# Reconcile Optimization

By default, an Argo CD Application is refreshed every time a resource that belongs to it changes.

Kubernetes controllers often update the resources they watch periodically, causing continuous reconcile operation on the Application
and a high CPU usage on the `argocd-application-controller`. Argo CD allows you to optionally ignore resource updates on specific fields
for [tracked resources](../user-guide/resource_tracking.md).
For untracked resources, you can [use the argocd.argoproj.io/ignore-resource-updates annotations](#ignoring-updates-for-untracked-resources)

When a resource update is ignored, if the resource's [health status](./health.md) does not change, the Application that this resource belongs to will not be reconciled.

## System-Level Configuration

By default, `resource.ignoreResourceUpdatesEnabled` is set to `true`, enabling Argo CD to ignore resource updates. This default setting ensures that Argo CD maintains sustainable performance by reducing unnecessary reconcile operations. If you need to alter this behavior, you can explicitly set `resource.ignoreResourceUpdatesEnabled` to `false` in the `argocd-cm` ConfigMap:

```yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: argocd-cm
  namespace: argocd
data:
  resource.ignoreResourceUpdatesEnabled: 'false'
```

Argo CD allows ignoring resource updates at a specific JSON path, using [RFC6902 JSON patches](https://tools.ietf.org/html/rfc6902) and [JQ path expressions](<https://stedolan.github.io/jq/manual/#path(path_expression)>). It can be configured for a specified group and kind
in `resource.customizations` key of the `argocd-cm` ConfigMap.

Following is an example of a customization which ignores the `refreshTime` status field of an [`ExternalSecret`](https://external-secrets.io/main/api/externalsecret/) resource:

```yaml
data:
  resource.customizations.ignoreResourceUpdates.external-secrets.io_ExternalSecret:
    |
    jsonPointers:
    - /status/refreshTime
    # JQ equivalent of the above:
    # jqPathExpressions:
    # - .status.refreshTime
```

It is possible to configure `ignoreResourceUpdates` to be applied to all tracked resources in every Application managed by an Argo CD instance. In order to do so, resource customizations can be configured like in the example below:

```yaml
data:
  resource.customizations.ignoreResourceUpdates.all: |
    jsonPointers:
    - /status
```

### Using ignoreDifferences to ignore reconcile

By default, the existing system-level `ignoreDifferences` customizations will be added to ignore resource updates as well. This helps reduce config management by preventing you to copy all existing ignore differences configurations.

To disable this behavior, the `ignoreDifferencesOnResourceUpdates` setting can be disabled:

```yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: argocd-cm
data:
  resource.compareoptions: |
    ignoreDifferencesOnResourceUpdates: false
```

## Default Configuration

By default, the metadata fields `generation`, `resourceVersion` and `managedFields` are always ignored for all resources.

## Finding Resources to Ignore

The application controller logs when a resource change triggers a refresh. You can use these logs to find
high-churn resource kinds and then inspect those resources to find which fields to ignore.

To find these logs, search for `"Requesting app refresh caused by object update"`. The logs include structured
fields for `api-version` and `kind`. Counting the number of refreshes triggered, by api-version/kind should
reveal the high-churn resource kinds.

> [!NOTE]
> These logs are at the `info` level for GitOps managed resources and `debug` level for orphan and dependedant resources. Configure the application-controller's log level to `debug` to have the most details, and use `comparison-level` fields to know the importance of that resource update.

Once you have identified some resources which change often, you can try to determine which fields are changing. Here is
one approach:

```shell
kubectl get <resource> -o yaml > /tmp/before.yaml
# Wait a minute or two.
kubectl get <resource> -o yaml > /tmp/after.yaml
diff /tmp/before.yaml /tmp/after.yaml
```

The diff can give you a sense for which fields are changing and should perhaps be ignored.

## Checking Whether Resource Updates are Ignored

Whenever Argo CD skips a refresh due to an ignored resource update, the controller logs the following line:
"Ignoring change of object because none of the watched resource fields have changed".

Search the application-controller logs for this line to confirm that your resource ignore rules are being applied.

> [!NOTE]
> These logs are at the `debug` level. Configure the application-controller's log level to `debug`.

## Examples

### argoproj.io/Application

```yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: argocd-cm
data:
  resource.customizations.ignoreResourceUpdates.argoproj.io_Application: |
    jsonPointers:
    # Ignore when ownerReferences change, for example when a parent ApplicationSet changes often.
    - /metadata/ownerReferences
    # Ignore reconciledAt, since by itself it doesn't indicate any important change.
    - /status/reconciledAt
    jqPathExpressions:
    # Ignore lastTransitionTime for conditions; helpful when SharedResourceWarnings are being regularly updated but not
    # actually changing in content.
    - .status?.conditions[]?.lastTransitionTime
```

## Ignoring updates for untracked resources

ArgoCD will only apply `ignoreResourceUpdates` configuration to tracked resources of an application. This means dependent resources, such as a `ReplicaSet` and `Pod` created by a `Deployment`, will not ignore any updates and trigger a reconcile of the application for any changes.

If you want to apply the `ignoreResourceUpdates` configuration to an untracked resource, you can add the
`argocd.argoproj.io/ignore-resource-updates=true` annotation in the dependent resources manifest.

## Example

### CronJob

```yaml
apiVersion: batch/v1
kind: CronJob
metadata:
  name: hello
  namespace: test-cronjob
spec:
  schedule: '* * * * *'
  jobTemplate:
    metadata:
      annotations:
        argocd.argoproj.io/ignore-resource-updates: 'true'
    spec:
      template:
        metadata:
          annotations:
            argocd.argoproj.io/ignore-resource-updates: 'true'
        spec:
          containers:
            - name: hello
              image: busybox:1.28
              imagePullPolicy: IfNotPresent
              command:
                - /bin/sh
                - -c
                - date; echo Hello from the Kubernetes cluster
          restartPolicy: OnFailure
```

The resource updates will be ignored based on your the `ignoreResourceUpdates` configuration in the `argocd-cm` configMap:

`argocd-cm`:

```yaml
resource.customizations.ignoreResourceUpdates.batch_Job: |
  jsonPointers:
    - /status
resource.customizations.ignoreResourceUpdates.Pod: |
  jsonPointers:
    - /status
```
