Kubernetes (K8s) + Kubectl Port-Forward: A Comprehensive Guide (2023)
The Kubernetes command-line tool, kubectl, allows you to run commands against Kubernetes clusters. We can use kubectl to deploy applications, inspect and manage cluster resources, and view logs. For more information including a complete list of kubectl operations.
As per my knowledge to access something inside the cluster, there ae a couple of different options available to,
- Cluster IP service with Ingress-Nginx
- NodePort Service to expose the pod directly to the outside world.
Above both approach will require to write config file.
Note: In case if you want to access a pod without writing a config file then it comes to 3rd option (kubectl port-forward).
- Port Forward: We can run a command at our terminal that tells our Kubernets (k8) cluster to port-forward a port off a very specific pod inside of our cluster when we use this port forwarding thing that’s going to cause our cluster to essentially behaves as though it has a node port service running inside it. It’s going to expose this pod or a very specific port on it to the outside world and allow us to connect to it directly from our local machine. In this article we will discuss on 3rd option I mean Port Forward. Remember following important points during microservices implementation.
- kubectl exposes commands that can be used to create a Service for an application and assigns an IP address to access it from internet.
- As far as I understand, to access any application within Kubernetes cluster there should be a Service resource created and that should have an IP address which is accessible from an external network.
- But in case of port-forward how does kubectl create a connection to the application without an IP address which is accessible externally?
- As per understanding in Kubernetes, every pod gets its own ip address from 10.*, that is usable only within the cluster right. Now, the port-forward feature of kubectl simply tunnels the traffic from a specified port at your local host machine to the specified port on the specified pod. API server then becomes, in a sense, a temporary gateway between your local port and the Kubernetes cluster.
- kubectl port-forward forwards connections to a local port to a port on a pod. Compared to kubectl proxy, kubectl port-forward is more generic as it can forward TCP traffic while kubectl proxy can only forward HTTP traffic.
- kubectl port-forward is useful for testing/debugging purposes so you can access your service locally without exposing it.
kubectl port-forward <pod-name> <locahost-port>:<pod-port> --address='0.0. 0.0'
Where –address=’0.0.0.0′ is mainly to make users can access Kubernetes cluster from another server.
Usage examples:
- Listen on port 8888 locally, forwarding to 5000 in the pod
kubectl port-forward pod/mypod 8888:5000
- Listen on port 8888 on all addresses, forwarding to 5000 in the pod
kubectl port-forward --address 0.0.0.0 pod/mypod 8888:5000
- Listen on a random port locally, forwarding to 5000 in the pod
kubectl port-forward pod/mypod :5000
- Listen on port 8888 on localhost and selected IP, forwarding to 5000 in the pod
kubectl port-forward --address localhost,10.19.21.23 pod/mypod 8888:5000
- Listen on ports 5000 and 6000 locally, forwarding data to/from ports 5000 and 6000 in the pod
kubectl port-forward pod/mypod 5000 6000
- Listen on ports 5000 and 6000 locally, forwarding data to/from ports 5000 and 6000 in a pod selected by the deployment
kubectl port-forward deployment/mydeployment 5000 6000
- Listen on ports 5000 and 6000 locally, forwarding data to/from ports 5000 and 6000 in a pod selected by the service
kubectl port-forward service/myservice 5000 6000
Happy learning 🙂