docs/content/v2.0/managed-resources/usages.md

---
title: Usages
weight: 30
state: beta
alphaVersion: "1.14"
betaVersion: "1.19"
description: "Block deletion of in-use resources"
---

A `Usage` indicates a resource is in use. Two main use cases for Usages are
as follows:

1. Protecting a resource from accidental deletion.
2. Deletion ordering by ensuring that a resource isn't deleted before the 
   deletion of its dependent resources.

See the section [Usage for Deletion Protection](#usage-for-deletion-protection) for the
first use case and the section [Usage for Deletion Ordering](#usage-for-deletion-ordering)
for the second one.

## Enable usages
<!-- vale write-good.Passive = NO -->
Usages are a beta feature. Crossplane enables beta features by default.
<!-- vale write-good.Passive = YES -->

Disable `Usage` support by 
[changing the Crossplane pod setting]({{<ref "../guides/pods#change-pod-settings">}})
and setting  
{{<hover label="deployment" line="12">}}--enable-usages=false{{</hover>}}
argument.

```yaml {label="deployment",copy-lines="12"}
$ kubectl edit deployment crossplane --namespace crossplane-system
apiVersion: apps/v1
kind: Deployment
spec:
# Removed for brevity
  template:
    spec:
      containers:
      - args:
        - core
        - start
        - --enable-usages=false
```

{{<hint "tip" >}}

The [Crossplane install guide]({{<ref "../get-started/install#feature-flags">}}) 
describes enabling feature flags like 
{{<hover label="deployment" line="12">}}\-\-enable-usages{{</hover>}}
with Helm.
{{< /hint >}}

<!-- vale Google.Headings = NO -->
## Create a usage
<!-- vale Google.Headings = YES -->

<!-- vale write-good.Passive = NO -->
A {{<hover label="protect" line="2">}}Usage{{</hover>}}
{{<hover label="protect" line="5">}}spec{{</hover>}} has a mandatory
{{<hover label="protect" line="6">}}of{{</hover>}} field for defining the resource
in use or protected. The 
{{<hover label="protect" line="11">}}reason{{</hover>}} field defines the reason
for protection and the {{<hover label="order" line="11">}}by{{</hover>}} field
defines the using resource. Both fields are optional, but at least one of them
must be provided.
<!-- vale write-good.Passive = YES -->

### Usage for deletion protection

The following example prevents the deletion of the 
{{<hover label="protect" line="10">}}my-database{{</hover>}} resource by rejecting
any deletion request with the
{{<hover label="protect" line="11">}}reason{{</hover>}} defined.

```yaml {label="protect"}
apiVersion: protection.crossplane.io/v1beta1
kind: Usage
metadata:
  namespace: default
  name: protect-production-database
spec:
  of:
    apiVersion: rds.aws.m.upbound.io/v1beta1
    kind: Instance
    resourceRef:
      name: my-database
  reason: "Production Database - should never be deleted!"
```

### Usage for deletion ordering

The following example prevents the deletion of
{{<hover label="order" line="10">}}my-cluster{{</hover>}} resource by rejecting
any deletion request before the deletion of 
{{<hover label="order" line="15">}}my-prometheus-chart{{</hover>}} resource.

```yaml {label="order"}
apiVersion: protection.crossplane.io/v1beta1
kind: Usage
metadata:
  namespace: default
  name: release-uses-cluster
spec:
  of:
    apiVersion: eks.m.upbound.io/v1beta1
    kind: Cluster
    resourceRef:
      name: my-cluster
  by:
    apiVersion: helm.m.crossplane.io/v1beta1
    kind: Release
    resourceRef:
      name: my-prometheus-chart
```

### Using selectors with usages

Usages can use {{<hover label="selectors" line="9">}}selectors{{</hover>}}
to define the resource in use or the using one.
This enables using {{<hover label="selectors" line="12">}}labels{{</hover>}} or
{{<hover label="selectors" line="10">}}matching controller references{{</hover>}}
to define resource instead of providing the resource name.

```yaml {label="selectors"}
apiVersion: protection.crossplane.io/v1beta1
kind: Usage
metadata:
  namespace: default
  name: release-uses-cluster
spec:
  of:
    apiVersion: eks.m.upbound.io/v1beta1
    kind: Cluster
    resourceSelector:
      matchControllerRef: false # default, and could be omitted
      matchLabels:
        foo: bar
  by:
    apiVersion: helm.m.crossplane.io/v1beta1
    kind: Release
    resourceSelector:
       matchLabels:
          baz: qux
```

After the `Usage` controller resolves the selectors, it persists the resource
name in the 
{{<hover label="selectors-resolved" line="10">}}resourceRef.name{{</hover>}}
field. The following example shows the `Usage` resource after the resolution of
selectors.

