Connecting To Prometheus

How do you connect to a running Prometheus server and open its UI? This guide explains common methods to access Prometheus deployed inside a Kubernetes cluster, how to inspect the Service that exposes it, and a quick demo using kubectl port-forward for local access. We’ll cover:

Inspecting the Prometheus Service
Options to expose Prometheus externally (NodePort, LoadBalancer, Ingress)
Quick demo: port-forwarding for local access

Inspect the Prometheus Service

First, list services to find Prometheus:

kubectl get service

Example output (filtered to Prometheus-related services):

NAME                                    TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)                      AGE
prometheus-grafana                      ClusterIP   10.100.235.247   <none>        80/TCP                       11h
prometheus-kube-prometheus-prometheus   ClusterIP   10.100.54.169    <none>        9090/TCP                     11h
prometheus-operated                     ClusterIP   None             <none>        9090/TCP                     11h
prometheus-prometheus-node-exporter     ClusterIP   10.100.248.61    <none>        9100/TCP                     11h

Here, prometheus-kube-prometheus-prometheus is type: ClusterIP, meaning it’s only reachable from inside the cluster (pods and other cluster-local clients). To export the full Service manifest for inspection:

kubectl get service prometheus-kube-prometheus-prometheus -o yaml > service.yaml

A relevant excerpt from that YAML:

apiVersion: v1
kind: Service
metadata:
  name: prometheus-kube-prometheus-prometheus
  labels:
    app.kubernetes.io/name: prometheus
    prometheus: prometheus-kube-prometheus-prometheus
spec:
  clusterIP: 10.100.54.169
  ports:
    - name: http-web
      port: 9090
      protocol: TCP
      targetPort: 9090
  selector:
    app.kubernetes.io/name: prometheus
    prometheus: prometheus-kube-prometheus-prometheus
  type: ClusterIP

Options to access Prometheus from outside the cluster

You have several ways to make Prometheus accessible externally:

Change the Service type:
- NodePort — exposes the Service on a node port accessible on each node.
- LoadBalancer — requests a cloud provider load balancer to route external traffic.
Create an Ingress that routes HTTP(S) to the Service.
Use kubectl port-forward for a short-lived local tunnel (great for demos and debugging).

Method	Best for	Notes
NodePort	Quick external access for testing	Simple to set up; exposes a port on every node; less flexible for production
LoadBalancer	Production external access in cloud environments	Provisioned by cloud provider; may incur costs
Ingress	HTTP(S) routing with hostnames and TLS	Recommended for multi-tenant or secure access; combine with auth and TLS
`kubectl port-forward`	Short-lived debugging or demos	Local-only, temporary, no external exposure

Quick commands to change the Service type to NodePort: Patch the Service (one-liner):

kubectl patch svc prometheus-kube-prometheus-prometheus \
  -p '{"spec": {"type": "NodePort"}}'

Or edit the Service manifest interactively:

kubectl edit svc prometheus-kube-prometheus-prometheus
# then change `type: ClusterIP` to `type: NodePort` and save

For production or multi-user access, prefer LoadBalancer (cloud) or an Ingress with authentication and TLS. NodePort is simple but less flexible for serving traffic securely at scale.

Quick demo — port-forward Prometheus to localhost

Port-forwarding is the fastest way to access the Prometheus UI from your laptop for verification or troubleshooting.

Find a Prometheus pod using labels:

kubectl get pods -l app.kubernetes.io/name=prometheus

Forward port 9090 from the Service or a specific pod to your local machine:

Forward the Service (recommended — will route to the pod backing the Service):

kubectl port-forward svc/prometheus-kube-prometheus-prometheus 9090:9090

Or forward a specific Prometheus pod:

kubectl port-forward pod/<prometheus-pod-name> 9090:9090

Open the Prometheus UI in your browser:

http://localhost:9090 This creates a temporary tunnel from your local port 9090 into the cluster’s Prometheus server and is ideal for quick checks or running queries.

kubectl port-forward is temporary and only binds to your client machine. It is not a replacement for proper external access (NodePort/LoadBalancer/Ingress) in production.

A browser screenshot of the Prometheus monitoring UI showing a query input bar, Graph/Table tabs, and a blank result area that says "No data queried yet." The toolbar shows options like Enable autocomplete, an Execute button, and an "Add Panel" button.

Summary

A Service of type: ClusterIP is cluster-internal only.
For quick access use kubectl port-forward.
For sustained or production access prefer LoadBalancer or Ingress with TLS and authentication; NodePort is a simple alternative for non-production use.

Links and References

Prometheus: https://prometheus.io/docs/introduction/overview/
Kubernetes: https://kubernetes.io/docs/concepts/overview/what-is-kubernetes/
Services (Kubernetes): https://kubernetes.io/docs/concepts/services-networking/service/
Port forwarding (kubectl): https://kubernetes.io/docs/tasks/access-application-cluster/port-forward-access-application/
Ingress (Kubernetes): https://kubernetes.io/docs/concepts/services-networking/ingress/

Introduction

Observability Fundamentals

Prometheus Fundamentals

PromQL

Dashboarding & Visualization

Application Instrumentation

Service Discovery

Push Gateway

Alerting

Monitoring Kubernetes

Conclusion

Scaling & Long Term Storage

Connecting To Prometheus

Inspect the Prometheus Service

Options to access Prometheus from outside the cluster

Quick demo — port-forward Prometheus to localhost

Summary

Links and References

Watch Video

​Inspect the Prometheus Service

​Options to access Prometheus from outside the cluster

​Quick demo — port-forward Prometheus to localhost

​Summary

​Links and References

Watch Video

Inspect the Prometheus Service

Options to access Prometheus from outside the cluster

Quick demo — port-forward Prometheus to localhost

Summary

Links and References