support carbonapi

[tbauriedel]

This PR not only adds support for carbonapi, it supports graphite-api which implements API version 0.9.8 and carbonapi which implements the necessary endpoints of API version 1.11.7 (and not metrics/expand).

Endpoint Documentation:

• graphite-web
• graphite-api
• carbonapi

I have tested it with the latest available graphite-api and carbonapi v0.16.0

Possible solution for #300

Feedback welcome!

CC @dgoetz

[widhalmt]

Tested it in my environment as well. Works flawlessly so far. THANK YOU!

[citfs]

It also works perfectly in our environment. Thank you very much.

[nilmerg]

Just to be sure, this keeps 100% compatibility with how it worked before?

[tbauriedel]

We use another API endpoint now. The return of the API is a little bit different, which is why the data is stored slightly differently into the results.

Based on the API endpoint documentations that will work with all possible components.
As mentioned: It is only tested on graphite-api and carbonapi. I had no graphite-web to test it there also. Based on the documentation it should work there also.

Besides of that it works how it worked before.

Long story short:
It was possible for me and others to switch from graphite-api to carbonapoi without changing anything on the module.
Drop-in replacement.

[tbauriedel]

While working on another topic for the module I have found a difference that will break the current behaviour.

The changes merge graphs with placeholders into one * and only one graph is rendered.
(Also in the graphite-api)
I'll take another look at the whole thing in detail and try to adapt it accordingly.

Please wait for that before merging!

Before:

After: