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:

    Your Kubernetes server must be at or later than version v1.10. To check the version, enter kubectl version.

  • Install redis-cli.

Creating Redis deployment and service

  1. Create a Deployment that runs Redis:

    1. 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:

    1. deployment.apps/redis-master created

    View the pod status to check that it is ready:

    1. kubectl get pods

    The output displays the pod created:

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

    View the Deployment’s status:

    1. kubectl get deployment

    The output displays that the Deployment was created:

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

    The Deployment automatically manages a ReplicaSet. View the ReplicaSet status using:

    1. kubectl get replicaset

    The output displays that the ReplicaSet was created:

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

  2. Create a Service to expose Redis on the network:

    1. 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:

    1. service/redis-master created

    Check the Service created:

    1. kubectl get service redis-master

    The output displays the service created:

    1. NAME           TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)    AGE
    2. 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:

    1. # Change redis-master-765d459796-258hz to the name of the Pod
    2. kubectl get pod redis-master-765d459796-258hz --template='{{(index (index .spec.containers 0).ports 0).containerPort}}{{"\n"}}'

    The output displays the port for Redis in that Pod:

    1. 6379

    (this is the TCP port allocated to Redis on the internet).

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.

    1. # Change redis-master-765d459796-258hz to the name of the Pod
    2. kubectl port-forward redis-master-765d459796-258hz 7000:6379

    which is the same as

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

    or

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

    or

    1. kubectl port-forward replicaset/redis-master 7000:6379

    or

    1. kubectl port-forward service/redis-master 7000:redis

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

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

  2. Start the Redis command line interface:

    1. redis-cli -p 7000

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

    1. ping

    A successful ping request returns:

    1. 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.

Note: kubectl port-forward is implemented for TCP ports only. The support for UDP protocol is tracked in issue 47862.

What’s next

Learn more about kubectl port-forward.