Admission Controller to modify the git source for ArgoCD Applications

The problem this webhooks solves is that when you are working with a parent ArgoCD Applications that deploy a child ArgoCD Applications, you might need to change something in the child ArgoCD Application using a forked repo, you can't edit the child ArgoCD Application CR on the cluster because the parent App will revert your edit back to what's in git.

You can avoid this by adding an ignoreDifference in the ArgoCD config, but when you are dealing with more than 20 ArgoCD Applications and between parent and children, and a combination of git repositories it becomes hard to first find the correct ArgoCD corresponding to your git repo, this webhook allows you to create a simple mapping configmap to make sure that any ArgoCD Application points to your fork repos, this avoids your fork repos being polluted with your git URLs and keeping the upstream URLs.

• If not using ArgoCD operator edit the argocd-cm configMap

  data:
    resource.customizations: |
      argoproj.io/Application:
        ignoreDifferences: |
          jsonPointers:
          - /spec/source/targetRevision
          - /spec/source/repoURL
      argoproj.io/AppProject:
        ignoreDifferences: |
          jsonPointers:
          - /spec/sourceRepos

• If using the ArgoCD operator then edit the instance of kind ArgoCD

  spec:
    resourceCustomizations: |
      argoproj.io/Application:
        ignoreDifferences: |
          jsonPointers:
          - /spec/source/targetRevision
          - /spec/source/repoURL
      argoproj.io/AppProject:
        ignoreDifferences: |
          jsonPointers:
          - /spec/sourceRepos

• Configure which git repository and/or branch/revision you would like to override. Create a configmap with an array of git repositories to match an upstream and replace with your origin, usually a forked repo and branch.

  cat <<EOF | oc apply -f -
  apiVersion: v1
  kind: ConfigMap
  metadata:
    name: argocd-git-override
    namespace: openshift-gitops
  data:
    map.yaml: |-
      map:
      - upstreamRepoURL: https://github.com/csantanapr/argocd-git-override.git
        originRepoUrL: https://github.com/fork/argocd-git-override.git
        originBranch: fork-branch
  EOF

• Deploy the deployment and service to OpenShift in the openshift-gitops namespace, or another namespace

  oc create -n openshift-gitops  -f https://github.com/csantanapr/argocd-git-override/releases/download/v1.1.0/deployment.yaml

• Deploy the MutatingWebhookConfiguration, edit the yaml to specify a different namespace for the target service if you used a different namespace than openshift-gitops replace it with the namespace used in the previous step

  oc create -f https://github.com/csantanapr/argocd-git-override/releases/download/v1.1.0/webhook.yaml

• Activate webhook, by adding a label to the openshift-gitops namespace you deploy the webhook service

  oc label ns openshift-gitops cntk=experiment

• Change to the openshift-gitops namespace as context

  oc project openshift-gitops
  

• Run dev mode

  skaffold dev

• Test in another terminal to create an ArgoCD Application

  oc create -f test/child/argocd.yaml --dry-run=server -o yaml

• Test in another terminal to create an ArgoCD Project

  oc create -f test/parent/argocd-project.yaml --dry-run=server -o yaml

• To debug delete the quota in the openshift-gitops then run debug

  oc delete quota openshift-gitops-compute-resources -n openshift-gitops

  skaffold debug

  Then you would be able to attach a nodejs debugger