kro

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### Basic `includeWhen` Example

Source: https://kro.run/docs/concepts/rgd/resource-definitions/conditional-creation

A simple example demonstrating a single `includeWhen` condition for a resource.

```yaml
- id: monitor
  includeWhen:
    - ${schema.spec.monitoring.enabled}
```

--------------------------------

### Apply Raw Manifest for kro Installation

Source: https://kro.run/docs/getting-started/Installation

Installs kro using a raw manifest URL, specifying the version and variant. Ensure the namespace is created beforehand.

```bash
kubectl create namespace kro-system
kubectl apply -f https://github.com/kubernetes-sigs/kro/releases/download/v$KRO_VERSION/$KRO_VARIANT.yaml
```

--------------------------------

### Basic Collection Example with `forEach`

Source: https://kro.run/docs/concepts/rgd/resource-definitions/collections

This example demonstrates how to use `forEach` to create multiple Pods from a single resource definition. When an instance is created with a list of workers, kro generates a Pod for each worker.

```yaml
apiVersion: kro.run/v1alpha1
kind: ResourceGraphDefinition
metadata:
  name: worker-pool
spec:
  schema:
    apiVersion: v1alpha1
    kind: WorkerPool
    spec:
      workers: "[]string"
      image: string

  resources:
    - id: workerPods
      forEach:
        - worker: ${schema.spec.workers}
      template:
        apiVersion: v1
        kind: Pod
        metadata:
          name: ${schema.metadata.name + '-' + worker}
        spec:
          containers:
            - name: app
              image: ${schema.spec.image}
```

--------------------------------

### Example Topological Order Output

Source: https://kro.run/docs/concepts/rgd/dependencies-ordering

Shows an example of the JSONPath output for the topological order of resources.

```json
status:
  topologicalOrder:
    - configmap
    - deployment
    - service
```

--------------------------------

### kro Drift Detection Example

Source: https://kro.run/docs/concepts/rgd/resource-definitions/collections

This example demonstrates how kro detects and restores drifted resource fields. It shows the sequence of events from creation to manual modification and kro's automatic correction.

```bash
# 1. kro creates ConfigMap with data.prefix: "original"  
# 2. Someone manually changes data.prefix to "MODIFIED"  
# 3. kro detects the drift and restores data.prefix to "original"  

```

--------------------------------

### Complete RGD Example with Schema and Resources

Source: https://kro.run/docs/concepts/rgd/schema

A comprehensive example demonstrating a Resource Graph Definition (RGD) including schema definition with basic and structured configurations, status fields, conditional fields, additional printer columns, and resource definitions.

```yaml
apiVersion: kro.run/v1alpha1
kind: ResourceGraphDefinition
metadata:
  name: web-application
spec:
  schema:
    apiVersion: v1alpha1
    kind: WebApplication

    spec:
      # Basic configuration
      name: string | required=true
      replicas: integer | default=3 minimum=1
      image: string | required=true

      # Structured configuration
      ingress:
        enabled: boolean | default=false
        host: string
        path: string | default="/"

      # Collections
      env: "map[string]string"
      ports: "[]integer | default=[80]"

    status:
      # Resource state
      availableReplicas: ${deployment.status.availableReplicas}
      serviceIP: ${service.spec.clusterIP}

      # Conditional fields (only present if ingress enabled)
      ingressHost: ${ingress.spec.rules[0].host}

    additionalPrinterColumns:
      - name: Replicas
        type: integer
        jsonPath: .spec.replicas
      - name: Available
        type: integer
        jsonPath: .status.availableReplicas
      - name: Image
        type: string
        jsonPath: .spec.image

  resources:
    - id: deployment
      template:
        apiVersion: apps/v1
        kind: Deployment
        # ... deployment configuration using ${schema.spec.*} ...

    - id: service
      template:
        apiVersion: v1
        kind: Service
        # ... service configuration ...

    - id: ingress
      includeWhen:
        - ${schema.spec.ingress.enabled}
      template:
        apiVersion: networking.k8s.io/v1
        kind: Ingress
        # ... ingress configuration ...
```

--------------------------------

### Install Specific kro Version with Helm

Source: https://kro.run/docs/getting-started/Installation

Install a specific version of kro for reproducible deployments by setting the KRO_VERSION environment variable.

```bash
# Set the version you want to install
export KRO_VERSION=0.9.1

# Install kro
helm install kro oci://registry.k8s.io/kro/charts/kro \
  --namespace kro-system \
  --create-namespace \
  --version=${KRO_VERSION}
```

--------------------------------

### Install Latest Release Version of kro with Helm

Source: https://kro.run/docs/getting-started/Installation

Automatically install the latest release version of kro by fetching the tag name from the GitHub API and then using it with Helm.

```bash
# Fetch latest release version
export KRO_VERSION=$(curl -sL \
    https://api.github.com/repos/kubernetes-sigs/kro/releases/latest | \
    jq -r '.tag_name | ltrimstr("v")')

# Verify version
echo $KRO_VERSION

# Install kro
helm install kro oci://registry.k8s.io/kro/charts/kro \
  --namespace kro-system \
  --create-namespace \
  --version=${KRO_VERSION}
```

