Controlling if/when the ApplicationSet controller modifies `Application` resources¶

The ApplicationSet controller supports a number of settings that limit the ability of the controller to make changes to generated Applications, for example, preventing the controller from deleting child Applications.

These settings allow you to exert control over when, and how, changes are made to your Applications, and to their corresponding cluster resources (Deployments, Services, etc).

Here are some of the controller settings that may be modified to alter the ApplicationSet controller's resource-handling behaviour.

Dry run: prevent ApplicationSet from creating, modifying, or deleting all Applications¶

To prevent the ApplicationSet controller from creating, modifying, or deleting any Application resources, you may enable dry-run mode. This essentially switches the controller into a "read only" mode, where the controller Reconcile loop will run, but no resources will be modified.

To enable dry-run, add --dryrun true to the ApplicationSet Deployment's container launch parameters.

See 'How to modify ApplicationSet container parameters' below for detailed steps on how to add this parameter to the controller.

Managed Applications modification Policies¶

The ApplicationSet controller supports a parameter --policy, which is specified on launch (within the controller Deployment container), and which restricts what types of modifications will be made to managed Argo CD Application resources.

The --policy parameter takes four values: sync, create-only, create-delete, and create-update. (sync is the default, which is used if the --policy parameter is not specified; the other policies are described below).

It is also possible to set this policy per ApplicationSet.

apiVersion: argoproj.io/v1alpha1
kind: ApplicationSet
spec:
  # (...)
  syncPolicy:
    applicationsSync: create-only # create-update, create-delete sync

Policy create-only: Prevents ApplicationSet controller from modifying or deleting Applications.
Policy create-update: Prevents ApplicationSet controller from deleting Applications. Update is allowed.
Policy create-delete: Prevents ApplicationSet controller from modifying Applications. Delete is allowed.
Policy sync: Update and Delete are allowed.

If the controller parameter --policy is set, it takes precedence on the field applicationsSync. It is possible to allow per ApplicationSet sync policy by setting variable ARGOCD_APPLICATIONSET_CONTROLLER_ENABLE_POLICY_OVERRIDE to argocd-cmd-params-cm applicationsetcontroller.enable.policy.override or directly with controller parameter --enable-policy-override (default to false).

This does not prevent deletion of Applications if the ApplicationSet is deleted

Controller parameter¶

To allow the ApplicationSet controller to create Application resources, but prevent any further modification, such as deletion, or modification of Application fields, add this parameter in the ApplicationSet controller:

--policy create-only

At ApplicationSet level

apiVersion: argoproj.io/v1alpha1
kind: ApplicationSet
spec:
  # (...)
  syncPolicy:
    applicationsSync: create-only

Policy - `create-update`: Prevent ApplicationSet controller from deleting Applications¶

To allow the ApplicationSet controller to create or modify Application resources, but prevent Applications from being deleted, add the following parameter to the ApplicationSet controller Deployment:

--policy create-update

This may be useful to users looking for additional protection against deletion of the Applications generated by the controller.

At ApplicationSet level

apiVersion: argoproj.io/v1alpha1
kind: ApplicationSet
spec:
  # (...)
  syncPolicy:
    applicationsSync: create-update

Ignore certain changes to Applications¶

The ApplicationSet spec includes an ignoreApplicationDifferences field, which allows you to specify which fields of the ApplicationSet should be ignored when comparing Applications.

The field supports multiple ignore rules. Each ignore rule may specify a list of either jsonPointers or jqPathExpressions to ignore.

You may optionally also specify a name to apply the ignore rule to a specific Application, or omit the name to apply the ignore rule to all Applications.

apiVersion: argoproj.io/v1alpha1
kind: ApplicationSet
spec:
  ignoreApplicationDifferences:
    - jsonPointers:
        - /spec/source/targetRevision
    - name: some-app
      jqExpressions:
        - .spec.source.helm.values

Prevent an `Application`'s child resources from being deleted, when the parent Application is deleted¶

By default, when an Application resource is deleted by the ApplicationSet controller, all of the child resources of the Application will be deleted as well (such as, all of the Application's Deployments, Services, etc).

