Mastering Kubernetes - Second Edition

Utilizing the NodePort

Each service will be allocated a dedicated port from a predefined range. This usually is a high range, such as 30,000 and above, to avoid clashing with other applications using low known ports. HAProxy will run outside the cluster in this case, and it will be configured with the correct port for each service. Then it can just forward any traffic to any nodes and Kubernetes through the internal service, and the load balancer will route it to a proper pod (double load balancing). This is, of course, sub-optimal because it introduces another hop. The way to circumvent it is to query the Endpoints API and dynamically manage for each service the list of its backend pods and directly forward traffic to the pods.