fix: use address 0.0.0.0 in Kubernetes env (#579)

[sinedied]

Checklist

• run npm run test and npm run benchmark
• tests and/or benchmarks are included
• documentation is changed or added
• commit message and code follows the Developer's Certification of Origin
  and the Code of conduct

This PR adds a check so that it automatically use 0.0.0.0 when running inside a Kubernetes environment.

[climba03003]

I still in favor of multiple methods for the detection.

For example, different cloud platform may result in derivation of behavior which means that this environment variables are not always set.
https://stackoverflow.com/questions/66470062/aks-not-creating-kubernetes-service-host-and-kubernetes-service-port-environment

[climba03003]

A proper implementation should be follow kubectl check.

By default kubectl will first determine if it is running within a pod, and thus in a cluster. It starts by checking for the KUBERNETES_SERVICE_HOST and KUBERNETES_SERVICE_PORT environment variables and the existence of a service account token file at /var/run/secrets/kubernetes.io/serviceaccount/token. If all three are found in-cluster authentication is assumed.

To maintain backwards compatibility, if the POD_NAMESPACE environment variable is set during in-cluster authentication it will override the default namespace from the service account token. Any manifests or tools relying on namespace defaulting will be affected by this.

We are not authenticating for in-cluster but the method is good for environment detection.

[mcollina]

lgtm

[sinedied]

A proper implementation should be follow kubectl check.

By default kubectl will first determine if it is running within a pod, and thus in a cluster. It starts by checking for the KUBERNETES_SERVICE_HOST and KUBERNETES_SERVICE_PORT environment variables and the existence of a service account token file at /var/run/secrets/kubernetes.io/serviceaccount/token. If all three are found in-cluster authentication is assumed.

To maintain backwards compatibility, if the POD_NAMESPACE environment variable is set during in-cluster authentication it will override the default namespace from the service account token. Any manifests or tools relying on namespace defaulting will be affected by this.

We are not authenticating for in-cluster but the method is good for environment detection.

Good point, I'll update the PR with the additional check. I was looking for something similar in the docs, but couldn't find it 🙂