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
- Creating Redis deployment and service
- Forward a local port to a port on the Pod
- Discussion
- What's next
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
Create a Deployment that runs Redis:
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’s 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
The Deployment automatically manages a ReplicaSet. View the ReplicaSet status using:
kubectl get replicaset
The output displays that the ReplicaSet was created:
NAME DESIRED CURRENT READY AGE redis-master-765d459796 1 1 1 1m
Create a Service to expose Redis on the network:
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 service redis-master
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
Verify that the Redis server is running in the Pod, and listening on port 6379:
# Change redis-master-765d459796-258hz to the name of the Pod 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:
6379
(this is the TCP port allocated to Redis on the internet).
Forward a local port to a port on the Pod
kubectl port-forward
allows using resource name, such as a pod name, to select a matching pod to port forward to.# Change redis-master-765d459796-258hz to the name of the Pod 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 replicaset/redis-master 7000:6379
or
kubectl port-forward service/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
Start the Redis command line interface:
redis-cli -p 7000
At the Redis command line prompt, enter the
ping
command: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.
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.
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