Hosting Your Own Kubernetes NodePort Load Balancer

Posted on 11 Jan 2016 by Eric Oestrich

I recently switched from using a regular Loadbalancer in kubernetes to using a NodePort load balancer. I switched because I wanted to get away from using the fairly expensive network load balancer in Google Cloud Compute in a personal project.

I did this by creating a new service for nginx inside of the cluster, and setting it to use a NodePort load balancer. Then creating a micro instance that hosts another nginx that proxies to the private IPs of the cluster nodes.

nginx-service
apiVersion: v1
kind: Service
metadata:
  name: nginx
  labels:
    name: nginx
spec:
  type: NodePort
  ports:
    - port: 80
      nodePort: 30080
      name: http
    - port: 443
      nodePort: 30443
      name: https
  selector:
    name: nginx

The import pieces here are type and the nodePort line inside of ports. This will cause kubernetes to listen on 30080 and 30443 respectively. This port has to be between the range of 30000-32767.

Once the service is defined as a NodePort load balancer you need to set up the micro instance.

/etc/nginx/sites-enabled/example
upstream example-https {
  server 10.0.0.1:30443; # private node ip
  server 10.0.0.2:30443; # private node ip
}

server {
  # ... ssl setup ...

  location / {
    # ... proxy_pass configuration ...
    proxy_pass https://example-https;
  }

  # ... other nginx setup ...
}

Here we have a stripped down sample file sites-enabled/example that nginx will load and start serving. I have SSL set up and proxy_pass to the private IP of each kubernetes node. I do keep SSL between this front nginx and the nginx inside of the cluster.

There isn't anything special about this file so I've stripped out the unimportant pieces. You can see a more complete example of my nginx files in the post hosting nginx in docker.

Drawbacks

There are a few drawbacks using this approach. I've had at least once the private IP change (I think the nodes rebooted themselves after a crash) and I had to update this frontend nginx. You also have to manually add in an new nodes. The normal load balancer would have handled each case for me.

Overall I've been happy with this setup. It was nice to see that kubernetes let me handle my own external load balancing.

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