Define build strategy with Kubernetes

[surajssd]

Kubernetes by default has no container image build mechanism, so what are the ways are we gonna support it?

[surajssd]

One point I would like to add here is the builds should be generic enough that image format is supported for both container runtimes that kubernetes supports i.e. docker and rkt

[sebgoa]

you want to run kompose within a k8s cluster ?

I am not sure I get it. It is a client side tool.

[kadel]

Hmm, I'm not sure I get it either.

Only way how to do builds with Kubernetes that I can think of right now is to build image (similarly as docker-compose would) and than push it to some registry that is also accessible by targeted Kubernetes cluster.

[surajssd]

I created this issue if we wanna give a end-to-end feel on k8s we will have to decide what we do with builds, are we gonna handle image builds for user? or right now keeping it out of our scope and giving user a warning and asking them to build themselves?

Our target users are gonna be developers who use kompose + k8s running locally in minikube like env, so how are we gonna handle this?

I want views of all of you folks.

[sebgoa]

ok got it.

IMHO for now we should skip "builds" and define it as "unsupported".

Because for images to be used within a k8s cluster they would need to be uploaded to a registry as well. So it will be difficult to run out of the box with kompose. There will be manual intervention not matter what.

[surajssd]

thanks for making this clear, will wait for what @janetkuo and @ngtuna has to say then we can close this issue! :)

[janetkuo]

I agree with @Runseb 😃

[ngtuna]

I'm +1 for @Runseb

[janetkuo]

Just to be clear, I also agree with @surajssd that we should give an end-to-end feel and should support "builds" in the future.

We can push to a registry specified in a preference file. K8s provides private Docker registry addon that we can use.

[rtnpro]

With support for openshift buildconfig implemented, we are now in a position to complete the end-to-end build story by supporting local builds for kubernetes and openshift.

Below, I am documenting the local build feature.

Goal

To support build directive in a Docker Compose service for Kubernetes (and hence Openshift) by building images locally and pushing it to a registry.

Issue

Kubernetes has a registry addon to host container images privately, but it does not have a mechanism like Openshift's buildconfig to internally build images from source in an automated way and push it to the internal registry. As a result, a kompose user trying to convert a compose file with a build directive and deploy it to kubernetes will need to do the following:

• build the image locally
• push it to a registry in use by the kubernetes setup
• may need to tinker with the image names in the artifacts generated by kompose

In order to provide a good user experience to Kubernetes Kompose users, we need to automate local image build, image upload to Kuberenetes (or Openshift) accessible registry. This will also prove to be useful for Openshift as well by allowing Kompose users (developers) to deploy local code without pushing it to a public repository.

Proposed solution

• Use system's docker command to build image locally
• Use service name as image name, or use service's metadata to override it
• Pushing image to remote registry:
  • Use docker push CLI to push image
  • You can push push to a non default registry by specifying it using CLI option --target-registry
  • Kompose will not take care of logging in to remote registry. The user needs to ensure that Docker is setup/configured to push to the target registry. Refer to 1
• Use built image's name in deployment artifacts as needed, so that the user does not need to edit them manually.

[pradeepto]

@rtnpro Thank you for the proposal.
I have one question though - one of the tenet of Kompose is that the user doesn't need docker engine / CLI installed / running. This proposal assumes that Docker engine / CLI is installed and running. Is that correct?

To be clear, I am NOT against the proposal. In fact, I would like to see this done and will highly appreciate the end-to-end feature in Kompose. But just wanted to bring this though to the table so that we know what we are changing.

Looks good otherwise but I would appreciate other folks who are more knowledgeable than me.