In-cluster config support

[hekike]

Hi,

would you be open for adding a built-in in-cluster config?

Based on:
https://github.com/kubernetes/client-go/blob/124670e99da15091e13916f0ad4b2b2df2a39cd5/rest/config.go#L274
and
http://kubernetes.io/docs/user-guide/accessing-the-cluster/#accessing-the-api-from-a-pod

Something like:

const fs = require('fs')

const certPath = '/var/run/secrets/kubernetes.io/serviceaccount/ca.crt'
const tokenPath = '/var/run/secrets/kubernetes.io/serviceaccount/token'
const namespacePath = '/var/run/secrets/kubernetes.io/serviceaccount/namespace'

function getInClusterConfig () {
  const host = process.env.KUBERNETES_SERVICE_HOST
  const port = process.env.KUBERNETES_SERVICE_PORT
  let cert
  let namespace
  let bearer

  if (!host || !port) {
    throw TypeError('Unable to load in-cluster configuration, KUBERNETES_SERVICE_HOST and KUBERNETES_SERVICE_PORT must be defined')
  }

  try {
    cert = fs.readFileSync(certPath, 'utf8')
  } catch (err) {
    throw TypeError('Expected to load root CA config from ${certPath}, but got err', err)
  }

  try {
    bearer = fs.readFileSync(tokenPath, 'utf8')
  } catch (err) {
    throw TypeError('Expected to load token config from ${tokenPath}, but got err', err)
  }

  try {
    namespace = fs.readFileSync(namespacePath, 'utf8')
  } catch (err) {
    throw TypeError('Expected to load namespace config from ${namespacePath}, but got err', err)
  }

  return {
    url: `https://${host}:${port}`,
    cert,
    auth: { bearer },
    namespace
  }
}

The interface could be:

const K8Api = require('kubernetes-client');
const k8 = new K8Api.Core(K8Api.getInClusterConfig())

I'm happy to send a PR if you like the idea.
What do you think?

[silasbw]

Yeah, I like this idea. I PR would be much appreciated.

@jcrugzz any thoughts?

[jcrugzz]

Yea this seems super convenient 👍. Would definitely take a PR