--------------------------------

### Example Schema with Various Field Types and Markers

Source: https://kro.run/api/specifications/simple-schema

A comprehensive example showcasing different data types and validation markers, including string, integer, float, and array types.

```yaml
name: string | required=true default="app" description="Application name"
id: string | required=true immutable=true description="Unique identifier"
replicas: integer | default=3 minimum=1 maximum=10
price: float | minimum=0.01 maximum=999.99
mode: string | enum="debug,info,warn,error" default="info"
email: string | pattern="^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\\.[a-zA-Z]{2,}$" description="Valid email address"
username: string | minLength=3 maxLength=20 pattern="^[a-zA-Z0-9_]+""
tags: '[]string | uniqueItems=true minItems=1 maxItems=10 description="1-10 unique tags"'
```

--------------------------------

### Example RGD Status Output

Source: https://kro.run/docs/getting-started/deploy-a-resource-graph-definition

This is an example of the output you should expect after successfully deploying and inspecting an RGD. It shows the RGD's name, API version, kind, state, readiness, topological order, and age.

```text
NAME             APIVERSION   KIND          STATE    READY   TOPOLOGICALORDER                     AGE  
my-application   v1alpha1     Application   Active   True    ["deployment","service","ingress"]   49  

```

--------------------------------

### Validate ResourceGraphDefinition Installation

Source: https://kro.run/examples/gcp/gke-cluster

Verify that the RGD is installed correctly by getting its status.

```bash
kubectl get rgd gkecluster.kro.run  

```

--------------------------------

### Get Deployed Resources

Source: https://kro.run/docs/getting-started/deploy-a-resource-graph-definition

Inspect the Deployment, Service, and Ingress resources created by the Application instance.

```bash
kubectl get deployments,services,ingresses

```

--------------------------------

### Verify kro Pod is Running

Source: https://kro.run/docs/getting-started/Installation

Check the status of the kro pods to ensure they are running after installation.

```bash
kubectl get pods -n kro-system
```

--------------------------------

### Get Instance Ready Condition

Source: https://kro.run/docs/concepts/instances

Use this command to check the 'Ready' condition of an instance. This is the first step in debugging instance state.

```bash
kubectl get <your-kind> <instance-name> -o jsonpath='{.status.conditions[?(@.type=="Ready")]}'  
```

--------------------------------

### Get Application Instances

Source: https://kro.run/docs/getting-started/deploy-a-resource-graph-definition

Check the status of deployed Application instances.

```bash
kubectl get applications

```

--------------------------------

### Install Latest kro Version with Helm

Source: https://kro.run/docs/getting-started/Installation

Use this command to install the latest available version of kro on your Kubernetes cluster using Helm.

```bash
helm install kro oci://registry.k8s.io/kro/charts/kro \
  --namespace kro-system \
  --create-namespace
```

--------------------------------

### Resource Definition with References

Source: https://kro.run/docs/concepts/rgd/resource-definitions/resource-basics

This example shows how to define multiple resources and reference properties from the schema and other resources. Kro automatically determines dependencies based on these references.

```yaml
spec:
  resources:
    - id: database
      template:
        apiVersion: database.example.com/v1
        kind: PostgreSQL
        metadata:
          # Reference instance spec
          name: ${schema.spec.name}-db
          # Reference instance metadata
          namespace: ${schema.metadata.namespace}
          labels: ${schema.metadata.labels}
        spec:
          version: "15"
          storage: ${schema.spec.storageSize}
          replicas: 2

    - id: deployment
      template:
        apiVersion: apps/v1
        kind: Deployment
        metadata:
          name: ${schema.spec.name}
          namespace: ${schema.metadata.namespace}
          # Reference another resource's metadata
          annotations: ${database.metadata.annotations}
        spec:
          replicas: ${schema.spec.replicas}
          selector:
            matchLabels:
              app: ${schema.spec.name}
          template:
            spec:
              containers:
                - name: app
                  image: ${schema.spec.image}
                  env:
                    # Reference another resource's status
                    - name: DATABASE_HOST
                      value: ${database.status.endpoint}
                    # Reference another resource's spec
                    - name: DATABASE_VERSION
                      value: ${database.spec.version}
```

--------------------------------

### Install ResourceGraphDefinition

Source: https://kro.run/examples/gcp/gke-cluster

Apply the RGD definition to your cluster using kubectl.

```bash
kubectl apply -f rgd.yaml  

```

--------------------------------

### Type Checking Example

Source: https://kro.run/docs/concepts/rgd/cel-expressions

kro performs compile-time type checking. This example shows an RGD that would be rejected because the `appName` (string) is assigned to `replicas` (integer).

```yaml
spec:
  replicas: ${schema.spec.appName}  # Error: appName is string, replicas expects integer
```

--------------------------------

### Collection Readiness with `each`

Source: https://kro.run/docs/concepts/rgd/resource-definitions/readiness

This example shows how to define readiness for items within a collection using the `each` keyword. It ensures each worker pod is in a 'Running' phase before the collection is considered ready.

```yaml
# ✓ Valid for collections - uses each for per-item readiness
- id: workerPods
  forEach:
    - worker: ${schema.spec.workers}
  readyWhen:
    - ${each.status.phase == 'Running'}
  template:
    kind: Pod
    metadata:
      name: ${schema.metadata.name + '-' + worker}
```

