multi-cluster mesh routing /w GitOps

This demo will build you 3 clusters that will all share their routing information with each other and forward DNS for cross-cluster Services.

The clusters are created using kind, and cluster0 is used as a Flux management cluster. Access to apply to the remaining clusters is done by mocking ClusterAPI kubeconfigs.

Discovery of other clusters' Nodes is accomplished through a fun bash controller that queries a multicast Serf cluster. This works well on a single docker network or any network that supports multicast. You can also configure Serf to bootstrap from some fixed IP's.

A neat thing about this strategy is that it's declarative! Fork this repo and try it out :)

Requirements:

1. your computer
2. these tools
   • git
   • hub (optional)
   • flux
   • docker
   • kind
   • kubectl

Let's go

hub clone stealthybox/multicluster-gitops
cd multicluster-gitops
hub fork
  # alternatively fork in the web UI and clone

kind/setup.sh
kind/load.sh

# bootstrap Calico for Flux
kubectl apply --context kind-cluster0 -k ./config/cluster0/kube-system

GITHUB_USER=stealthybox
# set your own user here to match your fork

export GITHUB_TOKEN="<personal access token with repo and SSH key rights>"

flux bootstrap github \
  --owner "${GITHUB_USER}" \
  --personal \
  --repository "multicluster-gitops" \
  --path "./config/cluster0"

alternatively, if you want to not use github & flux, apply the kube-system and default kustomizations to the proper clusters:

for cl in cluster{0..2}; do
  kubectl apply --context "kind-${cl}" -k "./config/${cl}/"{default,kube-system}
done

Looking around

• Get the Kustomization resources the cluster0 flux-system uses to apply to the other clusters
• Use the kubectl --context flag to switch between kind-cluster0|1|2 on demand
• Check that the serf and calico dameonsets and deploys become ready
• Check out the Corefile ConfigMap extensions in kube-system
• Examine the BGPPeer resources that the serf-query controller created from the serf member list
• Exec into the debug pods for each cluster and run host podinfo.default.svc.cluster1.lan
• Try curling the service from and to different clusters!

Tidying Up

kind/cleanup.sh

More demos!

Check out this next demo featuring Flux's GPG signature verification and remote-cluster management over Cluster API: stealthybox/capi-flux-demo