Add examples of managing strimzi-kafka using argocd

docs/_index.md

@@ -5,4 +5,5 @@ title = 'GitOps'
 This is the documentation for using GitOps to manage Strimzi-based event-driven infrastructure.
 
 - [Introduction to GitOps](introduction/_index.md) — Why GitOps over ClickOps, core concepts, and common technologies.
+- [Kafka Examples](kafka-examples/_index.md) — Bootstrap, infrastructure, and scenario deployment guide.
 

docs/kafka-examples/_index.md

@@ -0,0 +1,177 @@
++++
+title = 'Deploying Kafka with ArgoCD'
++++
+
+The [introduction](../introduction/_index.md) covered why GitOps matters.
+This document shows what it looks like in practice — deploying Apache Kafka infrastructure entirely through ArgoCD, from operators to running clusters.
+
+## How deployment works
+
+Everything in this repository is an ArgoCD Application.
+An Application tells ArgoCD: "watch this directory in Git, and keep the cluster in sync with what's there."
+
+When you apply an Application, ArgoCD reads the Kustomize manifests from the specified directory, renders them, and creates the Kubernetes resources.
+If someone changes a file in the repository, ArgoCD detects the change and updates the cluster.
+If someone changes something directly on the cluster, ArgoCD detects the drift and corrects it.
+
+This means the Git repository is always the source of truth.
+There is no need to run `kubectl apply` on individual manifests, no scripts to remember, no runbooks to follow.
+
+## The deployment flow
+
+The only manual step is installing ArgoCD itself.
+After that, every operator and every Kafka scenario is deployed by applying a single YAML file — the ArgoCD Application.
+
+1. **Install ArgoCD** (manual, one-time) — `kubectl apply -k`
+2. **Deploy operators** — one `kubectl apply -f application.yaml` per operator (Strimzi, Keycloak, ESO)
+3. **Deploy scenarios** — one `kubectl apply -f application.yaml` per scenario (basic-kafka, kafka-mirror, kafka-oauth)
+
+Or skip steps 2 and 3 entirely and deploy everything at once with the app-of-apps ApplicationSet.
+
+### Step 1: ArgoCD bootstrap
+
+ArgoCD is the one component that can't deploy itself.
+The `examples/argo-cd/` directory contains Kustomize overlays for OpenShift and Kubernetes.
+
+On OpenShift, the install is two steps — the operator and then the instance:
+
+```bash
+kubectl apply -k examples/argo-cd/overlays/openshift/operator
+kubectl apply -k examples/argo-cd/overlays/openshift/instance
+```
+
+The OpenShift overlay includes two important configurations:
+- `ARGOCD_CLUSTER_CONFIG_NAMESPACES=argocd` on the operator subscription, which grants the ArgoCD instance cluster-scope permissions.
+- A `streamshub` AppProject with `clusterResourceWhitelist`, which allows ArgoCD to manage cluster-scoped resources like Namespaces.
+
+On Kubernetes:
+
+```bash
+kubectl apply -k examples/argo-cd/overlays/kubernetes
+```
+
+### Step 2: Deploy operators
+
+Each operator has an ArgoCD Application file.
+Applying it tells ArgoCD to install and manage the operator.
+
+For example, deploying the Strimzi operator on OpenShift:
+
+```bash
+kubectl apply -f examples/operators/strimzi/overlays/streams-for-kafka/argocd/application.yaml
+```
+
+That single command creates the namespace, the OLM Subscription, the OperatorGroup, and starts the operator.
+ArgoCD keeps it in sync — if someone accidentally deletes the Subscription, ArgoCD recreates it.
+
+The same pattern works for every operator:
+
+```bash
+# Keycloak / RHBK (needed for the OAuth scenario)
+kubectl apply -f examples/operators/keycloak/overlays/rhbk/argocd/application.yaml
+
+# External Secrets Operator (needed for the mirror scenario)
+kubectl apply -f examples/operators/external-secrets/overlays/openshift/argocd/application.yaml
+```
+
+### Step 3: Deploy scenarios
+
+Scenarios work exactly the same way — each is an ArgoCD Application:
+
+```bash
+kubectl apply -f examples/scenarios/basic-kafka/argocd/application.yaml
+```
+
+ArgoCD creates the namespace, deploys the Kafka cluster, node pools, metrics configuration, and all supporting resources.
+The Strimzi operator then takes over and creates the actual broker and controller pods.
+
+### Deploying everything at once
+
+Instead of applying Applications one by one, the app-of-apps pattern deploys all operators and scenarios with a single command.
