Move cluster image loading logic into Deployer

[nkubala]

Related: #6117, #6107

Description

The Runner has historically been responsible for loading images into local kubernetes clusters before running, as is required by kind, k3d, and even minikube (when running with containerd). However, this is really a behavior that should be carried out by the Deployer, as it is the component that has knowledge of the cluster - the Runner is just an orchestrator.

This change creates an ImageLoader component, which is responsible for performing any image loading into the cluster before doing a deploy.

This component has a single method on it:

type ImageLoader interface {
  LoadImages(context.Context, io.Writer, images []graph.Artifact)
}

A single implementation of this interface is added in the pkg/skaffold/kubernetes/loader package, which embeds the existing image load logic from the Runner inside of it.

One method is added to the Deployer interface to give the Runner the ability to pass images it has marked as local:

type Deployer interface {
  ...

  RegisterLocalImages([]graph.Artifact)
}

---

Update: Each Deployer is now responsible for loading the set of images that it will be deploying, similar to the way each Deployer only tracks its own images for logging. This is determined by the union of the following 3 sets:

• Images which have been deemed by the Runner as local
• Images which have been found in a Deployer's set of manifests
• Images which are passed by the Deployer to be loaded

[codecov]

Codecov Report

Merging #6124 (3b44ece) into master (fe12a8a) will decrease coverage by 0.02%.
The diff coverage is 61.53%.

@@            Coverage Diff             @@
##           master    #6124      +/-   ##
==========================================
- Coverage   69.96%   69.94%   -0.03%     
==========================================
  Files         477      481       +4     
  Lines       18283    18336      +53     
==========================================
+ Hits        12792    12825      +33     
- Misses       4545     4560      +15     
- Partials      946      951       +5     

Impacted Files	Coverage Δ
pkg/skaffold/deploy/deploy_mux.go	53.44% <0.00%> (-0.94%)	⬇️
pkg/skaffold/deploy/kubectl/cli.go	88.09% <ø> (ø)
pkg/skaffold/loader/loader_mux.go	0.00% <0.00%> (ø)
pkg/skaffold/runner/v1/apply.go	0.00% <0.00%> (ø)
pkg/skaffold/deploy/helm/deploy.go	77.25% <42.85%> (-0.98%)	⬇️
pkg/skaffold/deploy/kpt/kpt.go	79.93% <42.85%> (-0.93%)	⬇️
pkg/skaffold/deploy/kustomize/kustomize.go	72.95% <42.85%> (-1.39%)	⬇️
pkg/skaffold/loader/provider.go	42.85% <42.85%> (ø)
pkg/skaffold/loader/loader.go	50.00% <50.00%> (ø)
pkg/skaffold/kubernetes/loader/load.go	66.15% <66.15%> (ø)
... and 13 more

---

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[gsquared94]

I tried this on examples/microservices and examples/multi-config-microservices with the default kind cluster but the image load doesn't happen correctky.

Loading images into kind cluster nodes...
Images loaded in 588ns
Loading images into kind cluster nodes...
Images loaded in 181ns
Starting deploy...
 - service/leeroy-app created
 - deployment.apps/leeroy-app created
 - deployment.apps/leeroy-web created
Waiting for deployments to stabilize...
 - deployment/leeroy-app: Unschedulable: 0/1 nodes available: 1 node is not ready
    - pod/leeroy-app-cd547645c-dcmrw: Unschedulable: 0/1 nodes available: 1 node is not ready
 - deployment/leeroy-web: Unschedulable: 0/1 nodes available: 1 node is not ready
    - pod/leeroy-web-77b44f4bc4-wvv98: Unschedulable: 0/1 nodes available: 1 node is not ready
 - deployment/leeroy-app: container leeroy-app is waiting to start: leeroy-app:49e54603b1b22ca355856617f5a8138de3c355492ee6752b26a0ed6ccc3cb51d can't be pulled
    - pod/leeroy-app-cd547645c-dcmrw: container leeroy-app is waiting to start: leeroy-app:49e54603b1b22ca355856617f5a8138de3c355492ee6752b26a0ed6ccc3cb51d can't be pulled
 - deployment/leeroy-app failed. Error: container leeroy-app is waiting to start: leeroy-app:49e54603b1b22ca355856617f5a8138de3c355492ee6752b26a0ed6ccc3cb51d can't be pulled.
Cleaning up...
 - service "leeroy-app" deleted
 - deployment.apps "leeroy-app" deleted
 - deployment.apps "leeroy-web" deleted
2/2 deployment(s) failed

[gsquared94]

also, the image load is happening multiple times in a single dev loop for multiple deployers (or multi config)

Loading images into kind cluster nodes...
Images loaded in 588ns
Loading images into kind cluster nodes...
Images loaded in 181ns

[gsquared94]

lgtm. An alternative approach probably could be to modify graph.Artifact to directly have a field isLocal when the Builder returns the result and do away with RegisterLocalImages method on the Deployer.