--------------------------------

### Define Database and App Readiness

Source: https://kro.run/docs/concepts/rgd/resource-definitions/readiness

This example demonstrates how to define readiness for a database and then use its status to configure an application deployment. The application will only be created after the database is fully ready, including having an endpoint.

```yaml
resources:
  - id: database
    template:
      apiVersion: database.example.com/v1
      kind: PostgreSQL
      metadata:
        name: ${schema.spec.name}-db
      spec:
        version: "15"
    readyWhen:
      - ${database.status.conditions.exists(c, c.type == "Ready" && c.status == "True")}
      - ${database.status.?endpoint != ""}

  - id: app
    template:
      apiVersion: apps/v1
      kind: Deployment
      metadata:
        name: ${schema.spec.name}
      spec:
        template:
          spec:
            containers:
              - name: app
                image: ${schema.spec.image}
                env:
                  - name: DATABASE_HOST
                    value: ${database.status.endpoint}
```

--------------------------------

### Get Kro Instance Status

Source: https://kro.run/docs/concepts/instances

Use `kubectl get webapplication` to retrieve a high-level overview of your instance's status, including its readiness and age.

```bash
$ kubectl get webapplication my-app  
NAME     STATUS    READY   AGE  
my-app   ACTIVE    true    30s  


```

--------------------------------

### Validate RGD Installation

Source: https://kro.run/examples/gcp/cloud-sql

Verify that the CloudSQL RGD has been installed and is in an Active state. This command checks the status and age of the installed RGD.

```bash
> kubectl get rgd cloudsql.kro.run
NAME               APIVERSION   KIND       STATE    AGE  
cloudsql.kro.run   v1alpha1     CloudSQL   Active   44m  
```

--------------------------------

### Install ResourceGraphDefinition

Source: https://kro.run/examples/gcp/cloud-sql

Apply the RGD definition to the cluster using kubectl. Ensure the rgd.yaml file is in the current directory.

```bash
kubectl apply -f rgd.yaml
```

--------------------------------

### Simple Schema Example: Image String

Source: https://kro.run/

Defines an 'image' field as a string with a default value of 'nginx' within a SimpleSchema.

```yaml
image: string | default=nginx
```

--------------------------------

### Resource Readiness Conditions

Source: https://kro.run/docs/concepts/rgd/resource-definitions/readiness

Examples of valid `readyWhen` expressions for a resource. These expressions must reference the resource itself and evaluate to a boolean.

```yaml
# ✓ Valid - references the resource itself and returns boolean
- id: deployment
  readyWhen:
    - ${deployment.status.availableReplicas > 0}
    - ${deployment.status.conditions.exists(c, c.type == "Available" && c.status == "True")}
```

--------------------------------

### WebApplication RGD Example

Source: https://kro.run/docs/building-abstractions/rgd-chaining

Defines a WebApplication RGD that creates a Deployment, Service, and Ingress. It uses templating to configure the application image and database connection URL.

```yaml
apiVersion: kro.run/v1alpha1
kind: ResourceGraphDefinition
metadata:
  name: web-application
spec:
  schema:
    apiVersion: v1alpha1
    kind: WebApplication
    spec:
      name: string
      image: string
      databaseUrl: string | default=""
    status:
      ready: ${deployment.status.availableReplicas == 2}
      endpoint: "https://${schema.spec.name}.example.com"

  resources:
    - id: deployment
      template:
        apiVersion: apps/v1
        kind: Deployment
        metadata:
          name: ${schema.spec.name}
        spec:
          replicas: 2
          selector:
            matchLabels:
              app: ${schema.spec.name}
          template:
            metadata:
              labels:
                app: ${schema.spec.name}
            spec:
              containers:
                - name: app
                  image: ${schema.spec.image}
                  env:
                    - name: DATABASE_URL
                      value: ${schema.spec.databaseUrl}
                  ports:
                    - containerPort: 8080
      readyWhen:
        - ${deployment.status.availableReplicas == 2}

    - id: service
      template:
        apiVersion: v1
        kind: Service
        metadata:
          name: ${schema.spec.name}
        spec:
          selector:
            app: ${schema.spec.name}
          ports:
            - port: 80
              targetPort: 8080

    - id: ingress
      template:
        apiVersion: networking.k8s.io/v1
        kind: Ingress
        metadata:
          name: ${schema.spec.name}
        spec:
          rules:
            - host: ${schema.spec.name}.example.com
              http:
                paths:
                  - path: /
                    pathType: Prefix
                    backend:
                      service:
```

--------------------------------

### Define a WebApp API with kro

Source: https://kro.run/docs/overview

This is an example of a user-defined API instance for a WebApp. It specifies the image and bucket name for the application.

```yaml
apiVersion: kro.run/v1alpha1
kind: WebApp
metadata:
  name: my-app
spec:
  image: nginx
  bucketName: my-app-assets

```

--------------------------------

### Reference a Shared ConfigMap in a Deployment

Source: https://kro.run/docs/concepts/rgd/resource-definitions/external-references

This example shows how an application Deployment references a shared ConfigMap for configuration. The Deployment will only be created after the ConfigMap exists and its data is accessible.

```yaml
resources:
  - id: sharedConfig
    externalRef:
      apiVersion: v1
      kind: ConfigMap
      metadata:
        name: platform-config
        namespace: platform-system

  - id: app
    template:
      apiVersion: apps/v1
      kind: Deployment
      metadata:
        name: ${schema.spec.name}
      spec:
        template:
          spec:
            containers:
              - name: app
                image: ${schema.spec.image}
                env:
                  - name: PLATFORM_URL
                    value: ${sharedConfig.data.?platformUrl}
                  - name: REGION
                    value: ${sharedConfig.data.?region}
```