+The ApplicationSet uses a combination of a list generator (for operators) and a Git directory generator (for scenarios):
+
+```bash
+# OpenShift with Streams for Apache Kafka + RHBK
+kubectl apply -f examples/app-of-apps/overlays/openshift/applicationset.yaml
+
+# Kubernetes with community Strimzi + Keycloak
+kubectl apply -f examples/app-of-apps/overlays/kubernetes/applicationset.yaml
+```
+
+Adding a new scenario directory under `examples/scenarios/` automatically creates a new ArgoCD Application on the next sync.
+
+## What the scenarios deploy
+
+### Basic Kafka
+
+A single Kafka cluster in KRaft mode with three controllers and three brokers.
+Includes Cruise Control for automatic rebalancing, Entity Operator for managing topics and users as custom resources, and JMX Prometheus metrics.
+
+Two listeners: plain-text on port 9092 and TLS with client certificate authentication on port 9093.
+
+### Kafka Mirror
+
+Two independent Kafka clusters with MirrorMaker 2 replicating all topics from source to target.
+
+This scenario demonstrates a practical Kubernetes challenge: MirrorMaker 2 runs in the `kafka-target` namespace but needs TLS credentials from `kafka-source`.
+The External Secrets Operator solves this by automatically syncing secrets between namespaces.
+A `SecretStore` reads from `kafka-source`, and `ExternalSecret` resources pull the CA certificate and user credentials into `kafka-target`.
+If the source cluster rotates its CA certificate, the change propagates automatically.
+
+### Kafka OAuth
+
+A complete OAuth 2.0 setup: Keycloak as the OIDC provider with a Kafka-specific realm, and a Kafka cluster with token-based authentication on the TLS listener.
+
+Strimzi v1 replaced the built-in `type: oauth` listener with `type: custom`.
+The OAuth libraries remain bundled in the Kafka images — only the API changed.
+The JAAS configuration tells Kafka to validate JWT tokens against Keycloak's JWKS endpoint.
+
+The Keycloak operator is installed into the `keycloak` namespace, and the Keycloak instance is deployed in the same namespace.
+This is important because the Keycloak operator watches only its own namespace by default.
+
+The realm includes test users and OAuth clients.
+You can test the setup using [strimzi/test-clients](https://github.com/strimzi/test-clients) Jobs that authenticate via client credentials flow.
+
+## Making changes
+
+The power of this setup is what happens after the initial deployment.
+
+### Scaling brokers
+
+To add a broker, change `replicas: 3` to `replicas: 4` in `brokers.yaml`, commit, and push.
+ArgoCD detects the change, updates the KafkaNodePool, and Strimzi creates the new broker pod.
+Cruise Control automatically rebalances partitions to include the new broker.
+
+### Updating configuration
+
+To change a Kafka setting like retention time, edit `kafka.yaml`, commit, and push.
+ArgoCD syncs the change, and the Strimzi operator performs a rolling restart of the brokers.
+
+### Adding a new scenario
+
+Create a new directory under `examples/scenarios/` with a `kustomization.yaml` and the Kafka resources.
+If you're using the app-of-apps ApplicationSet, ArgoCD automatically discovers it and creates a new Application.
+
+## Community and product support
+
+All scenarios use the `kafka.strimzi.io/v1` CRD API, which is identical for both the community project and the commercial product.
+The only difference is which operator you install.
+
+| Component | Community | Product |
+|-----------|-----------|---------|
+| Kafka operator | Strimzi | Streams for Apache Kafka (`amq-streams`) |
+| Identity provider | Keycloak | Red Hat Build of Keycloak (`rhbk-operator`) |
+| Secret management | ESO (Helm chart) | ESO for Red Hat OpenShift (`openshift-external-secrets-operator`) |
+
+Switching between community and product is a matter of deploying a different operator Application.
+The scenarios themselves don't change.
+
+## What's next
+
+These scenarios cover the foundational Kafka patterns.
+Future additions could include:
+
+- **KafkaConnect with Debezium** for change data capture
+- **StreamsHub Console** for Kafka cluster management UI
+- **Kroxylicious** for Kafka proxy with encryption and schema enforcement
+- **Monitoring** with Prometheus and Grafana dashboards

