skaffold render should accept tagged images

[yuwenma]

Expected behavior

skaffold render should be able to update the new tag to the image.

For example, if the old tag is 2020-09-28_0000 and the new tag is 2020-09-28_1111 , this change should happen in deployment.yaml files.

Actual behavior

Skaffold does not update but attach the new tag (See here). This results in an increasing image tag and eventually hits the max length limitation.

Information

• Skaffold version: v1.14
• Operating system: linux
• Contents of skaffold.yaml:

apiVersion: skaffold/v2beta7
kind: Config
build:
  artifacts:
  - image: skaffold-example
deploy:
  kubectl:
    manifests:
      - k8s-*

Steps to reproduce the behavior

1. Run "skaffold render", get the full image url from the stdout.
2. Replace the full image url with the pod.yaml "image" field.
3. Run "skaffold render" again.

pod.yaml

apiVersion: v1
kind: Pod
metadata:
  name: getting-started
spec:
  containers:
  - name: getting-started
    image: skaffold-example

Proposal

Per offline discussion w/ @nkubala , we expect skaffold render to accept a new flag "--ignoreTag=". When enabled, "skaffold render" will replace the image tag with the new tag instead of appending the tag at the image tail.

[nkubala]

the reason we designed skaffold this way is so users wouldn't get themselves into an unpredictable situation when deploying with skaffold. if a user provided a manifest with an existing tag and ran skaffold run, skaffold might build and deploy a different image than the one they expected (with the provided tag before running), which could produce some unexpected and potentially dangerous results (e.g. deploying to prod).

technically speaking this is possible in skaffold, but we should make sure we don't enable users to do things they don't mean to do, and that the UX is intuitive. --ignore-tags should probably be an all-or-nothing flag (i.e. you can't pass a specific flag you want to ignore - either ignore all, or replace all). we'd also probably want to at the very least issue a warning or something clear to the user that any previously built images with skaffold are not being used by the deployment if that flag is provided. what happens if --build-artifacts is provided? does the provided tag on the image take precedence, or the one built by skaffold?

we should also consider how this factors into a few other FRs related to render/deploy:

• deploying previously rendered results (Accept render output in skaffold deploy #4856), since this would need to skip the build/tag replacement of the rendered manifests, and just deploy them as is
• deploying untagged/unbuilt resources (deploy profile without build artifacts failing with "no tag provided for image" #3559), since this would require the deployer to stop validating build artifacts against deploy resources

[tejal29]

This issue is approaching SLO. Any takers @marlon-gamez @nkubala @yuwenma @gsquared94 @IsaacPD

[IsaacPD]

I'll try and get a fix available

[IsaacPD]

I have not actually been able to reproduce the behavior as described here. I tried it on the examples/getting-started project

1. skaffold render
   -- Outputs gcr.io/isaacpd-test/skaffold-example:1277ddcd3b1e840c76abe71d1d35fd1716a0cb87be41fa145a3e12ec0f2e2eb8 for the image name
2. Copy the output for the image name into k8s-pod.yaml

containers: 
- name: getting-started 
  image: gcr.io/isaacpd-test/skaffold-example:1277ddcd3b1e840c76abe71d1d35fd1716a0cb87be41fa145a3e12ec0f2e2eb8

3. skaffold render again

All that I see in the output is the same image name that was output as the original "skaffold render". I'm not getting the scenario where the tag is appended onto the tag in the manifest. Sorry if i'm misunderstanding what the intended behavior is here, I'm also using skaffold v1.16.0

[nkubala]

alright, out of curiosity i dug into this one again and was also unable to reproduce. i did run into a few inconsistencies which i think we should track in separate issues, since they're not exactly related to this specific issue.

@yuwenma would you be able to provide more detailed repro instructions? did you use any additional flags on the call to skaffold render? did you manually update your pod.yaml? did you ever update the artifact in your skaffold.yaml?

[nkubala]

@yuwenma with the new render design we're working on, i think this issue is obsolete. i'll close it for now, but feel free and reopen if you think it's still relevant.