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Kubernetes LB health check documentation questions

Posted December 4, 2019 446 views
DigitalOcean Managed Kubernetes

I noticed that in the documentation https://www.digitalocean.com/docs/kubernetes/how-to/configure-load-balancers/ the following statement is made

By default, the load balancer performs health checks on the worker nodes over HTTP on port 80 at the webserver root.

However, when I look at the LB configuration UI for a K8s cluster, it is set to tcp://0.0.0.0:30666

Which should it be? What if the scheduler puts all of the pods that respond to http on only one node? It seems like this default rule would direct traffic to a node that couldn’t serve it?

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scottmiller
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jkwiatkoski December 4, 2019

Hi there,

What youre seeing there is a nodeport that is where the LB checks the health on the node. If you use kubectl to describe the pertinent service you will see that this 30666 nodeport translates to a different container port (probably 80).

kubectl describe svc <service_name> give output like this:

…
Port: http 80/TCP
TargetPort: http/TCP
NodePort: http 30541/TCP
…

In my example the LB reaches the node on port 30541 but that traffic actually hits the container on port 80. That is what is meant by that sentence.

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