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I have set up an experimental local Kubernetes cluster with one master and three slave nodes. I have created a deployment for a custom service that listens on port 10001. The goal is to access an exemplary endpoint /hello with a stable IP/hostname, e.g. http://<master>:10001/hello.

After deploying the deployment, the pods are created fine and are accessible through their cluster IPs.

I understand the solution for cloud providers is to create a load balancer service for the deployment, so that you can just expose a service. However, this is apparently not supported for a local cluster. Setting up Ingress seems overkill for this purpose. Is it not?

It seems more like kube proxy is the way to go. However, when I run kube proxy --port <port> on the master node, I can access http://<master>:<port>/api/..., but not the actual pod.

There are many related questions (e.g. How to access services through kubernetes cluster ip?), but no (accepted) answers. The Kubernetes documentation on the topic is rather sparse as well, so I am not even sure about what is the right approach conceptually.

I am hence looking for a straight-forward solution and/or a good tutorial. It seems to be a very typical use case that lacks a clear path though.

Carsten
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2 Answers2

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If an Ingress Controller is overkill for your scenario, you may want to try using a service of type NodePort. You can specify the port, or let the system auto-assign one for you.

A NodePort service exposes your service at the same port on all Nodes in your cluster. If you have network access to your Nodes, you can access your service at the node IP and port specified in the configuration.

Obviously, this does not load balance between nodes. You can add an external service to help you do this if you want to emulate what a real load balancer would do. One simple option is to run something like rocky-cli.

Kekoa
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  • Already having an external HAProxy for load balancing, this seems the smoothest solution in my scenario. However, the nodes remain blocked from outside requests even after adding an iptables rule (I can access them via their external IP from inside the machine though): `iptables -A INPUT -p tcp --dport -j ACCEPT` Any clues on that? – Carsten Jun 13 '17 at 11:55
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An Ingress is probably your simplest bet.

You can schedule the creation of an Nginx IngressController quite simply; here's a guide for that. Note that this setup uses a DaemonSet, so there is an IngressController on each node. It also uses the hostPort config option, so the IngressController will listen on the node's IP, instead of a virtual service IP that will not be stable.

Now you just need to get your HTTP traffic to any one of your nodes. You'll probably want to define an external DNS entry for each Service, each pointing to the IPs of your nodes (i.e. multiple A/AAAA records). The ingress will disambiguate and route inside the cluster based on the HTTP hostname, using name-based virtual hosting.

If you need to expose non-HTTP services, this gets a bit more involved, but you can look in the nginx ingress docs for more examples (e.g. UDP).

Symmetric
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