Argocd + env var + applicationset + kustomize

[soudaburger]

We are running into an issue where we would like to simply add an environment variable FOO to an applicationset so that the image.tag (as an example) can be overwritten in the kustomize template rendering.

1. We are using a combination of kustomize with helm, but from an applicationset perspective we are NOT using the helm: configuration, just relying on the built in kustomize + --enable-helm flag.
2. We have a separate repository that contains our image versions (for a multitude of reasons) and we'd like to be able to interpolate those into kustomize for rendering so that argo will not only deploy the new version as set but also not see any deltas or diffs with the applicationset.
3. We are using argocd 2.4.2 on GKE.

We continue to see references to the CMP where we are "supposed" to just be able to use:

        plugin:
          env:
            - name: IMAGETAG
              value: "{{version}}"

However, when using that we run into :

rpc error: code = Unknown desc = plugin sidecar failed. Couldn't find cmp-server plugin supporting repository .apps/core-api/deploy/overlays/staging

So, how, exactly are we supposed to add an environment variable to kustomize templating from an applicationset? I know how to retrieve it on the templating side, but setting it on the applicationset seems to either be impossible or completely undocumented? Any pointers here or help would be fantastic! Thanks!

Documentation Sources:

1. https://github.com/argoproj/argo-cd/blob/master/docs/user-guide/config-management-plugins.md#environment
2. https://argo-cd.readthedocs.io/en/stable/user-guide/config-management-plugins/#environment

[soudaburger]

Actually I solved my own problem, but this was a HUGE combination of documented pieces from around the web... ok so here are the pieces...

In my applicationSet:

        plugin:
          env:
            - name: IMAGETAG
              value: "{{version}}"
          name: kustomized-helm

In argocd helm configuration for plugins:

    # server.config.configManagementPlugins
    configManagementPlugins: |
      - name: kustomized-helm
        generate:
          command: ["/bin/sh", "-c"]
          args: ["IMAGETAG=${ARGOCD_ENV_IMAGETAG} kustomize build --enable-helm"]

Local kustomization.yaml:

configMapGenerator:
  - name: image-tag-var
    env: image.tag.properties

replacements:
  - path: image-tag-replacement.yaml

Local image.tag.properties:

IMAGETAG

Notice the deployment name and the containers.[name=] sections... those are things to make it all work together.

Local image-tag-replacement.yaml

source:
  kind: ConfigMap
  name: image-tag-var
  fieldPath: data.IMAGETAG
  version: v1
targets:
- select:
    name: my-deployment
    kind: Deployment
  fieldPaths:
    - spec.template.spec.containers.[name=my-container].image
  options:
    delimiter: ':'
    index: 1
    create: true

[raebbar]

You can set the image tag within an ApplicationSet without any extras.

apiVersion: argoproj.io/v1alpha1
kind: ApplicationSet
metadata:
  name: foo
spec:
  generators:
    [...]
  template:
    metadata:
      name: 'foo-review-{{number}}'
      [...]
    spec:
      source:
        repoURL: XXXXXX.git
        targetRevision: HEAD
        path: 'XXXX'
        kustomize:
          images:
            - example.com/foo:{{version}}
      destination:
        [...]

[pantmal]

@raebbar This covers only the image tag however. If you want to change any other values, then you will have to go with soudaburger's approach.

[raebbar]

@pantmal You're right, this only works for image tags. For other values, as you said, you have to use the soudaburger's approach.

For those interested: I described another solution without an extra Argocd plugin and ConfigMap in discussion 9042.

[pantmal]

I'm trying to use this for my setup as well but I have encountered a problem: When I want to open a new PR, a new app is created but it also updates the existing ones too. Do we have a solution and/or an explanation of why this occurs? I tried the same setup with Helm and everything works as expected.

[amine7777]

I recently had to create a custom Config Management Plugin (CMP) for Carvel ytt, and I ran into a similar challenge.
My setup had a single common template but multiple sets of data values in different folders, and I needed a way to dynamically tell the plugin which values.yaml file to use when generating manifests.

Initially, I wasn’t sure how to pass those dynamic arguments from an ApplicationSet into the plugin.
Thanks to this discussion, I learned that defining environment variables under the plugin.env section in the ApplicationSet and referencing them as ARGOCD_ENV_* in the plugin command works perfectly.

However, I ran into a subtle but important issue with how the command was defined in the plugin spec:

Common Mistake	Correct Form
command: ["/usr/local/bin/ytt"] + args: ["ytt -f . ${ARGOCD_ENV_YTT_EXTRA_ARGS}"]	❌ Runs ytt twice and fails with “does not accept extra arguments”
command: ["/bin/sh", "-c"] + args: ["ytt -f . ${ARGOCD_ENV_YTT_EXTRA_ARGS}"]	✅ Shell expands the environment variable and runs correctly

The issue happened because Argo CD executes the command directly (without a shell),
so the string ytt -f . ${ARGOCD_ENV_YTT_EXTRA_ARGS} was passed literally as an argument to ytt.
Switching to ["/bin/sh", "-c"] lets the shell expand ${ARGOCD_ENV_YTT_EXTRA_ARGS} before calling ytt.

This change finally allowed me to pass per-application arguments like:

configManagementPlugins: |
  - name: carvel-ytt-cmp
    generate:
      command: ["/bin/sh", "-c"]
      args: ["ytt -f . ${ARGOCD_ENV_YTT_EXTRA_ARGS}"]

plugin:
  name: carvel-ytt-cmp
  env:
    - name: YTT_EXTRA_ARGS
      value: "-f path/to/values.yml"