Summary - Multi-cluster

Combine kubeconfig and cross-cluster service to switch contexts.

Summary: multi-cluster

In this group:

Multiple clusters are used for isolation, availability, regulation and scale; the cost is operational load.
Distribution: GitOps (Argo CD ApplicationSet, Flux) or managers like Karmada; KubeFed was abandoned.
Kubeconfig: clusters + users + contexts; --context, KUBECONFIG merging, exec-based credentials.
Cross-cluster services: MCS (ServiceExport, clusterset.local), a mesh or an internal LB; CIDRs must not overlap.
A cluster registry is a set of labelled records; the ApplicationSet cluster generator deploys by label.

for c in uretim-eu uretim-tr; do kubectl --context $c get deploy -n magaza; done

Exercise Checking all clusters

Write a one-line shell loop: for c in uretim-eu uretim-tr; do kubectl --context $c get deploy -n magaza; done. Then, on a separate line, print the ready replica count of the api deployment in magaza in the uretim-tr context with jsonpath='{.status.readyReplicas}'.

Show example solution

for c in uretim-eu uretim-tr; do kubectl --context $c get deploy -n magaza; done
kubectl --context uretim-tr get deploy api -n magaza -o jsonpath='{.status.readyReplicas}'

Test yourself

What is a good way to reduce the risk of running a command on the wrong cluster?
- Giving the clusters the same name
- Writing --context explicitly on every command in scripts
- Sharing a single kubeconfig
- Relying on current-context
Show answer

Writing --context explicitly on every command in scripts — The active context may have been changed in another terminal.

Run the command on a specific cluster.

kubectl ____ uretim-tr get pods -n magaza

Show answer

kubectl --context uretim-tr get pods -n magaza

Match.

--context

Single-command target
ApplicationSet

Multi-cluster deployment
ServiceExport

Cross-cluster service
kubeconfig

Connection info

Next lesson: What is OPA?

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