--------------------------------

### Linear Chain Dependency Example

Source: https://kro.run/docs/concepts/rgd/dependencies-ordering

Illustrates a linear dependency where each resource depends on the previous one, suitable for sequential processing.

```yaml
resources:
  - id: configmap
    template:
      apiVersion: v1
      kind: ConfigMap
      data:
        key: ${schema.spec.value}

  - id: deployment
    template:
      apiVersion: apps/v1
      kind: Deployment
      spec:
        template:
          spec:
            containers:
              - envFrom:
                  - configMapRef:
                      name: ${configmap.metadata.name}

  - id: service
    template:
      apiVersion: v1
      kind: Service
      spec:
        selector: ${deployment.spec.selector.matchLabels}
```

--------------------------------

### Database RGD Example

Source: https://kro.run/docs/building-abstractions/rgd-chaining

Defines a Database RGD that creates a StatefulSet, Secret, and Service. It exposes status fields like `ready` and `connectionString` for use by parent RGDs.

```yaml
apiVersion: kro.run/v1alpha1
kind: ResourceGraphDefinition
metadata:
  name: database
spec:
  schema:
    apiVersion: v1alpha1
    kind: Database
    spec:
      size: string | default="small"
    status:
      ready: ${statefulset.status.readyReplicas == 1}
      connectionString: "postgresql://postgres@${service.metadata.name}:5432/postgres"

  resources:
    - id: secret
      template:
        apiVersion: v1
        kind: Secret
        metadata:
          name: ${schema.metadata.name}-credentials
        stringData:
          password: changeme

    - id: statefulset
      template:
        apiVersion: apps/v1
        kind: StatefulSet
        metadata:
          name: ${schema.metadata.name}
        spec:
          serviceName: ${schema.metadata.name}
          replicas: 1
          selector:
            matchLabels:
              app: ${schema.metadata.name}
          template:
            metadata:
              labels:
                app: ${schema.metadata.name}
            spec:
              containers:
                - name: postgres
                  image: postgres:15
                  env:
                    - name: POSTGRES_PASSWORD
                      valueFrom:
                        secretKeyRef:
                          name: ${secret.metadata.name}
                          key: password
      readyWhen:
        - ${statefulset.status.readyReplicas == 1}

    - id: service
      template:
        apiVersion: v1
        kind: Service
        metadata:
          name: ${schema.metadata.name}
        spec:
          selector:
            app: ${schema.metadata.name}
          ports:
            - port: 5432
```

--------------------------------

### Exact Type Match Examples

Source: https://kro.run/docs/concepts/rgd/cel-expressions

Demonstrates correct and incorrect type assignments for integer fields. Ensure the expression result matches the target field's type.

```cel
# ✓ Correct: integer to integer
replicas: ${schema.spec.replicaCount}
```

```cel
# ✗ Wrong: string to integer
replicas: ${schema.spec.appName}
```

--------------------------------

### Get Specific GCSBucketWithFinalizerTrigger Details

Source: https://kro.run/examples/gcp/eventarc

Fetch the detailed YAML configuration and status for a specific GCSBucketWithFinalizerTrigger resource named 'gcsevent-test' in the 'config-connector' namespace.

```bash
kubectl get gcsbucketwithfinalizertrigger gcsevent-test -n config-connector -o yaml
```

--------------------------------

### Parallel Branches Dependency Example

Source: https://kro.run/docs/concepts/rgd/dependencies-ordering

Demonstrates parallel branches where resources have no interdependencies and can be created concurrently, ideal for independent components like microservices.

```yaml
resources:
  - id: api
    template:
      apiVersion: apps/v1
      kind: Deployment
      metadata:
        name: ${schema.spec.name}-api

  - id: worker
    template:
      apiVersion: apps/v1
      kind: Deployment
      metadata:
        name: ${schema.spec.name}-worker

  - id: cron
    template:
      apiVersion: batch/v1
      kind: CronJob
      metadata:
        name: ${schema.spec.name}-cron
```

--------------------------------

### Conditionally Create Ingress

Source: https://kro.run/docs/concepts/rgd/resource-definitions/conditional-creation

This example shows how to conditionally create an Ingress resource based on a boolean flag in the instance spec. The Ingress is only created if `schema.spec.ingress.enabled` is true.

```yaml
resources:
  - id: ingress
    includeWhen:
      - ${schema.spec.ingress.enabled}
    template:
      apiVersion: networking.k8s.io/v1
      kind: Ingress
      metadata:
        name: ${schema.spec.name}
      # ... rest of ingress configuration
```

--------------------------------

### FullStackApp RGD Example

Source: https://kro.run/docs/building-abstractions/rgd-chaining

Defines a parent RGD that composes Database and WebApplication RGDs. It uses templating to dynamically set resource names and pass status information between child RGDs.

```yaml
apiVersion: kro.run/v1alpha1
kind: ResourceGraphDefinition
metadata:
  name: full-stack-app
spec:
  schema:
    apiVersion: v1alpha1
    kind: FullStackApp
    spec:
      name: string
      dbSize: string | default="small"
    status:
      databaseReady: ${database.status.ready}
      appEndpoint: ${webapp.status.endpoint}

  resources:
    # Use an instance of the Database RGD
    - id: database
      template:
        apiVersion: kro.run/v1alpha1
        kind: Database
        metadata:
          name: ${schema.spec.name}-db
        spec:
          size: ${schema.spec.dbSize}
      readyWhen:
        - ${database.status.ready == true}

    # Use an instance of the WebApplication RGD
    - id: webapp
      template:
        apiVersion: kro.run/v1alpha1
        kind: WebApplication
        metadata:
          name: ${schema.spec.name}-web
        spec:
          name: ${schema.spec.name}
          image: myapp:latest
          databaseUrl: ${database.status.connectionString}
```

