crossplane-contrib · vinish86 · Feb 12, 2025
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+---
+apiVersion: apiextensions.crossplane.io/v1
+kind: Composition
+metadata:
+  name: xsingletonresources.example.crossplane.io
+spec:
+  compositeTypeRef:
+    apiVersion: example.crossplane.io/v1
+    kind: XSingletonResource
+  mode: Pipeline
+  pipeline:
+    - step: check-resource-existence-create
+      functionRef:
+        name: function-go-templating
+      input:
+        apiVersion: gotemplating.fn.crossplane.io/v1beta1
+        kind: GoTemplate
+        source: Inline
+        inline:
+          template: |-
+            {{- $resourceSpec := index .observed.composite.resource.spec.resource }}
+            {{- $readyStatus := false -}}
+            {{- $externalName := "" -}}
+            ---
+            apiVersion: meta.gotemplating.fn.crossplane.io/v1alpha1
+            kind: ExtraResources
+            requirements:
+              resources:
+                apiVersion: {{ $resourceSpec.apiVersion }}
+                kind: {{ $resourceSpec.kind }}
+                matchName: {{ $resourceSpec.metadata.name }}
+            {{- with .extraResources }}
+              {{- $someExtraResources := index . "resources" }}
+              {{- range $i, $extraResource := $someExtraResources.items }}
+                {{- $resourceName := $extraResource.resource.metadata.name }}
+                {{- if eq $resourceName  $resourceSpec.metadata.name }}
+                  {{- $extraResourcesStatus := fromJson ($extraResource.resource.status.conditions | toJson) }}
+                  {{- if gt (len $extraResourcesStatus) 1 }}
+                    {{- $syncConditionReadyStatus := index $extraResourcesStatus 1 }}
+                    {{- if eq $syncConditionReadyStatus.status "True" }}  # Assuming "True" indicates readiness
+                      {{- $readyStatus = true -}}  # Set readyStatus to true if condition is met
+                      {{ $externalName = index $extraResource.resource.metadata.annotations "crossplane.io/external-name" }}
+                    {{- else }}
+                      {{- $readyStatus = false -}}
+                    {{- end }}
+                  {{- else }}
+                    {{- $readyStatus = false -}}
+                  {{- end }}
+                {{- else }}
+                  {{- $readyStatus = false -}}
+                {{- end }}
+              {{- end }}
+            {{- end }}
+            {{- if $readyStatus }}
+            ---
+            apiVersion: {{ $resourceSpec.apiVersion }}
+            kind: {{ $resourceSpec.kind }}
+            metadata:
+              name: {{ $resourceSpec.metadata.name }}-readonly-{{ $.observed.composite.resource.metadata.name }}
+              annotations:
+                crossplane.io/external-name: {{ $externalName }}
+                gotemplating.fn.crossplane.io/composition-resource-name: {{ $resourceSpec.metadata.name }}
+            spec:
+            {{- toYaml $resourceSpec.spec | nindent 2 }}
+              managementPolicies: ["Observe"]
+            ---
+            apiVersion: example.crossplane.io/v1
+            kind: XSingletonResource
+            metadata:
+              name: {{ $.observed.composite.resource.metadata.name }}
+            status:
+              externalResourceStatus: "Already exist {{ $resourceSpec.metadata.name }} of kind {{ $resourceSpec.kind }}"
+              externalName: {{ $externalName }}
+            {{- else }}
+            ---
+            apiVersion: {{ $resourceSpec.apiVersion }}
+            kind: {{ $resourceSpec.kind }}
+            metadata:
+              name: {{ $resourceSpec.metadata.name }}
+              annotations:
+                crossplane.io/external-name: {{ $resourceSpec.metadata.name }}
+                gotemplating.fn.crossplane.io/composition-resource-name: {{ $resourceSpec.metadata.name }}
+            spec:
+            {{- toYaml $resourceSpec.spec | nindent 2 }}
+              managementPolicies: ["Observe", "Create"]
+            ---
+            apiVersion: example.crossplane.io/v1
+            kind: XSingletonResource
+            metadata:
+              name: {{ $.observed.composite.resource.metadata.name }}
+            status:
+              externalResourceStatus: "resource name {{ $resourceSpec.metadata.name }} of kind {{ $resourceSpec.kind }} not exist. Creating.."