To prevent an Application's child resources from being deleted when the parent Application is deleted, add the preserveResourcesOnDeletion: true field to the syncPolicy of the ApplicationSet:

apiVersion: argoproj.io/v1alpha1
kind: ApplicationSet
spec:
  # (...)
  syncPolicy:
    preserveResourcesOnDeletion: true

More information on the specific behaviour of preserveResourcesOnDeletion, and deletion in ApplicationSet controller and Argo CD in general, can be found on the Application Deletion page.

Prevent an Application's child resources from being modified¶

Changes made to the ApplicationSet will propagate to the Applications managed by the ApplicationSet, and then Argo CD will propagate the Application changes to the underlying cluster resources (as per Argo CD Integration).

The propagation of Application changes to the cluster is managed by the automated sync settings, which are referenced in the ApplicationSet template field:

spec.template.syncPolicy.automated: If enabled, changes to Applications will automatically propagate to the cluster resources of the cluster.
- Unset this within the ApplicationSet template to 'pause' updates to cluster resources managed by the Application resource.
spec.template.syncPolicy.automated.prune: By default, Automated sync will not delete resources when Argo CD detects the resource is no longer defined in Git.
- For extra safety, set this to false to prevent unexpected changes to the backing Git repository from affecting cluster resources.

How to modify ApplicationSet container launch parameters¶

There are a couple of ways to modify the ApplicationSet container parameters, so as to enable the above settings.

A) Use `kubectl edit` to modify the deployment on the cluster¶

Edit the applicationset-controller Deployment resource on the cluster:

kubectl edit deployment/argocd-applicationset-controller -n argocd

Locate the .spec.template.spec.containers[0].command field, and add the required parameter(s):

spec:
    # (...)
  template:
    # (...)
    spec:
      containers:
      - command:
        - entrypoint.sh
        - argocd-applicationset-controller
        # Insert new parameters here, for example:
        # --policy create-only
    # (...)

Save and exit the editor. Wait for a new Pod to start containing the updated parameters.

Or, B) Edit the `install.yaml` manifest for the ApplicationSet installation¶

Rather than directly editing the cluster resource, you may instead choose to modify the installation YAML that is used to install the ApplicationSet controller:

Applicable for applicationset versions less than 0.4.0.

# Clone the repository

git clone https://github.com/argoproj/applicationset

# Checkout the version that corresponds to the one you have installed.
git checkout "(version of applicationset)"
# example: git checkout "0.1.0"

cd applicationset/manifests

# open 'install.yaml' in a text editor, make the same modifications to Deployment 
# as described in the previous section.

# Apply the change to the cluster
kubectl apply -n argocd -f install.yaml

Preserving changes made to an Applications annotations and labels¶

It is common practice in Kubernetes to store state in annotations, operators will often make use of this. To allow for this, it is possible to configure a list of annotations that the ApplicationSet should preserve when reconciling.

For example, imagine that we have an Application created from an ApplicationSet, but a custom annotation and label has since been added (to the Application) that does not exist in the ApplicationSet resource:

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  # This annotation and label exists only on this Application, and not in 
  # the parent ApplicationSet template:
  annotations: 
    my-custom-annotation: some-value
  labels:
    my-custom-label: some-value
spec:
  # (...)

To preserve this annotation and label we can use the preservedFields property of the ApplicationSet like so:

apiVersion: argoproj.io/v1alpha1
kind: ApplicationSet
spec:
  # (...)
  preservedFields:
    annotations: ["my-custom-annotation"]
    labels: ["my-custom-label"]

The ApplicationSet controller will leave this annotation and label as-is when reconciling, even though it is not defined in the metadata of the ApplicationSet itself.

By default, the Argo CD notifications and the Argo CD refresh type annotations are also preserved.

Note

One can also set global preserved fields for the controller by passing a comma separated list of annotations and labels to ARGOCD_APPLICATIONSET_CONTROLLER_GLOBAL_PRESERVED_ANNOTATIONS and ARGOCD_APPLICATIONSET_CONTROLLER_GLOBAL_PRESERVED_LABELS respectively.

Controlling if/when the ApplicationSet controller modifies Application resources¶