Support static files/interpreted language containers

[dgageot]

Containers that serve static resources such as html, css or javascript shouldn't be built each time there's a change. It's too painful for the users.

With Docker for Desktop and docker-compose, I’d just bind mount the sources and that would be it. No rebuild involved and Live Reload could be setup to smooth the developer experience even more.
What we could do in Skaffold, un dev mode, is let the user bind mount the sources into the container running on the local Kubernetes. That’s not trivial because:

• The user would have to know what they are doing.
• Skaffold should at least make it possible to disable rebuild on some artifacts.
• The bind mounting should be configured in the skaffold.yaml and injected into the kubectl manifests (do we know how to do that?)
• Or we should support deploying a different list of manifests in dev mode and in run mode: one with the bind mounting (dev) and one without it (run).

Once we have that, we can also think about Live Reload.

[dgageot]

I've run some tests on platforms that support sharing files with the host: Docker for Desktop and minikube.

Let's say I'm developing a static website that runs with nginx. My original k8s manifest is:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx
spec:
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: web
        image: nginx

We could have some kind of configuration at the artifact level in the skaffold.yaml:

apiVersion: skaffold/v1alpha2
kind: Config
build:
  artifacts:
  - imageName: gcr.io/k8s-skaffold/skaffold-example
     watchChanges: false
     mount: ./html:/usr/share/nginx/html
deploy:
  kubectl:
    manifests:
      - k8s-*

On Docker for Desktop, Skaffold could then patch the yaml:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx
spec:
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: web
        image: nginx
        volumeMounts:
        - mountPath: /usr/share/nginx/html
          name: html
      volumes:
      - name: html
        hostPath:
          path: /Users/dgageot/[...]/html

On minikube, Skaffold could patch a different way:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx
spec:
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: web
        image: nginx
        volumeMounts:
        - mountPath: /usr/share/nginx/html
          name: html
      volumes:
      - name: html
        hostPath:
          path: /skaffold/mount1

and make sure this command runs: minikube mount /Users/dgageot/[...]/html:/skaffold/mount1

[dgageot]

@r2d4 @dlorenc @viglesiasce Do you think I should try and implement something along those lines?

[jonjohnsonjr]

Could you use the same heuristic as in #565 to skip building these?

[bhack]

What do you think of the ksync approach?

[richardscarrott]

@dgageot this feature would make using Skaffold for containers running TypeScript or Babel on NodeJS a great option, I wondered whether you’ve been able to make any progress on this at all?

[r2d4]

Removing @dgageot and @nkubala since I have a prototype of this that I'm planning to add

[balopat]

closing this as #1039 fixed it.