+              externalName: {{ $externalName }}
+            {{- end }}
+    - step: automatically-detect-ready-composed-resources
+      functionRef:
+        name: function-auto-ready
@@ -0,0 +1,43 @@
+---
+apiVersion: apiextensions.crossplane.io/v1
+kind: CompositeResourceDefinition
+metadata:
+  name: xsingletonresources.example.crossplane.io
+spec:
+  group: example.crossplane.io
+  defaultCompositeDeletePolicy: Foreground
+  names:
+    kind: XSingletonResource
+    plural: xsingletonresources
+    singular: xsingletonresource
+  claimNames:
+    kind: SingletonResource
+    plural: singletonresources
+    singular: singletonresource
+  versions:
+    - name: v1
+      served: true
+      referenceable: true
+      schema:
+        openAPIV3Schema:
+          type: object
+          properties:
+            spec:
+              type: object
+              required:
+                - resource
+              properties:
+                resource:
+                  description: Freeform field for resource
+                  type: object
+                  x-kubernetes-preserve-unknown-fields: true
+            status:
+              description: XRStatus defines the observed state of XR.
+              type: object
+              properties:
+                externalResourceStatus:
+                  type: string
+                  description: status of the resource
+                externalName:
+                  type: string
+                  description: external name of the MR
@@ -0,0 +1,14 @@
+---
+apiVersion: pkg.crossplane.io/v1beta1
+kind: Function
+metadata:
+  name: function-go-templating
+spec:
+  package: xpkg.upbound.io/crossplane-contrib/function-go-templating:v0.9.1
+---
+apiVersion: pkg.crossplane.io/v1beta1
+kind: Function
+metadata:
+  name: function-auto-ready
+spec:
+  package: xpkg.upbound.io/crossplane-contrib/function-auto-ready:v0.4.1
@@ -0,0 +1,136 @@
+# How It Works  
+
+## Overview  
+This mechanism leverages Crossplane Composition, Go templating, and management policies to dynamically determine whether a cloud resource should be observed (imported) or created (managed). It uses Crossplane's ExtraResources feature, a powerful Go templating capability, to check if a requested resource already exists in the cloud and handle it accordingly.
+
+1. **ExtraResources** fetch MR information
+2. **Imported (Observed Only)** if it already exists in the cloud.  
+3. **Created and Managed** if it does not exist.  
+
+The mechanism leverages **Crossplane Composition** and **management policies** to determine whether the resource should be observed or created.  
+
+---
+
+## Step-by-Step Execution  
+
+### 1️⃣ Extracting the Requested Resource Specification  
+The template begins by extracting the required resource details from the **observed composite resource**:  
+
+```yaml
+{{- $resourceSpec := index .observed.composite.resource.spec.resource }}
+```  
+
+- `$resourceSpec` holds information such as `apiVersion`, `kind`, `metadata.name`, and `spec`.  
+- A default **ready status (`$readyStatus`)** is set to `false`.  
+- An empty **external name (`$externalName`)** is initialized.  
+
+---
+
+### 2️⃣ Checking for Existing Resources  
+The logic then checks whether this resource already exists in **extraResources**:  
+
+```yaml
+{{- with .extraResources }}
+  {{- $someExtraResources := index . "resources" }}
+  {{- range $i, $extraResource := $someExtraResources.items }}
+    {{- $resourceName := $extraResource.resource.metadata.name }}
+```  
+
+For each `extraResource`:  
+- If the `metadata.name` matches `$resourceSpec.metadata.name`, it means an instance of this resource may already exist.  
+- The **status conditions** are parsed:  
+
+  ```yaml
+  {{- $extraResourcesStatus := fromJson ($extraResource.resource.status.conditions | toJson) }}
+  ```  
+
+- If there is more than one condition:  
+  - The **second condition** (`syncConditionReadyStatus`) is checked to determine if it is `"True"` (i.e., the resource is ready).  
+  - If **ready**, `$readyStatus` is set to `true`, and the `external-name` annotation is extracted:  
+
+    ```yaml
+    {{ $externalName = index $extraResource.resource.metadata.annotations "crossplane.io/external-name" }}
+    ```  
+
+- If the conditions are missing or not `"True"`, `$readyStatus` remains `false`.  
