Kubernetes do not support publish all exposed ports to random ports

[gyliu513]

Is this a request for help? (If yes, you should use our troubleshooting guide and community support channels, see http://kubernetes.io/docs/troubleshooting/.):

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Is this a BUG REPORT or FEATURE REQUEST? (choose one):

Kubernetes version (use kubectl version):
master

Environment:

• Cloud provider or hardware configuration:
• OS (e.g. from /etc/os-release):
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What happened:
Currently in Kubernetes, if I want to enable the docker host port mapping, I have to write the hostPort explicitly in the yaml template and kubernetes cannot publish the host ports to random ports like docker does in docker run -P.

    ports:
    - containerPort: 2381
      hostPort: 2381
      name: serverport
      protocol: TCP
    - containerPort: 4002
      hostPort: 4002
      name: clientport
      protocol: TCP

This is not convenient for some customers who want to use docker's port mapping feature as the end user need to set the hostPort by themselves and this may cause some port conflict especially when scale up a pod on same node. Yes, we can workaround the scale up issue with pod anti affinity feature, but it is not convenient to let end user write those hostPorts for a large deployment with many exposed hostPort.

What you expected to happen:

How to reproduce it (as minimally and precisely as possible):

Anything else we need to know:

[gyliu513]

For the Kubernetes native NodePort, the problem is that the customer only want to access the specified pod with node IP (where the pod is running) + host port mapping as they already have a haproxy outside the Kubernetes cluster and they do not want the NodePort load balance as it may access pods in other nodes.

[gyliu513]

After some discussion in sig-network, there are also some people have the similar requirement of want an external load balancer to communicate with pod directly, instead of passing through nodePort/clusterIP. Currently they can only specify different hostPort to different deployments. Letting kubernetes to automatically assign hostPort for different deployment (or maybe service?) will be quite useful.

[gyliu513]

/sig network

[gyliu513]

Close this one and trace it in #40131