--------------------------------

### Struct Subset Semantics - Valid Example

Source: https://kro.run/docs/concepts/rgd/cel-expressions

Demonstrates a valid use of struct subset semantics where the expression result provides a subset of the expected fields for a container.

```cel
# ✓ Valid: subset of expected fields
containers:
  - ${{"name": "app", "image": schema.spec.image}}
```

--------------------------------

### Working with Collections using CEL

Source: https://kro.run/docs/concepts/rgd/resource-definitions/external-references

Access and manipulate external resource collections using CEL. Examples include getting the count, extracting names, filtering, and checking for existence.

```yaml
# Number of matching resources
configCount: ${string(size(teamConfigs))}

# Extract names
names: ${teamConfigs.map(c, c.metadata.name).join(",")}

# Filter by a data field
critical: ${teamConfigs.filter(c, c.data.?priority == "critical")}

# Check if any match a condition
hasCritical: ${teamConfigs.exists(c, c.data.?priority == "critical")}
```

--------------------------------

### Enforce Naming Conventions with RGD

Source: https://kro.run/docs/building-abstractions/single-resource-rgd

This RGD example demonstrates wrapping a ServiceAccount, enforcing naming conventions derived from the instance namespace and a 'team' label, and exposing the generated name in the status.

```yaml
apiVersion: kro.run/v1alpha1
kind: ResourceGraphDefinition
metadata:
  name: teamserviceaccount.platform
spec:
  schema:
    apiVersion: v1alpha1
    kind: TeamServiceAccount
    spec:
      name: string
    status:
      generatedName: ${serviceAccount.metadata.name}

  resources:
    - id: serviceAccount
      template:
        apiVersion: v1
        kind: ServiceAccount
        metadata:
          namespace: ${schema.metadata.namespace}
          name: ${schema.metadata.namespace + "-" + schema.metadata.?labels["team"].orValue("platform") + "-" + schema.spec.name + "-sa"}
```

--------------------------------

### Get WebApp instance status with kubectl

Source: https://kro.run/docs/overview

After kro has reconciled the resources, this command retrieves the status of the WebApp instance, showing generated details like bucket ARN.

```bash
$ kubectl get webapp my-app -o yaml
status:
  bucketArn: arn:aws:s3:::my-app-assets

```

--------------------------------

### Get All Graph Revisions

Source: https://kro.run/docs/advanced/graph-revisions

Use `kubectl get gr` or `kubectl get graphrevisions` to list all graph revisions. The `READY` column indicates compilation success (`True`), failure (`False`), or pending status (`Unknown`).

```bash
kubectl get gr
# or
kubectl get graphrevisions
```

--------------------------------

### Schema Validation Example

Source: https://kro.run/docs/concepts/rgd/static-type-checking

kro validates the SimpleSchema definition provided in spec.schema. This example shows a basic schema structure.

```yaml
spec:
  schema:
    spec:
      # kro validates this schema definition
      replicas: integer | default=3
      ports: array
      labels: object
```

--------------------------------

### Apply Tenant Instance

Source: https://kro.run/examples/kubernetes/saas-multi-tenant

Apply the tenant instance configuration to create a specific tenant's resources.

```bash
kubectl apply -f tenant-instance.yaml
```

--------------------------------

### Diamond Dependency Pattern Example

Source: https://kro.run/docs/concepts/rgd/dependencies-ordering

Shows a diamond pattern where multiple independent resources converge into a single dependent resource, useful for applications requiring multiple backing services.

```yaml
resources:
  - id: database
    template:
      apiVersion: databases.example.com/v1
      kind: PostgreSQL
      spec:
        name: ${schema.spec.name}-db

  - id: cache
    template:
      apiVersion: caches.example.com/v1
      kind: Redis
      spec:
        name: ${schema.spec.name}-cache

  - id: app
    template:
      apiVersion: apps/v1
      kind: Deployment
      spec:
        template:
          spec:
            containers:
              - env:
                  - name: DATABASE_URL
                    value: ${database.status.endpoint}
                  - name: CACHE_URL
                    value: ${cache.status.endpoint}
```

--------------------------------

### Create Application Instance YAML

Source: https://kro.run/docs/getting-started/deploy-a-resource-graph-definition

Define an Application instance with specified name, replicas, and ingress settings.

```yaml
apiVersion: kro.run/v1alpha1
kind: Application
metadata:
  name: my-app-instance
spec:
  name: my-app
  replicas: 1
  ingress:
    enabled: true

```

--------------------------------

### Manually Add Owner References to Resources

Source: https://kro.run/docs/concepts/instances

Example of how to manually set owner references in resource templates when needed for specific integrations. Use with caution as it may lead to unexpected behavior.

```yaml
resources:
  - id: configmap
    template:
      apiVersion: v1
      kind: ConfigMap
      metadata:
        name: ${schema.spec.name}-config
        ownerReferences:
          - apiVersion: ${schema.apiVersion}
            kind: ${schema.kind}
            name: ${schema.metadata.name}
            uid: ${schema.metadata.uid}
            controller: true
            blockOwnerDeletion: true
```

