What causes an Argo CD application to remain OutOfSync after a sync operation?

Question

An Argo CD application should transition to Synced after a successful sync, but it can stay OutOfSync when the manifest path or revision is incorrect, the destination cluster is unreachable, the argocd-manager service account lacks necessary RBAC permissions, or repository credentials are invalid. Diagnosing the issue requires inspecting sync logs and verifying each of these factors without altering the live configuration prematurely.

How can one verify that the destination server URL is reachable from the Argo CD instance? Which specific RBAC permissions are required for the argocd-manager service account to manage resources in the target namespace? What steps confirm that repository credentials or SSH keys are correctly configured and valid?

Tasadduq Burney · Answer

Why Applications Remain OutOfSync After Syncing

An Argo CD application remains OutOfSync after a successful sync operation when the Live State in the cluster differs from the Desired State defined in Git. Even if the sync process reports success, any immediate modification to the resource by an external actor triggers a new drift detection, reverting the status to OutOfSync.

Likely Explanations for Persistent Drift

While connectivity and RBAC issues typically cause a Sync Failed error, a successful sync that returns to OutOfSync is usually caused by Live State Drift. Common triggers include:

Mutating Admission Webhooks: Cluster-level controllers (e.g., Istio, Linkerd, or custom webhooks) may inject sidecars, labels, or annotations into the pod spec that are not present in your Git manifests.
External Controllers/Operators: HPA (Horizontal Pod Autoscaler) or other operators may modify replica counts or resource limits immediately after Argo CD applies the manifest.
Resource Hooks: Post-sync jobs that modify the target resource can create a state mismatch.
Incorrect ignoreDifferences: If specific fields are managed by the cluster but not explicitly excluded in the Application spec, Argo CD will flag them as differences.

Verification and Resolution Steps

To resolve this, you must identify the specific field causing the drift rather than attempting to re-sync repeatedly.

Analyze the Diff: Use the Argo CD UI to compare the Desired State (Git) and Live State (Cluster). The diff view highlights the exact line causing the mismatch.
Check for Mutating Webhooks: Verify if any webhooks are altering your resources:
```
kubectl get mutatingwebhookconfigurations
```
Configure ignoreDifferences: If the drift is expected (e.g., an injected sidecar), add an ignoreDifferences block to your Application manifest to tell Argo CD to overlook those specific fields.
Verify Connectivity: If you suspect the instance cannot reach the server (causing a failure to update the status), test the connection from the argocd-server or argocd-application-controller pod:
```
kubectl exec -it <argocd-pod-name> -n argocd -- curl -k https://<destination-server-url>
```

Diagnostic Requirement

To provide a more specific recommendation, please provide the diff output from the Argo CD UI showing which specific fields are marked as different.

What causes an Argo CD application to remain OutOfSync after a sync operation?

1 answer

Why Applications Remain OutOfSync After Syncing

Likely Explanations for Persistent Drift

Verification and Resolution Steps

Diagnostic Requirement

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