Originally published on the Google Cloud Community blog at https://medium.com/google-cloud/internal-load-balancing-for-kubernetes-services-on-google-cloud-f8aef11fb1c4
As discussed in my recent post on kubernetes ingress there is really only one way for traffic from outside your cluster to reach services running in it. You can read that article for more detail but the tl;dr is that all outside traffic gets into the cluster by way of a nodeport, which is a port opened on every host/node. Nodes are ephemeral things and clusters are designed to scale up and down, and because of this you will always need some sort of load balancer between clients and the nodeports. If you’re running on a cloud platform like GKE then the usual way to get there is to use a type LoadBalancer service or an ingress, either of which will build out a load balancer to handle the external traffic.
This isn’t always, or even most often what you want. Your case may vary but at Olark we deploy a lot more internal services than we do external ones. Up until recently the load balancers created by kubernetes on GKE were always externally visible, i.e. they were allocated a non-private IP that is reachable from outside the project. Maintaining firewall rules to sandbox lots of internal services is not a tradeoff we want to make, so for these use cases we created our services as type NodePort, and then provisioned an internal TCP load balancer for them using terraform.Continue reading