Automated Sync Policy

Argo CD has the ability to automatically sync an application when it detects differences between the desired manifests in Git, and the live state in the cluster. A benefit of automatic sync is that CI/CD pipelines no longer need direct access to the Argo CD API server to perform the deployment. Instead, the pipeline makes a commit and push to the Git repository with the changes to the manifests in the tracking Git repo.

To configure automated sync run:

  1. argocd app set <APPNAME> --sync-policy automated

Alternatively, if creating the application an application manifest, specify a syncPolicy with an automated policy.

  1. spec:
  2.   syncPolicy:
  3.     automated: {}

Automatic Pruning

By default (and as a safety mechanism), automated sync will not delete resources when Argo CD detects the resource is no longer defined in Git. To prune the resources, a manual sync can always be performed (with pruning checked). Pruning can also be enabled to happen automatically as part of the automated sync by running:

  1. argocd app set <APPNAME> --auto-prune

Or by setting the prune option to true in the automated sync policy:

  1. spec:
  2.   syncPolicy:
  3.     automated:
  4.       prune: true

Automatic Pruning with Allow-Empty (v1.8)

By default (and as a safety mechanism), automated sync with prune have a protection from any automation/human errors when there are no target resources. It prevents application from having empty resources. To allow applications have empty resources, run:

  1. argocd app set <APPNAME> --allow-empty

Or by setting the allow empty option to true in the automated sync policy:

  1. spec:
  2.   syncPolicy:
  3.     automated:
  4.       prune: true
  5.       allowEmpty: true

Automatic Self-Healing

By default, changes that are made to the live cluster will not trigger automated sync. To enable automatic sync when the live cluster’s state deviates from the state defined in Git, run:

  1. argocd app set <APPNAME> --self-heal

Or by setting the self heal option to true in the automated sync policy:

  1. spec:
  2.   syncPolicy:
  3.     automated:
  4.       selfHeal: true

Automated Sync Semantics

  • An automated sync will only be performed if the application is OutOfSync. Applications in a Synced or error state will not attempt automated sync.
  • Automated sync will only attempt one synchronization per unique combination of commit SHA1 and application parameters. If the most recent successful sync in the history was already performed against the same commit-SHA and parameters, a second sync will not be attempted, unless selfHeal flag is set to true.
  • If selfHeal flag is set to true then sync will be attempted again after self heal timeout (5 seconds by default) which is controlled by --self-heal-timeout-seconds flag of argocd-application-controller deployment.

  • Automatic sync will not reattempt a sync if the previous sync attempt against the same commit-SHA and parameters had failed.

  • Rollback cannot be performed against an application with automated sync enabled.

  • The automatic sync interval is determined by the timeout.reconciliation value in the argocd-cm ConfigMap, which defaults to 180s (3 minutes).