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A cluster for KubeFlex hosting#

This document tells you what makes a Kubernetes cluster suitable to serve as the KubeFlex hosting cluster and shows some ways to create such a cluster.

Requirements on the KubeFlex hosting cluster#

The KubeFlex hosting cluster needs to run an Ingress controller with SSL passthrough enabled.

Connectivity from clients#

The clients in KubeStellar need to be able to open a TCP connection to where the Ingress controller is listening for HTTPS connections.

The clients in KubeStellar comprise the following.

  • The OCM Agent and the OCM Status Add-On Agent in each WEC.
  • The KubeStellar controller-manager and the transport controller for each WDS, running in the KubeFlex hosting cluster.

TODO: finish writing this subsection for real. Following are some clues.

When everything runs on one machine, the defaults just work. When core and some WECs are on different machines, it gets more challenging. When the KubeFlex hosting cluster is an OpenShift cluster with a public domain name, the defaults just work.

After the quickstart setup, I looked at an OCM Agent (klusterlet-agent, to be specific) and did not find a clear passing of kubeconfig. I found adjacent Secrets holding kubeconfigs in which cluster[0].cluster.server was https://kubeflex-control-plane:31048. Note that kubeflex-control-plane is the name of the Docker container running kind cluster serving as KubeFlex hosting cluster. I could not find an explanation for the port number 31048; that Docker container maps port 443 inside to 9443 on the outside.

kflex init takes a command line flag --domain string described as domain for FQDN (default "").

Creating a hosting cluster#

Following are some ways to create a Kubernetes cluster that is suitable to use as a KubeFlex hosting cluster. This is not an exhaustive list.

Create and init a kind cluster as hosting cluster with kflex#

The following command will use kind to create a cluster with an Ingress controller with SSL passthrough AND ALSO proceed to install the KubeFlex implementation in it and set your current kubeconfig context to access that cluster as admin.

kflex init --create-kind

Create and init a kind cluster as hosting cluster with curl-to-bash script#

There is a bash script at that can be fed directly into bash and will create a kind cluster AND ALSO initialize it as the KubeFlex hosting cluster. This script accepts the following command line flags.

  • --name name: set a specific name of the kind cluster (default: kubestellar).
  • --port port: map the specified host port to the kind cluster port 443 (default: 9443).
  • --nowait: when given, the script proceeds without waiting for the nginx ingress patching to complete.
  • --nosetcontext: when given, the script does not change the current kubectl context to the newly created cluster.
  • -X enable verbose execution of the script for debugging.

Create a k3d cluster#

This has been tested with version 5.6.0 of k3d.

  1. Create a K3D hosting cluster with nginx ingress controller:

    k3d cluster create -p "9443:443@loadbalancer" --k3s-arg "--disable=traefik@server:*" kubeflex
    helm install ingress-nginx ingress-nginx --repo --version 4.6.1 --namespace ingress-nginx --create-namespace

  2. When we use kind, the name of the container is kubeflex-control-plane and that is what we use in the internal URL for --force-internal-endpoint-lookup. Here the name of the container created by K3D is k3d-kubeflex-server-0 so we rename it:

    docker stop k3d-kubeflex-server-0
    docker rename k3d-kubeflex-server-0 kubeflex-control-plane
    docker start kubeflex-control-plane
    Wait 1-2 minutes for all pods to be restarted. Use the following command to confirm all are fully running:
    kubectl --context k3d-kubeflex get po -A

  3. Enable SSL passthrough: We are using nginx ingress with tls passthrough. The current install for kubeflex installs also nginx ingress but specifically for kind. To specify passthrough for K3D, edit the ingress placement controller with the following command and add --enable-ssl-passthrough to the list of arguments for the container

    kubectl edit deployment ingress-nginx-controller -n ingress-nginx