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:

[tbauriedel]

To solve the problem mentioned above, deep changes to the module are necessary, which would significantly change the behaviour.
In order to provide clear compatibility with all versions, support for the different API versions must be built.
Due to the depth and complexity of the module at this point, these changes currently exceed my possible time frame, which is why I am dependent on the support of Icinga.

If you (Icinga) are interested in supporting the current stack around Graphite, I would be happy to provide further information on which steps would need to be adapted from the Graphite / CarbonApi perspective.