--------------------------------

### Circular Dependency Example

Source: https://kro.run/docs/concepts/rgd/dependencies-ordering

This example demonstrates a circular dependency where serviceA depends on serviceB and serviceB depends on serviceA. This will cause a reconciliation failure.

```yaml
resources:
  - id: serviceA
    template:
      spec:
        targetPort: ${serviceB.spec.port}  # A → B

  - id: serviceB
    template:
      spec:
        targetPort: ${serviceA.spec.port}  # B → A (circular!)
```

--------------------------------

### Circular Dependency Detection Example

Source: https://kro.run/docs/concepts/rgd/static-type-checking

kro detects circular dependencies by identifying cycles in the resource DAG. This example shows a simple A -> B -> A cycle.

```yaml
# ✗ This fails validation
resources:
  - id: serviceA
    template:
      spec:
        port: ${serviceB.spec.targetPort}  # A → B

  - id: serviceB
    template:
      spec:
        targetPort: ${serviceA.spec.port}  # B → A (cycle!)

```

--------------------------------

### Apply Application Instance with kubectl

Source: https://kro.run/docs/getting-started/deploy-a-resource-graph-definition

Deploy the Application instance to your Kubernetes cluster using kubectl.

```bash
kubectl apply -f instance.yaml

```

--------------------------------

### Nested Field Type Checking Example

Source: https://kro.run/docs/concepts/rgd/static-type-checking

kro recursively checks type compatibility at any depth within nested structures. This example shows a type error in a deeply nested field.

```yaml
spec:
  template:
    spec:
      containers:
        - env:
            - name: PORT
              # Expression returns: int
              # Field path: spec.template.spec.containers[].env[].value
              # Field expects: string
              # kro resolves the full nested path and checks compatibility
              value: ${schema.spec.port}  # ✗ Type error: int → string
```

--------------------------------

### Create a WebApplication Instance

Source: https://kro.run/docs/concepts/instances

Define an instance of the WebApplication custom resource. This specifies the application's name, image, and ingress configuration.

```yaml
apiVersion: kro.run/v1alpha1
kind: WebApplication
metadata:
  name: my-app
spec:
  name: web-app
  image: nginx:latest
  ingress:
    enabled: true

```

--------------------------------

### Describe Instance for Conditions and Events

Source: https://kro.run/docs/concepts/instances

Use `kubectl describe` to view all conditions and recent events for an instance. This provides a comprehensive overview of the instance's state and any issues.

```bash
kubectl describe <your-kind> <instance-name>  
```

--------------------------------

### CEL Expression Type Checking Example

Source: https://kro.run/docs/concepts/rgd/static-type-checking

This example demonstrates the type checking process for a CEL expression, showing inferred and expected types, and the compatibility result. Ensure your CEL expressions are type-safe and compatible with the target schema fields.

```cel
# Expression: ${schema.spec.replicas}
# Inferred output type: integer (from schema.spec definition)
# Expected type: integer (from Deployment.spec.replicas schema)
# Result: ✓ Compatible
```

--------------------------------

### Build pprof Debug Image

Source: https://kro.run/docs/advanced/controller-tuning

Use these Make targets when building or publishing the pprof-enabled image. Ensure GOFLAGS are set if using 'image.ko=true' or 'ko apply'.

```bash
make build-debug-image RELEASE_VERSION=v0.9.1
```

```bash
make publish-debug-image RELEASE_VERSION=v0.9.1
```

--------------------------------

### Invalid includeWhen Expression

Source: https://kro.run/docs/concepts/rgd/resource-definitions/conditional-creation

An example of an invalid `includeWhen` expression that does not return a boolean value.

```yaml
# ✗ Invalid - must return boolean
includeWhen:
  - ${schema.spec.appName}  # returns string, not boolean
```

--------------------------------

### Get KRO ResourceGraphDefinitions

Source: https://kro.run/

Use kubectl to retrieve all ResourceGraphDefinition resources managed by KRO.

```bash
kubectl get resourcegraphdefinitions
```

--------------------------------

### Get GCSBucketWithFinalizerTrigger Status

Source: https://kro.run/examples/gcp/eventarc

Use kubectl to retrieve the status of all GCSBucketWithFinalizerTrigger resources in the 'config-connector' namespace.

```bash
kubectl get gcsbucketwithfinalizertrigger -n config-connector
```

--------------------------------

### Collection Readiness with 'each' Keyword

Source: https://kro.run/docs/concepts/rgd/resource-definitions/collections

Defines a collection 'workerPods' where readiness is determined by each item meeting a specific status condition. The collection is ready only when all items are 'Running'.

```yaml
- id: workerPods
  forEach:
    - worker: ${schema.spec.workers}
  readyWhen:
    - ${each.status.phase == 'Running'}  # Per-item check using `each`
  template:
    kind: Pod
    metadata:
      name: ${schema.metadata.name + '-' + worker}
    spec:
      containers:
        - name: app
          image: ${schema.spec.image}
```

--------------------------------

### Get Topological Order

Source: https://kro.run/docs/concepts/rgd/dependencies-ordering

Retrieves the computed topological order of resources from the RGD status using kubectl.

```bash
kubectl get rgd my-app -o jsonpath='{.status.topologicalOrder}'
```

