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In this guide, you’ll learn how to connect to a Prometheus server and access its web UI. We’ll cover several methods, starting with inspecting the Prometheus service using kubectl.

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Listing Cluster Services

Begin by listing all services in your Kubernetes cluster to locate the Prometheus service: 
kubectl get service
An example output might look similar to: 
NAME                                        TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)                         AGE
alertmanager-operated                       ClusterIP   None            <none>        9093/TCP,9094/TCP,9094/UDP         4d5h
kubernetes                                  ClusterIP   10.100.0.1      <none>        443/TCP                         11h
prometheus-grafana                          ClusterIP   10.100.235.247  <none>        80/TCP                          11h
prometheus-kube-prometheus-alertmanager      ClusterIP   10.100.53.114   <none>        9093/TCP                        11h
prometheus-kube-prometheus-operator           ClusterIP   10.100.196.32   <none>        443/TCP                         11h
prometheus-kube-state-metrics                 ClusterIP   10.100.54.169   <none>        9090/TCP                        11h
prometheus-operated                         ClusterIP   10.100.133.149  <none>        8080/TCP                        11h
prometheus-prometheus-node-exporter         ClusterIP   10.100.248.61   <none>        9100/TCP                        11h
This output confirms that the Prometheus service is running. Notice that the service is of type ClusterIP, meaning it is accessible only within the cluster.

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Inspecting the Prometheus Service Configuration

To investigate further, output the service configuration to a YAML file. For instance, execute: 
kubectl get service prometheus-kube-prometheus-prometheus -o yaml > service.yaml
Opening the YAML file, you will notice it is configured as a ClusterIP service. Below is an excerpt of key metadata sections: 
apiVersion: v1
kind: Service
metadata:
  annotations:
    meta.helm.sh/release-name: prometheus
    meta.helm.sh/release-namespace: default
    creationTimestamp: "2022-11-21T18:23:09Z"
  labels:
    app: kube-prometheus-stack-prometheus
    app.kubernetes.io/instance: prometheus
    app.kubernetes.io/managed-by: Helm
    app.kubernetes.io/part-of: kube-prometheus-stack
    app.kubernetes.io/version: 41.9.1
    chart: kube-prometheus-stack-41.9.1
    heritage: Helm
And the corresponding service specifications that confirm the ClusterIP setup: 
resourceVersion: "801692"
spec:
  clusterIP: 10.100.54.169
  clusterIPs:
    - 10.100.54.169
  internalTrafficPolicy: Cluster
  ipFamilies:
    - IPv4
  ipFamilyPolicy: SingleStack
  ports:
    - name: http-web
      port: 9090
      protocol: TCP
      targetPort: 9090
  selector:
    app.kubernetes.io/name: prometheus
    prometheus: prometheus-kube-prometheus-prometheus
  sessionAffinity: None
  type: ClusterIP
status:
  loadBalancer: {}
Since the service uses ClusterIP, it is only accessible from within your Kubernetes cluster.

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Enabling External Access

To access Prometheus externally, consider the following options:
  • Change the service type to NodePort or LoadBalancer.
  • Set up an Ingress resource to route traffic from a specific URL or domain to the Prometheus service.
For demo purposes, we’ll use port forwarding.

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Accessing Prometheus via Port Forwarding

First, check the running pods in your cluster: 
kubectl get pod
Once you have identified the correct Prometheus pod (for example, prometheus-prometheus-kube-prometheus-0), forward the pod’s port 9090 to your local machine: 
kubectl port-forward prometheus-prometheus-kube-prometheus-0 9090
With port forwarding active, open your browser and navigate to http://localhost:9090 to access the Prometheus web UI. This confirms that Prometheus is actively running.
Port forwarding is ideal for demos and testing. For production environments, switch to NodePort, LoadBalancer, or configure an Ingress for secure and stable external access.
By following these steps, you can effectively connect to your Prometheus server and access its UI for monitoring and troubleshooting. For further reading and advanced configurations, consider exploring the Kubernetes Documentation and Prometheus Documentation.

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