Make prometheus install for a fresh user

[malcolmholmes]

Previously, a change was made to make it possible to have multiple Prometheus servers running. This involved two changes: putting everything into a prometheus wrapper element, and then making that element hidden.

The issue is that, for a new user, this introduces a weird behaviour. You get Grafana installed, but no Prometheus. And the reason, for a new Jsonnet user is esoteric: :: vs :.

This PR keeps all Prometheus resources inside the new element - this seems like a good practice, as it allows that element to be referenced and cloned, as was the intent of the original change.

However, it makes the prometheus element public. That way, newcomers will get the Prometheus server they expect. More experienced users, who want to set up multiple Prometheus servers, can do prometheus:: $.prometheus, which will hide the prometheus node.

[woodsaj]

We dont need to revert this change here. With our internal usage of prometheus-ksonnet we have the following:

  // We don't want to deploy main_prometheus, but we can't hide it in
  // prometheus-ksonnet or we'd break other peoples deployments.
  main_prometheus: {},

So, looks like the issue here is simply that main_prometheus is not defined. So perhaps we just add it.
eg in prometheus.libsonnet just add the following at the bottom.

  main_prometheus: $.prometheus {name: "prometheus"},

[cstyan]

Came here to say the same thing as @woodsaj. I don't think this is the correct solution unless there were a way to enforce that name is unique for each Prometheus.

In this PR (#156) I claim to have made deployment of Prometheus replicas as a statefulset the default, but clearly I didn't add the actual replicas.

Re adding main_prometheus should work.

main_prometheus: $.prometheus {
    name: 'prometheus',
},

[cstyan]

re-add main_prometheus and double check that that doesn't result in the addition of a third Prometheus instance in one of our clusters

[malcolmholmes]

@cstyan Thanks. I feel better now - the main_prometheus thing makes sense of the history.

I'd say that my fix and the main_prometheus one achieve basically the same thing, but I'm happy to go with the original intent. Will fix tomorrow.

[malcolmholmes]

@cstyan switched to your main_prometheus fix. Approved?

[cstyan]

awesome 👍