--------------------------------

### List kro-created resources with kubectl

Source: https://kro.run/docs/overview

This command lists the Kubernetes resources (ConfigMap, Bucket, Deployment, Service) that kro automatically created based on the WebApp definition.

```bash
$ kubectl get configmap,bucket,deploy,svc
NAME                    AGE
configmap/my-app-config 45s

NAME                                       AGE
bucket.s3.services.k8s.aws/my-app-assets   45s

NAME                     READY   AGE
deployment.apps/my-app   1/1     45s

NAME             TYPE        PORT(S)
service/my-app   ClusterIP   80/TCP

```

--------------------------------

### Upgrade kro to Latest Version with Helm

Source: https://kro.run/docs/getting-started/Installation

Upgrade an existing kro Helm installation to the latest available version.

```bash
helm upgrade kro oci://registry.k8s.io/kro/charts/kro \
  --namespace kro-system
```

--------------------------------

### Standalone Boolean Field Expression

Source: https://kro.run/docs/concepts/rgd/cel-expressions

Example of a standalone CEL expression for a boolean field. The result must be a boolean.

```yaml
enabled: ${schema.spec.featureEnabled}
```

--------------------------------

### Define a Web Application Resource Graph

Source: https://kro.run/api/specifications/simple-schema

This example demonstrates defining a namespaced WebApplication resource with various field types, including strings, integers, booleans, objects, arrays, and maps, along with custom types and status field references.

```yaml
apiVersion: kro.run/v1alpha1
kind: ResourceGraphDefinition
metadata:
  name: web-application
spec:
  schema:
    apiVersion: v1alpha1
    kind: WebApplication
    scope: Namespaced  # or "Cluster" for cluster-scoped instances
    spec:
      # Basic types
      name: string | required=true immutable=true description="My Name"
      replicas: integer | default=1 minimum=1 maximum=100
      image: string | required=true

      # Unstructured objects
      values: object | required=true

      # Structured type
      ingress:
        enabled: boolean | default=false
        host: string | default="example.com"
        path: string | default="/"

      # Array type
      ports: "[]integer"

      # Map type
      env: "map[string]myType"

    # Custom Types
    types:
      myType:
        value1: string | required=true
        value2: integer | default=42

    status:
      # Status fields with auto-inferred types
      availableReplicas: ${deployment.status.availableReplicas}
      serviceEndpoint: ${service.status.loadBalancer.ingress[0].hostname}
```

--------------------------------

### Valid includeWhen Expressions

Source: https://kro.run/docs/concepts/rgd/resource-definitions/conditional-creation

Examples of valid `includeWhen` expressions that reference `schema.spec` fields and return boolean values.

```yaml
# ✓ Valid - references schema.spec and returns boolean
includeWhen:
  - ${schema.spec.ingress.enabled}
  - ${schema.spec.environment == "production"}
  - ${schema.spec.replicas > 3}
```

```yaml
# ✓ Valid - references an upstream resource
includeWhen:
  - ${deployment.status.availableReplicas > 0}
```

--------------------------------

### Watch Deployment Scaling

Source: https://kro.run/docs/getting-started/deploy-a-resource-graph-definition

Monitor the deployment as it scales up to the new replica count.

```bash
kubectl get deployment my-app

```

--------------------------------

### Referencing External Resources and Dependencies

Source: https://kro.run/docs/concepts/rgd/resource-definitions/external-references

Define an external resource and show how it creates a dependency chain with other resources. kro waits for external resources before creating dependent ones.

```yaml
resources:
  - id: platformConfig
    externalRef:
      apiVersion: v1
      kind: ConfigMap
      metadata:
        name: platform-config

  - id: database
    template:
      spec:
        region: ${platformConfig.data.?region}

  - id: app
    template:
      spec:
        env:
          - name: DB_ENDPOINT
            value: ${database.status.endpoint}
```

--------------------------------

### Generate Integer Range with lists.range()

Source: https://kro.run/docs/concepts/rgd/cel-libraries

Create a list of integers starting from 0 up to (but not including) the specified number `n`.

```cel
indices: ${lists.range(schema.spec.count)}
```

--------------------------------

### Check Tenant Instance Status

Source: https://kro.run/examples/kubernetes/saas-multi-tenant

Verify the status and synchronization of the applied tenant instance.

```bash
kubectl get tenant
```

--------------------------------

### Defining Resource Dependencies with Collections

Source: https://kro.run/docs/concepts/rgd/resource-definitions/collections

Illustrates how collections establish dependencies. 'backupJobs' depends on 'databases', and 'summary' depends on 'backupJobs', ensuring sequential reconciliation.

```yaml
resources:
  # Collection A: creates multiple databases
  - id: databases
    forEach:
      - dbSpec: ${schema.spec.databases}
    template:
      kind: Database
      metadata:
        name: ${schema.metadata.name + '-' + dbSpec.name}
      # ...

  # Collection B: depends on Collection A
  # kro waits for ALL databases to be ready before creating backup jobs
  - id: backupJobs
    forEach:
      - db: ${databases}
    template:
      kind: CronJob
      metadata:
        name: ${schema.metadata.name + '-backup-' + db.metadata.name}
      # ...

  # Resource C: depends on Collection B
  # kro waits for ALL backup jobs to be ready before creating the summary
  - id: summary
    template:
      kind: ConfigMap
      metadata:
        name: ${schema.metadata.name + '-summary'}
      data:
        backupCount: ${string(size(backupJobs))}
```

