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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

  • You need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. If you do not already have a cluster, you can create one by using Minikube, or you can use one of these Kubernetes playgrounds:

To check the version, enter kubectl version.

Creating Redis deployment and service

  1. Create a Redis deployment:

    kubectl apply -f https://k8s.io/examples/application/guestbook/redis-master-deployment.yaml

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

    deployment.apps/redis-master created

    View the pod status to check that it is ready:

    kubectl get pods

    The output displays the pod created:

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

    View the deployment status:

    kubectl get deployment

    The output displays that the deployment was created:

    NAME         READY   UP-TO-DATE   AVAILABLE   AGE
redis-master 1/1     1            1           55s

    View the replicaset status using:

    kubectl get rs

    The output displays that the replicaset was created:

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

  2. Create a Redis service:

    kubectl apply -f https://k8s.io/examples/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

    The output displays the service created:

    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 pod name, to select a matching pod to port forward to since Kubernetes v1.10.

    kubectl port-forward redis-master-765d459796-258hz 7000:6379

    which is the same as

    kubectl port-forward pods/redis-master-765d459796-258hz 7000:6379

    or

    kubectl port-forward deployment/redis-master 7000:6379

    or

    kubectl port-forward rs/redis-master 7000:6379

    or

    kubectl port-forward svc/redis-master 7000:6379

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

    I0710 14:43:38.274550    3655 portforward.go:225] Forwarding from 127.0.0.1:7000 -> 6379
I0710 14:43:38.274797    3655 portforward.go:225] Forwarding from [::1]:7000 -> 6379

  2. Start the Redis command line interface:

    redis-cli -p 7000

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

    127.0.0.1:7000>ping

    A successful ping request returns PONG.

Discussion

Connections made to local port 7000 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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