go-dumbcri

README

Go Dumb CRI

The dumb container runtime trying to be compatible with Kubernetes CRI.

Usage

Run the server and create an IPC socket in /tmp/go-dumbcri.sock

go run .

Install crictl and use it as the client

brew install cri-tools
crictl --runtime-endpoint unix:///tmp/go-dumbcri.sock version

The output should look like this

Version:  v1alpha2
RuntimeName:  go-dumbcri
RuntimeVersion:  v0.0.0-alpha.1
RuntimeApiVersion:  v0.0.0-alpha.1

Why

go-dumbcri is a small project to learn about the internals of Kubernetes CRI.

Lessons Learned

What I have understood so far is that the container runtime interface is defined in protobuf in https://github.com/kubernetes/kubernetes/tree/v1.22.3/staging/src/k8s.io/cri-api.

The code is extracted into a dedicated repository at https://github.com/kubernetes/cri-api/tree/v0.22.3. Or maybe the other way around...

It is then imported to implement either a client ( https://github.com/kubernetes-sigs/cri-tools/blob/ed2adf0/go.mod#L27 ) or a server ( https://github.com/containerd/containerd/blob/d418660/go.mod#L75, https://github.com/cri-o/cri-o/blob/3943334/go.mod#L70 ).

Documentation

• https://github.com/kubernetes/cri-api
• https://kubernetes.io/blog/2016/12/container-runtime-interface-cri-in-kubernetes/
• https://kubernetes.io/docs/setup/production-environment/container-runtimes/