+
+---
+
+### 3️⃣ Handling the Resource Based on Readiness
+
+#### ✅ **Case 1: Resource Already Exists**  
+If `$readyStatus` is `true`:  
+
+- A **read-only Crossplane resource** is created, importing the existing cloud resource using an `external-name`:  
+
+  ```yaml
+  apiVersion: {{ $resourceSpec.apiVersion }}
+  kind: {{ $resourceSpec.kind }}
+  metadata:
+    name: {{ $resourceSpec.metadata.name }}-readonly-{{ $.observed.composite.resource.metadata.name }}
+    annotations:
+      crossplane.io/external-name: {{ $externalName }}
+  spec:
+    managementPolicies: ["Observe"]
+  ```  
+
+- A **singleton status resource** (`XSingletonResource`) is updated to indicate that the resource already exists:  
+
+  ```yaml
+  apiVersion: example.crossplane.io/v1
+  kind: XSingletonResource
+  metadata:
+    name: {{ $.observed.composite.resource.metadata.name }}
+  status:
+    externalResourceStatus: "Already exist {{ $resourceSpec.metadata.name }} of kind {{ $resourceSpec.kind }}"
+    externalName: {{ $externalName }}
+  ```  
+
+---
+
+#### ❌ **Case 2: Resource Does Not Exist**  
+If `$readyStatus` is `false`:  
+
+- A **new resource is created and managed** by Crossplane with `managementPolicies: ["Observe", "Create"]`:  
+
+  ```yaml
+  apiVersion: {{ $resourceSpec.apiVersion }}
+  kind: {{ $resourceSpec.kind }}
+  metadata:
+    name: {{ $resourceSpec.metadata.name }}
+    annotations:
+      crossplane.io/external-name: {{ $resourceSpec.metadata.name }}
+  spec:
+    managementPolicies: ["Observe", "Create"]
+  ```  
+
+- A **singleton status resource** (`XSingletonResource`) is updated to indicate that the resource is being created:  
+
+  ```yaml
+  apiVersion: example.crossplane.io/v1
+  kind: XSingletonResource
+  metadata:
+    name: {{ $.observed.composite.resource.metadata.name }}
+  status:
+    externalResourceStatus: "resource name {{ $resourceSpec.metadata.name }} of kind {{ $resourceSpec.kind }} not exist. Creating.."
+    externalName: {{ $externalName }}
+  ```  
+
+---
+
+## Summary  
+
+| Condition | Action Taken |
+|-----------|-------------|
+| **Resource exists** in cloud (determined via `extraResources`) | Import as **read-only** with `"Observe"` policy. |
+| **Resource does not exist** | Create a new resource and manage it with `"Observe", "Create"` policies. |
+
+### Key Benefits  
+✅ Prevents duplicate resource creation in the cloud.  
+✅ Ensures the correct resource is always referenced.  
+✅ Keeps resources in **read-only mode** to prevent accidental modifications.  
+✅ Allows claims to share the same cloud resource while maintaining unique metadata inside Kubernetes.  
+
+---
+
+This explanation should provide a clear understanding of how the template works. Let me know if you need any refinements! 🚀
@@ -0,0 +1,16 @@
+---
+apiVersion: example.crossplane.io/v1
+kind: XSingletonResource
+metadata:
+  name: example-xr1
+spec:
+  resource:
+    apiVersion: azure.upbound.io/v1beta1
+    kind: ResourceGroup
+    metadata:
+      name: testrg
+    spec:
+      forProvider:
+        location: West Europe
+      providerConfigRef:
+        name: default
@@ -0,0 +1,16 @@
+---
+apiVersion: example.crossplane.io/v1
+kind: XSingletonResource
+metadata:
+  name: example-xr2
+spec:
+  resource:
+    apiVersion: azure.upbound.io/v1beta1
+    kind: ResourceGroup
+    metadata:
+      name: testrg
+    spec:
+      forProvider:
+        location: West Europe
+      providerConfigRef:
+        name: default
@@ -0,0 +1,16 @@
+---
+apiVersion: example.crossplane.io/v1
+kind: XSingletonResource
+metadata:
+  name: example-xr3
+spec:
+  resource:
+    apiVersion: azure.upbound.io/v1beta1
+    kind: ResourceGroup
+    metadata:
+      name: testrg
+    spec:
+      forProvider:
+        location: West Europe
+      providerConfigRef:
+        name: default