examples/app-of-apps/README.md

@@ -0,0 +1,58 @@
+# App-of-Apps Pattern
+
+An ArgoCD ApplicationSet that deploys all infrastructure operators and scenarios from this repository with a single command.
+
+## Platform-Specific Variants
+
+Since infrastructure operators differ between platforms (OLM on OpenShift vs upstream manifests on Kubernetes), there are platform-specific ApplicationSets:
+
+- `overlays/openshift/` — deploys Streams for Apache Kafka, RHBK, ESO (Red Hat), and all scenarios
+- `overlays/kubernetes/` — deploys community Strimzi, Keycloak, and all scenarios
+
+## Quick Start
+
+### OpenShift
+
+```bash
+kubectl apply -f overlays/openshift/applicationset.yaml
+```
+
+### Kubernetes
+
+```bash
+kubectl apply -f overlays/kubernetes/applicationset.yaml
+```
+
+## What Gets Deployed
+
+### OpenShift
+
+| Application | Path |
+|-------------|------|
+| `streams-for-kafka-operator` | `operators/strimzi/overlays/streams-for-kafka` |
+| `rhbk-operator` | `operators/keycloak/overlays/rhbk` |
+| `external-secrets-operator` | `operators/external-secrets/overlays/openshift` |
+| `basic-kafka` | `scenarios/basic-kafka` |
+| `kafka-mirror` | `scenarios/kafka-mirror` |
+| `kafka-oauth` | `scenarios/kafka-oauth` |
+
+### Kubernetes
+
+| Application | Path |
+|-------------|------|
+| `strimzi-operator` | `operators/strimzi/overlays/kubernetes` |
+| `keycloak-operator` | `operators/keycloak/overlays/kubernetes` |
+| `basic-kafka` | `scenarios/basic-kafka` |
+| `kafka-mirror` | `scenarios/kafka-mirror` |
+| `kafka-oauth` | `scenarios/kafka-oauth` |
+
+## Selective Deployment
+
+To deploy only specific components, modify the `generators` section:
+- Remove entries from the `list` generator to skip specific operators
+- Add `exclude` entries to the `git` generator to skip specific scenarios
+
+## Prerequisites
+
+- ArgoCD installed (see [ArgoCD installation](../argo-cd/))
+- The `streamshub` AppProject must exist (created as part of the ArgoCD instance setup)

examples/app-of-apps/overlays/kubernetes/applicationset.yaml

@@ -0,0 +1,48 @@
+apiVersion: argoproj.io/v1alpha1
+kind: ApplicationSet
+metadata:
+  name: streamshub-gitops
+  namespace: argocd
+spec:
+  goTemplate: true
+  goTemplateOptions: ["missingkey=error"]
+  generators:
+    - list:
+        elements:
+          - name: strimzi-operator
+            path: examples/operators/strimzi/overlays/kubernetes
+            namespace: strimzi-operator
+          - name: keycloak-operator
+            path: examples/operators/keycloak/overlays/kubernetes
+            namespace: keycloak
+    - git:
+        repoURL: https://github.com/streamshub/streamshub-gitops.git
+        # TODO: switch back to HEAD before merge
+        revision: argocd-kafka-examples
+        directories:
+          - path: examples/scenarios/*
+  template:
+    metadata:
+      name: '{{ default .path.basename .name }}'
+      labels:
+        app.kubernetes.io/part-of: streamshub-gitops
+    spec:
+      project: streamshub
+      source:
+        repoURL: https://github.com/streamshub/streamshub-gitops.git
+        # TODO: switch back to HEAD before merge
+        targetRevision: argocd-kafka-examples
+        path: '{{ default .path .path.path }}'
+      destination:
+        server: https://kubernetes.default.svc
+        namespace: '{{ default "" .namespace }}'
+      syncPolicy:
+        automated:
+          prune: false
+          selfHeal: true
+        managedNamespaceMetadata:
+          labels:
+            argocd.argoproj.io/managed-by: argocd
+        syncOptions:
+          - CreateNamespace=true
+          - ServerSideApply=true

