Host node address (alias or static ip?) from inside containers-CodePudding

What is the correct way to address a host node from inside containers?

I have a container that resides on a host node, and the host node has a web server running on it. The container needs to be able to hit web server on the host node.

I expected to find an alias for the host node like node..cluster.local (10.1.111.192), but I can't find it in the documentation.

The environment is microk8s with kubedns enabled.

The address assigned to the host on the calico interface is accessible from inside the node: 10.1.111.192 and I found in the documentation that I can add a hostalias-pod, so I could add the alias, eg. node.local (10.1.111.192). https://kubernetes.io/docs/tasks/network/customize-hosts-file-for-pods/

Hardcoding the IP doesn't seem graceful, but I'm in a single-node environment, so it's not likely to matter if the node address doesn't change (does this ever change?). This is a small project where I'm trying to learn though, so I wanted to find the most correct way to do this.

CodePudding user response：

You can use the downward API to get the underlying hostname, worth to mention that it will return the IP of the node where the pod is running on.

      env:
        - name: HOST_IP
          valueFrom:
            fieldRef:
              fieldPath: status.hostIP

so from inside pod, you will be able to reach that particular host

curl $HOST_IP:8080

A complete example

apiVersion: v1
kind: Pod
metadata:
  name: print-host-ip
spec:
  containers:
    - name: print-host-ip
      image: gcr.io/google_containers/busybox
      env:
        - name: HOST_IP
          valueFrom:
            fieldRef:
              fieldPath: status.hostIP
      command: [ "/bin/sh", "-c", 'echo "host ip is $HOST_IP"' ]