HA for kubeapi-load-balancer

The standard deployment of Charmed Kubernetes includes a single instance of the kube-api-loadbalancer. For many use cases this is perfectly adequate, but in a production environment you should be keen to eliminate any single point of failure.

The recommended way to provide a failover for the kube-api-loadbalancer is by using keepalived. This is available as a Juju charm and can be deployed into your Charmed Kubernetes model and configured as follows:

  1. Deploy the keepalived charm:

     juju deploy cs:~containers/keepalived
    
  2. Add the required relations :

     juju add-relation keepalived:juju-info kubeapi-load-balancer:juju-info
     juju add-relation keepalived:lb-sink kubeapi-load-balancer:website
     juju add-relation keepalived:loadbalancer kubernetes-master:loadbalancer
     juju add-relation keepalived:website kubernetes-worker:kube-api-endpoint
    

    This redirects both the Kubernetes master and worker units to point at the keepalived service rather than the api-endpoint directly.

  3. Configure the keepalived application. You should substitute a suitable IP address and FQDN in the example below:

     export VIP_HOSTNAME=test.example.com
     juju config keepalived virtual_ip=10.10.74.250
     juju config keepalived port=443
     juju config keepalived vip_hostname=$VIP_HOSTNAME
    
  4. Add the new hostname to the API server certificate. This is done by specifying an additional SAN:

    juju config kubeapi-load-balancer extra_sans=$VIP_HOSTNAME
    juju config kubernetes-master extra_sans=$VIP_HOSTNAME
    
  5. Wait for the new service to settle. You can check the status of the keepalived application by running:

     juju status keepalived
    

    Once the application reports a 'ready' status, continue to the next step.

  6. Remove unneeded relations:

     juju remove-relation kubernetes-worker:kube-api-endpoint kubeapi-load-balancer:website
     juju remove-relation kubernetes-master:loadbalancer kubeapi-load-balancer:loadbalancer
    
  7. Scale up the kubeapi-load-balancer. You can specify as many units as your situation requires. In this example, we add two additional units for a total of three:

     juju add-unit kubeapi-load-balancer -n 2
    

Note that the keepalived application is a subordinate charm - it does not require a machine of its own to run on, but rather runs alongside the kubeapi-load-balancer charm. If for any reason you need to view logs or troubleshoot this application, it will be found co-located on the machines running the load balancer.

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