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Use Port Forwarding to Access Applications in a Cluster

This page shows how to use kubectl port-forward to connect to a Redis server running in a Kubernetes cluster. This type of connection can be useful for database debugging.

Before you begin

To check the version, enter kubectl version.

Creating Redis deployment and service

  1. Create a Redis deployment:

    kubectl create -f https://k8s.io/docs/tutorials/stateless-application/guestbook/redis-master-deployment.yaml

    The output of a successful command verifies that the deployment was created:

    deployment "redis-master" created

    When the pod is ready, you can get:

    kubectl get pods

    NAME                            READY     STATUS    RESTARTS   AGE
redis-master-765d459796-258hz   1/1       Running   0          50s

    kubectl get deployment

    NAME         DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
redis-master 1         1         1            1           55s

    kubectl get rs

    NAME                      DESIRED   CURRENT   READY     AGE
redis-master-765d459796   1         1         1         1m

  2. Create a Redis service:

    kubectl create -f https://k8s.io/docs/tutorials/stateless-application/guestbook/redis-master-service.yaml

    The output of a successful command verifies that the service was created:

    service "redis-master" created

    Check the service created:

    kubectl get svc | grep redis

    NAME           TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)    AGE
redis-master   ClusterIP   10.0.0.213   <none>        6379/TCP   27s

  3. Verify that the Redis server is running in the pod and listening on port 6379:

    kubectl get pods redis-master-765d459796-258hz –template=‘{{(index (index .spec.containers 0).ports 0).containerPort}}{{”\n”}}’

    The output displays the port:

    6379

Forward a local port to a port on the pod

  1. kubectl port-forward allows using resource name, such as a service name, to select a matching pod to port forward to since Kubernetes v1.10.

    kubectl port-forward redis-master-765d459796-258hz 6379:6379

    which is the same as

    kubectl port-forward pods/redis-master-765d459796-258hz 6379:6379

    or

    kubectl port-forward deployment/redis-master 6379:6379

    or

    kubectl port-forward rs/redis-master 6379:6379

    or

    kubectl port-forward svc/redis-master 6379:6379

    Any of the above commands works. The output is similar to this:

    I0710 14:43:38.274550    3655 portforward.go:225] Forwarding from 127.0.0.1:6379 -> 6379
I0710 14:43:38.274797    3655 portforward.go:225] Forwarding from [::1]:6379 -> 6379

  2. Start the Redis command line interface:

    redis-cli

  3. At the Redis command line prompt, enter the ping command:

    127.0.0.1:6379>ping

    A successful ping request returns PONG.

Discussion

Connections made to local port 6379 are forwarded to port 6379 of the pod that is running the Redis server. With this connection in place you can use your local workstation to debug the database that is running in the pod.

Warning: Due to known limitations, port forward today only works for TCP protocol. The support to UDP protocol is being tracked in issue 47862.

What's next

Learn more about kubectl port-forward.

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