k8s.github.io

Configure the load balancer

Now we will install the load balancer that serves as the endpoint for connecting to API server. This will round-robin API server requests between each of the control plane nodes. For this we will use HAProxy in TCP load balancing mode. In this mode it simply forwards all traffic to its back ends (the control planes) without changing it e.g. doing SSL termination.

First, be logged into student-node as directed above.

1. Log into the load balancer

   ssh loadbalancer
   

2. Become root (saves typing sudo before every command)

    sudo -i
   

3. Update the apt package index and install packages needed for HAProxy:

    apt-get update
    apt-get install -y haproxy
   

4. Using the dig command which is an alternative to nslookup and better for scripting with, we can get the private IP addresses of the loadbalancer and 3 control planes.

   dig +short loadbalancer
   dig +short controlplane01
   dig +short controlplane02
   dig +short controlplane03
   

   Terminology

   AWS EC2 instances effectively have two IP addresses:

   1. Private IP - This is the IP on the AWS subnet where the instance is launched, and is used for EC2 instances to talk to each other.
   2. Public IP - Not always assigned, but is the IP used to reach the EC2 instances from the outside world (i.e. your browser). We will see this later in the testing section.

5. Create the HAProxy configuration file

   cat <<EOF > /etc/haproxy/haproxy.cfg
   frontend kubernetes
       bind $(dig +short loadbalancer):6443
       option tcplog
       mode tcp
       default_backend kubernetes-control-nodes
   
   backend kubernetes-control-nodes
       mode tcp
       balance roundrobin
       option tcp-check
       server controlplane01 $(dig +short controlplane01):6443 check fall 3 rise 2
       server controlplane02 $(dig +short controlplane02):6443 check fall 3 rise 2
       server controlplane03 $(dig +short controlplane03):6443 check fall 3 rise 2
   EOF
   

6. Restart and check haproxy

   systemctl restart haproxy
   systemctl status haproxy
   

   It should be warning us that no backend is available - which is true because we haven’t installed Kubernetes yet!

7. Exit from sudo and then back to student-node

   exit
   exit
   

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