`argocd-wait` step

[jessesuen]

Proposed Feature

argocd-update only waits until a sync operation completes. However, in applications that have no PostSync hooks or sync waves, this will return immediately, as the sync is essentially a kubectl apply of all manifests.

We need something equivalent to the CLI's:

argocd app wait my-app

NOTE: Kargo already has a wait for health functionality. This occurs as part of an "implicit verification" process to ensure an app is healthy before running analysis. However, this process may be happening too late for some use cases.

Motivation

Users often prefer that the app sync and wait happen as part of a promotion, instead of verification. Some use cases:

1. In an app that contains multiple argocd-updates for different microservices (e.g. backend + frontend) as in the "grouped services" pattern, the backend may need to reach health before the frontend is updated

2. Post update steps, like notifications, could be sent only after ensuring apps are healthy after the update.

[jessesuen]

A gross workaround is to add a PostSync hook resource to the Application. The resource could even be an empty configmap. This changes the Argo CD sync operation to wait until the PostSync phase completes, ensuring that after the argocd-update step is complete, the Application is in a Healthy state.

[bmbferreira]

If you're facing issues with sync waves that get into SyncError state and nothing fails on kargo, then I think the issue might be related with what is described on #5166 and with the fix I'm trying to do here

[singhvibhanshu]

Hi @jessesuen!
I've dug into the code and would like to implement this.

i'll add a new built-in step argocd-wait in pkg/promotion/runner/builtin/.

this step will allow users to pause a promotion until specific apps reach a healthy/synced state.

steps:
- uses: argocd-wait
  config:
    apps:
    - name: guestbook
      namespace: argocd   
    healthStatus: Healthy 
    syncStatus: Synced    
    timeout: 5m           

the step will reuse the existing Argo CD client to poll this application status. it'll essentially be a blocking loop that checks: app.Status.Health.Status == desiredHealth && app.Status.Sync.Status == desiredSync

does this schema align with your vision?
if so, i can open a PR for this shortly

[krancour]

@singhvibhanshu anywhere that Kargo touches Argo CD are some of the most complex and high stakes parts of the code. I have to insist that this is handled by a maintainer. In fact, this is still marked as a proposal because we've not yet discussed this adequately amongst ourselves.

[singhvibhanshu]

Understood, @krancour!

I completely respect the complexity and high stakes involved with the Argo CD integration. I'll step back from the implementation for now and look for other ways to contribute.

In the meantime, I’m happy to help with smaller tasks, UI fixes, or testing to help make Kargo even better. If there are other areas where you think a contributor's help would be valuable, please let me know!