName and interval are handled in this template. This improves readability and reduces verbosity.

path: {{ .Values.externalPrometheus.path | default "/metrics" }}

Copilot AI review requested due to automatic review settings March 4, 2026 10:37

Copilot started reviewing on behalf of NJX-njx March 4, 2026 10:38 View session

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brokedba mentioned this pull request Mar 4, 2026

feat(helm) add monitoring conf as a sub chart #860

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ruizhang0101 closed this Mar 31, 2026

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feat: add ServiceMonitor template for external Prometheus#866

feat: add ServiceMonitor template for external Prometheus#866
NJX-njx wants to merge 1 commit intovllm-project:mainfrom
NJX-njx:feat/606-servicemonitor-support

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	app.kubernetes.io/managed-by: helm
	app.kubernetes.io/managed-by: helm
	app.kubernetes.io/component: serving-engine

	- {{ .Release.Namespace }}
	- {{ .Values.externalPrometheus.namespace }}

		{{- if .Values.externalPrometheus }}
		{{- if .Values.externalPrometheus.enabled }}

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NJX-njx commented Mar 4, 2026

Summary

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