Tagging metrics

[obmarg]

It would be nice to be able to tag metrics. This isn't something exometer supports (as far as i'm aware), but I could probably simulate it somehow.

Perhaps set up a mapping on the last n parts/pairs of certain metrics to be tags. Might be worth thinking about anyway.

[obmarg]

Another option: we could get clients to store tag info in the Extra parameter of :exometer_report.subscribe...

[obmarg]

Or we could handle exometer.setopts calls in Reporter.exometer_setopts to somehow parse out the tags. Definitely worth doing this I think...

[obmarg]

Ok, so:

• We may need 2 types of options: ones that apply to the whole metric, and ones that apply to each datapoint.
• Whole metric ones:
  • An optional tag to use for the datapoints. This will cause datadog to submit all the datapoints to the same metric, passing the datapoint name in this tag.
• Individual metric ones:
  • The destination metric name.
  • Any additional tags.

We could pull these tags from the Extra parameter of the subscription by default, but also support taking them from setopts. Might be good to look at what the API for setting this stuff up would look like.

Would also be good to add "global" tags - for things like application_name, etc.

[obmarg]

Another potential requirement (maybe one for implemeting later) would be to allow "generic" config. Something along the lines of being able to give a metric pattern, and have any matching metric inherit that config somehow.

e.g. We might want response times from some endpoints to go into the same metric with different tags:

request.time.endpoint1.mean
request.time.endpoint2.mean

Would be nice to not have to manually configure each metric...