How are the docker port and Service and Pod ports related

RahulRege · July 2019

Hello everyone, this is my first post as I recently started LFD259 and at the Pod and Service creation exercise. I have worked with docker before, so trying to map how things are connected.

When I create the Pod, I do not see the ports on the Node2 getting created in the sudo docker ps -a. I then added a Service on top of it as well as added the NodePort. I can reach to my service just fine but I do not see any networking on my docker container.

I imagine the CNI plugin is doing the magic but wondering if anyone can shed some light or would reviewing the CNI documentation (it was mentioned as a resource in the lab) would be the way to go .

Thanks
Rahul

chrispokorni · July 2019

Hi @RahulRege,

When in doubt, it always helps to check the documentation

The pod is a wrapper around one or many containers and it creates a network namespace for its container(s) to share.

A pod created with a container is not exposed to the outside world. It is only accessible from the local node so you won't find a port on the local node, but you will be able to access your containerized application thru the pod's IP address.

As opposed to a single container exposed to the outside world thru a random high-port of the local node, a pod is exposed thru another Kubernetes resource - a Service. Specific types of services receive a random high-port on every node in the Kubernetes cluster (the same high-port number reserved on every node), allowing access to a single pod from any node in the cluster and from the outside world.

Regards,
-Chris

RahulRege · July 2019

Thanks Chris, that answers it.

How are the docker port and Service and Pod ports related

Best Answer

Answers

Categories

Upcoming Training

Kubernetes Administration (LFS458)

Linux System Administration (LFS301)

Open Source Virtualization (LFS462)

Linux Kernel Debugging and Security (LFD440)