Argo CD Sync Phases and Waves

Recently we have Argo CD Sync options with examples, part of that, there is additional options with sync, those are Phases and waves. Why this is matters? This is sometime very useful, if you are expecting some manifest on sequence or some order. Let’s see about Argo CD Phases and waves, in this section.

Sync Phases

Argo CD executes a sync operation in a number of steps. At a high-level, there are three phases pre-sync, sync and post-sync. Within each phase you can have one or more waves, that allows you to ensure certain resources are healthy before subsequent resources are synced.

Synchronization can be configured using resource hooks. Hooks are ways to run scripts before, during, and after a Sync operation. Hooks can also be run if a Sync operation fails at any point. Some use cases for hooks are:

  • Using a PreSync hook to perform a database schema migration before deploying a new version of the app.
  • Using a Sync hook to orchestrate a complex deployment requiring more sophistication than the Kubernetes rolling update strategy.
  • Using a PostSync hook to run integration and health checks after a deployment.
  • Using a SyncFail hook to run clean-up or finalizer logic if a Sync operation fails.

Usage

Hooks are simply Kubernetes manifests tracked in the source repository of your Argo CD Application annotated with argocd.argoproj.io/hook, e.g.:

apiVersion: batch/v1
kind: Job
metadata:
generateName: schema-migrate-
annotations:
argocd.argoproj.io/hook: PreSync

During a Sync operation, Argo CD will apply the resource during the appropriate phase of the deployment. Hooks can be any type of Kubernetes resource kind, but tend to be Pod, Job or Argo Workflows. Multiple hooks can be specified as a comma separated list.

Note:

  • Named hooks (i.e. ones with /metadata/name) will only be created once. If you want a hook to be re-created each time either use BeforeHookCreation policy (see below) or /metadata/generateName.
  • Hooks are not run during selective sync.

Continue reading it on https://foxutech.com/argo-cd-sync-phases-and-waves/

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