examples/app-of-apps/overlays/openshift/applicationset.yaml

@@ -0,0 +1,57 @@
+apiVersion: argoproj.io/v1alpha1
+kind: ApplicationSet
+metadata:
+  name: streamshub-gitops
+  namespace: argocd
+spec:
+  goTemplate: true
+  goTemplateOptions: ["missingkey=error"]
+  generators:
+    - list:
+        elements:
+          - name: streams-for-kafka-operator
+            path: examples/operators/strimzi/overlays/streams-for-kafka
+            namespace: streams-kafka-operator
+          - name: rhbk-operator
+            path: examples/operators/keycloak/overlays/rhbk
+            namespace: keycloak
+          - name: external-secrets-operator
+            path: examples/operators/external-secrets/overlays/openshift
+            namespace: external-secrets-operator
+    - git:
+        repoURL: https://github.com/streamshub/streamshub-gitops.git
+        # TODO: switch back to HEAD before merge
+        revision: argocd-kafka-examples
+        directories:
+          - path: examples/scenarios/*
+  template:
+    metadata:
+      name: '{{ default .path.basename .name }}'
+      labels:
+        app.kubernetes.io/part-of: streamshub-gitops
+    spec:
+      project: streamshub
+      source:
+        repoURL: https://github.com/streamshub/streamshub-gitops.git
+        # TODO: switch back to HEAD before merge
+        targetRevision: argocd-kafka-examples
+        path: '{{ default .path .path.path }}'
+      destination:
+        server: https://kubernetes.default.svc
+        namespace: '{{ default "" .namespace }}'
+      syncPolicy:
+        automated:
+          prune: false
+          selfHeal: true
+        managedNamespaceMetadata:
+          labels:
+            argocd.argoproj.io/managed-by: argocd
+        syncOptions:
+          - CreateNamespace=true
+          - SkipDryRunOnMissingResource=true
+        retry:
+          limit: 5
+          backoff:
+            duration: 30s
+            maxDuration: 5m
+            factor: 2

examples/argo-cd/overlays/openshift/instance/app-project.yaml

@@ -0,0 +1,14 @@
+apiVersion: argoproj.io/v1alpha1
+kind: AppProject
+metadata:
+  name: streamshub
+  namespace: argocd
+spec:
+  clusterResourceWhitelist:
+    - group: '*'
+      kind: '*'
+  destinations:
+    - namespace: '*'
+      server: '*'
+  sourceRepos:
+    - '*'

examples/infrastructure/argo-cd/overlays/openshift/instance/kustomization.yaml → examples/argo-cd/overlays/openshift/instance/kustomization.yaml

@@ -4,3 +4,4 @@ kind: Kustomization
 resources:
   - namespace.yaml
   - argocd.yaml
+  - app-project.yaml

examples/infrastructure/argo-cd/overlays/openshift/operator/subscription.yaml → examples/argo-cd/overlays/openshift/operator/subscription.yaml

@@ -9,3 +9,7 @@ spec:
   name: openshift-gitops-operator
   source: redhat-operators
   sourceNamespace: openshift-marketplace
+  config:
+    env:
+      - name: ARGOCD_CLUSTER_CONFIG_NAMESPACES
+        value: argocd