--------------------------------

### Enable Feature Gates via Command-Line Flag

Source: https://kro.run/docs/advanced/feature-gates

Pass feature gates directly to the controller binary using the '--feature-gates' flag, separating multiple gates with commas.

```bash
--feature-gates=CELOmitFunction=true,InstanceConditionEvents=true
```

--------------------------------

### Get GraphRevision Topological Order

Source: https://kro.run/docs/advanced/graph-revisions

After a successful compilation, retrieve the resource creation order from the `status.topologicalOrder` field of a graph revision.

```bash
kubectl get gr my-webapp-r00003 -o jsonpath='{.status.topologicalOrder}'
```

```json
["config","bucket","deployment","service"]
```

--------------------------------

### Apply Tenant Environment RGD

Source: https://kro.run/examples/kubernetes/saas-multi-tenant

Apply the tenant environment ResourceGraphDefinition to set up isolated namespaces with resource quotas and NetworkPolicy.

```bash
kubectl apply -f tenant-environment-rgd.yaml
```

--------------------------------

### Tolerant Version Parsing with CEL

Source: https://kro.run/docs/concepts/rgd/cel-libraries

Demonstrates tolerant parsing of version strings using CEL's `isSemver` and `semver` functions. Allows for formats like 'v1.0' and '01.02.03'.

```cel
valid: ${isSemver(schema.spec.version, true)}
parsed: ${semver(schema.spec.version, true).minor()}
```

--------------------------------

### Example of Dimension Explosion

Source: https://kro.run/docs/concepts/rgd/resource-definitions/collections

Illustrates how multiplying dimensions can lead to a large number of resources. Keep iterator lists bounded to avoid this.

```text
3 regions × 5 tiers × 10 shards = 150 resources  
```

--------------------------------

### Resource Template Validation

Source: https://kro.run/docs/concepts/rgd/static-type-checking

kro validates resource templates against Kubernetes OpenAPI schemas. This example shows a basic Deployment template.

```yaml
resources:
  - id: deployment
    template:
      apiVersion: apps/v1  # kro fetches Deployment schema
      kind: Deployment
      # ... validates template against Deployment schema
```

--------------------------------

### String Template with Simple Concatenation

Source: https://kro.run/docs/concepts/rgd/cel-expressions

A string template example showing simple concatenation of a literal string and a CEL expression result.

```yaml
name: "app-${schema.spec.name}"
```

--------------------------------

### Fetch Latest Release Version and Set Variant

Source: https://kro.run/docs/getting-started/Installation

This snippet fetches the latest release version of kro from GitHub and sets the desired installation variant. It's a precursor to applying the raw manifest.

```bash
export KRO_VERSION=$(curl -sL \
      https://api.github.com/repos/kubernetes-sigs/kro/releases/latest | \
      jq -r '.tag_name | ltrimstr("v")'
   )
export KRO_VARIANT=kro-core-install-manifests

echo $KRO_VERSION
```

--------------------------------

### Resource Naming Validation

Source: https://kro.run/docs/concepts/rgd/static-type-checking

Resource IDs must be valid CEL identifiers. Avoid hyphens, special characters, and starting with numbers.

```yaml
# ✓ Valid IDs
resources:
  - id: deployment
  - id: configMap
  - id: servicePrimary

# ✗ Invalid IDs
resources:
  - id: my-deployment  # Hyphens not allowed (CEL subtraction operator)
  - id: 1st-service    # Can't start with number
```

--------------------------------

### Printf-style Formatting with String.format()

Source: https://kro.run/docs/concepts/rgd/cel-libraries

Use the `format()` function for printf-style string formatting, supporting placeholders like %s, %d, %f, %e, %b, %x, %X, and %o. Requires a list of arguments.

```cel
roleArn: ${"arn:aws:iam::%s:role/%s".format([schema.spec.accountId, schema.spec.roleName])}
```

--------------------------------

### Upgrade kro to Specific Version with Helm

Source: https://kro.run/docs/getting-started/Installation

Upgrade an existing kro Helm installation to a specific version by setting the KRO_VERSION environment variable.

```bash
export KRO_VERSION=0.9.1

helm upgrade kro oci://registry.k8s.io/kro/charts/kro \
  --namespace kro-system \
  --version=${KRO_VERSION}
```

--------------------------------

### Watch Service Recreation

Source: https://kro.run/docs/getting-started/deploy-a-resource-graph-definition

Observe kro automatically recreating the service after it has been deleted.

```bash
kubectl get service my-app-svc -w

```

--------------------------------

### String Template with Literal Text and Expressions

Source: https://kro.run/docs/concepts/rgd/cel-expressions

Example of a string template that combines literal text with multiple CEL expressions to form a message.

```yaml
message: "Application ${schema.spec.name} is running version ${schema.spec.version}"
```

--------------------------------

### Instance Spec for Conditional Ingress

Source: https://kro.run/docs/concepts/rgd/resource-definitions/conditional-creation

This is an example of an instance spec where the `ingress.enabled` field is set to true, which would result in the Ingress resource being created.

```yaml
apiVersion: example.com/v1
kind: Application
metadata:
  name: my-app
spec:
  name: my-app
  ingress:
    enabled: true  # Ingress will be created
```
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