➕️ Add ArgoCD advanced content

App of Apps; AppSets

slides/k8s/argocd-advanced.md

@@ -0,0 +1,162 @@
+# ArgoCD advanced patterns
+
+- It's very common to deploy multiple apps or components following the same pattern
+
+- Example: same app deployed to different namespaces (prod, preprod, staging)
+
+- Example: same app deployed to different clusters (same; or regional clusters)
+
+- Example: multiple apps using different Helm charts, each to its own namespace
+
+- Example: multiple apps using the same Helm charts, different values YAML files
+
+- Example: multiple apps deployed to multiple clusters (MxN)
+
+- How should we deal with that?
+
+---
+
+## App of Apps
+
+- ArgoCD Application that contains *more Applications* 
+
+- Typical use-case: deploy a bunch of standard cluster components
+
+  (example: Ingress controller, Prometheus exporters, log collectors, cert-manager...)
+
+- That "App of Apps" can be a Helm chart ([example][argocd-app-of-apps-helm-example])
+
+- It can leverage Helm advanced templating features
+
+  (e.g. iterators, `range`, manipulating files...)
+
+[argocd-app-of-apps-helm-example]: https://argo-cd.readthedocs.io/en/stable/operator-manual/cluster-bootstrapping/#helm-example
+
+---
+
+## Generated Apps, committed to repo
+
+- Write scripts to generate ArgoCD Application manifests from some source of truth
+ 
+  (scripts, more YAML files, database...)
+
+- Commit the generated manifests
+
+- Apply these manifests individually; or with an App of Apps
+
+- Downsides:
+
+  - each new app = need to run scripts, commit new files...
+
+  - lots of potential repetitions in generated manifests
+
+  - changes in the generator = big commit that is harder to analyze and review
+
+---
+
+## Generated Apps, not committed to repo
+
+- What if we generated the ArgoCD Application manifests on the fly?
+
+- This would avoid the downsides mentioned earlier
+
+- But it would require to either:
+
+  - do that in a custom CI/CD pipeline (Jenkins, GitHub Actions...), without ArgoCD
+
+  - or integrate a custom "tool" (YAML generator) into ArgoCD
+
+- *Doable, but quite complex!*
+
+---
+
+## Application Sets
+
+- ArgoCD's native way to generate multiple Apps
+
+- Application Set = ArgoCD Custom Resource containing a `template` and `generators`
+
+- `template` = Application template evaluated with Go templating engine
+
+- `generators` = iterators generating a list of environments
+
+---
+
+## Example
+
+.small[
+```yaml
+apiVersion: argoproj.io/v1alpha1
+kind: ApplicationSet
+metadata:
+  name: my-appset
+spec:
+  goTemplate: true
+  goTemplateOptions: ["missingkey=error"]
+  generators:
+  - list:
+      elements:
+      - repo: frontend
+      - repo: backend
+  template:
+    metadata:
+      name: "{{.repo}}"
+    spec:
+      project: default
+      source:
+        repoURL: "https://github.com/my-org/{{.repo}}.git"
+        targetRevision: main
+        path: deploy/manifests
+      destination:
+        server: "https://kubernetes.default.svc"
+        namespace: "{{.repo}}"
+```
+]
+
+---
+
+## Some generators
+
+- `list` = iterate over a pre-defined list of key/value maps
+
+- `cluster` = deploy app on a list of clusters known to ArgoCD
+
+- `git` = create one app for each file or directory found in a git repo
+
+- `scm` = create one app for each repo detected on GitHub, Gitlab, Gitea, Bitbucket...
+
+- `pullrequest` = ditto, but for pull requests
+
+- `matrix` = combine multiple generators (MxN)
+
+- `merge` = override some parameters
+
+(See [ArgoCD documentation][argocd-generators] for detailed list.)
+
+[argocd-generators]: https://argo-cd.readthedocs.io/en/latest/operator-manual/applicationset/Generators/
+
+---
+
+## Discussion
+
+- Separation of concerns:
+
+  - someone writes code
+  - someone "containerizes" it (e.g. Dockerfiles)
+  - someone writes e.g. Kubernetes manifests or Helm charts
+  - someone deploys Kubernetes clusters
+  - someone installs essential components (observability...)
+  - (maybe someone deploys physical machines, or manages hypervisors)
+  - someone applies Kubernetes manifests to clusters ⭐️
+  - someone is on call on all that
+
+⭐️ That's a part that can be automated with Application Sets.
+
+But it requires someone to define how we organize code, repos, charts...
+
+And some of these tasks will overlap multiple individuals / teams / orgs.
+
+???
+
+:EN:- ArgoCD advanced patterns
+:FR:- Utilisation avancée d'ArgoCD

slides/k8s/argocd.md

@@ -206,7 +206,7 @@ It is responsible for invoking any user-defined hooks for lifecycle events (*Pre
 
 - Let's use the CLI to add an Application:
   ```bash
-    argocd app create kubercoins \ 
+    argocd app create kubercoins \
            --repo https://github.com/`<your_user>/<your_repo>`.git \
            --path . --revision `<branch>` \
            --dest-server https://kubernetes.default.svc \

slides/kube-selfpaced.yml

@@ -133,6 +133,7 @@ content:
   - k8s/gitworkflows.md
   - k8s/flux.md
   - k8s/argocd.md
+  - k8s/argocd-advanced.md
 -
   - k8s/logs-centralized.md
   - k8s/prometheus.md