Docker & Kubernetes
Cluster registry
Learn the cluster registry concept.
Cluster registry
On a multi-cluster platform, the question "which clusters exist, where, at which version, which environment" must have a single answer: a cluster registry (inventory). In Argo CD, clusters are kept as labelled Secrets; the ApplicationSet's cluster generator deploys by these labels:
apiVersion: v1
kind: Secret
metadata:
name: uretim-tr
namespace: argocd
labels:
argocd.argoproj.io/secret-type: cluster
ortam: uretim
bolge: tr
stringData:
name: uretim-tr
server: https://tr.k8s.sirket.com
Deploying by label
The ApplicationSet cluster generator produces an Application for each registered cluster matching the labels:
spec:
generators:
- clusters:
selector:
matchLabels:
ortam: uretim
template:
metadata:
name: 'magaza-{{name}}'
spec:
destination:
server: '{{server}}'
namespace: magaza
That way which application runs on which clusters is documented in Git and in the labels.
Exercise A cluster record
Write a Secret YAML: name uretim-tr, namespace argocd; labels argocd.argoproj.io/secret-type: cluster, ortam: uretim; under stringData, name: uretim-tr and server: https://tr.k8s.sirket.com.
Show example solution
apiVersion: v1
kind: Secret
metadata:
name: uretim-tr
namespace: argocd
labels:
argocd.argoproj.io/secret-type: cluster
ortam: uretim
stringData:
name: uretim-tr
server: https://tr.k8s.sirket.com
Test yourself
-
What is the benefit of the cluster generator's label selector?
- It encrypts labels
- It isn't needed
- When a new production cluster is labelled, applications are deployed to it automatically
- It deletes clusters
Show answer
When a new production cluster is labelled, applications are deployed to it automatically — Adding a cluster becomes the same as adding a Secret.
-
Mark the Secret as an Argo CD cluster record.
labels:
argocd.argoproj.io/secret-type: ____
Show answer
labels:
argocd.argoproj.io/secret-type: cluster
-
Match.
- cluster registration
- Inventory
- secret-type: cluster
- Argo CD cluster
- clusters generator
- Deploy by label
- {{server}}
- Cluster address
Next lesson: Summary - Multi-cluster