{{<hint "important" >}}
<!-- vale write-good.Passive = NO -->
The selectors are resolved only once. If there are more than one matches, a
random resource is selected from the list of matched resources.
<!-- vale write-good.Passive = YES -->
{{< /hint >}}

```yaml {label="selectors-resolved"}
apiVersion: protection.crossplane.io/v1beta1
kind: Usage
metadata:
  namespace: default
  name: release-uses-cluster
spec:
  of:
    apiVersion: eks.m.upbound.io/v1beta1
    kind: Cluster
    resourceRef:
       name: my-cluster
    resourceSelector:
      matchLabels:
        foo: bar
  by:
    apiVersion: helm.m.crossplane.io/v1beta1
    kind: Release
    resourceRef:
       name: my-cluster
    resourceSelector:
       matchLabels:
          baz: qux
```

### Replay blocked deletion attempt

By default, the deletion of a `Usage` resource doesn't trigger the deletion of
the resource in use even if there were deletion attempts blocked by the `Usage`.
Replaying the blocked deletion is possible by setting the
{{<hover label="replay" line="6">}}replayDeletion{{</hover>}} field to `true`.

```yaml {label="replay"}
apiVersion: protection.crossplane.io/v1beta1
kind: Usage
metadata:
  namespace: default
  name: release-uses-cluster
spec:
  replayDeletion: true
  of:
    apiVersion: eks.m.upbound.io/v1beta1
    kind: Cluster
    resourceRef:
      name: my-cluster
  by:
    apiVersion: helm.m.crossplane.io/v1beta1
    kind: Release
    resourceRef:
      name: my-prometheus-chart
```

{{<hint "tip" >}}

Replay deletion is useful when the used resource is part of a composition.
This configuration radically decreases time for the deletion of the used
resource, hence the composite owning it, by replaying the deletion of the
used resource right after the using resource disappears instead of waiting
for the long exponential backoff durations of the Kubernetes garbage collector.
{{< /hint >}}

## Usage in a Composition

A typical use case for Usages is to define a deletion ordering between the
resources in a Composition. The Usages support
[matching controller reference]({{<ref "./managed-resources#matching-by-controller-reference" >}})
in selectors to ensures that the matching resource is in the same composite
resource in the same way as [cross-resource referencing]({{<ref "./managed-resources#referencing-other-resources" >}}).

{{<hint "tip" >}}

<!-- vale write-good.Passive = NO -->
When there are multiple resources of same type in a Composition, the
{{<hover label="composition" line="18">}}Usage{{</hover>}} resource must
uniquely identify the resource in use or the using one. This could be
accomplished by using extra labels and combining
{{<hover label="composition" line="24">}}matchControllerRef{{</hover>}}
with a `matchLabels` selector. 
<!-- vale write-good.Passive = YES -->
{{< /hint >}}

## Usage across namespaces

A `Usage` with `of` and `by` represents a usage relationship between two
resources in the same namespace as the `Usage` by default.

A `Usage` can represent a usage relationship between a `by` resource in the same
namespace as the `Usage` and an `of` resource in a different namespace.

To use a resource in a different namespace, specify the `namespace` in the `of`
`resourceRef` or `resourceSelector`.

```yaml {label="order"}
apiVersion: protection.crossplane.io/v1beta1
kind: Usage
metadata:
  namespace: default
  name: release-uses-cluster
spec:
  of:
    apiVersion: eks.m.upbound.io/v1beta1
    kind: Cluster
    resourceRef:
      namespace: cluster-infra
      name: my-cluster
  by:
    apiVersion: helm.m.crossplane.io/v1beta1
    kind: Release
    resourceRef:
      name: my-prometheus-chart
```

<!-- vale Google.Headings = NO -->
## ClusterUsages
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Use a `ClusterUsage` to protect cluster scoped resources.

```yaml {label="protect"}
apiVersion: protection.crossplane.io/v1beta1
kind: ClusterUsage
metadata:
  name: protect-important-crd
spec:
  of:
    apiVersion: apiextensions.k8s.io/v1
    kind: CustomResourceDefinition
    resourceRef:
      name: importantresources.example.crossplane.io
  reason: "Very important CRD - should never be deleted!"
```