Moving docs from /vX to /docs; we will use branches for old versions.

docs/user-guide/connecting-to-applications-port-forward.md

@@ -0,0 +1,46 @@
+---
+---
+
+kubectl port-forward forwards connections to a local port to a port on a pod. Its man page is available [here](/docs/user-guide/kubectl/kubectl_port-forward). Compared to [kubectl proxy](/docs/user-guide/accessing-the-cluster/#using-kubectl-proxy), `kubectl port-forward` is more generic as it can forward TCP traffic while `kubectl proxy` can only forward HTTP traffic. This guide demonstrates how to use `kubectl port-forward` to connect to a Redis database, which may be useful for database debugging.
+
+## Creating a Redis master
+
+```shell
+$ kubectl create examples/redis/redis-master.yaml
+pods/redis-master
+```
+
+wait until the Redis master pod is Running and Ready,
+
+```shell
+$ kubectl get pods
+NAME           READY     STATUS    RESTARTS   AGE
+redis-master   2/2       Running   0          41s
+```
+
+## Connecting to the Redis master[a]
+
+The Redis master is listening on port 6397, to verify this,
+
+```shell
+$ kubectl get pods redis-master -t='{{(index (index .spec.containers 0).ports 0).containerPort}}{{"\n"}}'
+6379
+```
+
+then we forward the port 6379 on the local workstation to the port 6379 of pod redis-master,
+
+```shell
+$ kubectl port-forward redis-master 6379:6379
+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
+```
+
+To verify the connection is successful, we run a redis-cli on the local workstation,
+
+```shell
+$ redis-cli
+127.0.0.1:6379> ping
+PONG
+```
+
+Now one can debug the database from the local workstation.