Introduce a dedicated parser for prometheus

[DmitrySenin]

closes: #4414

Required for all PRs:

• Signed CLA.
• Associated README.md updated.
• Has appropriate unit tests.

Testing

Tested locally with the following configuration of input:

[[inputs.http_listener_v2]]
  service_address = ":8094"
  path = "/metrics/job/fqt"
  data_format = "prometheus"

[danielnelson]

Since metric_version = 1 is deprecated now, I'd like to keep its use limited to backwards compatibility. Do you think you could split the code so that v1 is only available on the prometheus input and the new parser only does v2?

[DmitrySenin]

@danielnelson , sure. Done

[DmitrySenin]

@danielnelson , Any chance to include it into 1.15? My team is looking forward to this functionality

[danielnelson]

Sorry, we have missed the merge window for 1.15, it will have to go in 1.16.

[platan]

I'm a Telegraf user interested in this feature. I've left some comments, hope it helps you.

[jakemcc]

Just stumbled across this and thought I'd add a comment that we'd also find this useful. Thanks for doing the work.

[jakemcc]

Just checking in on this. Anything missing that I might be able to help with?

[jakemcc]

Not saying this to put any pressure on this being merged but just wanted to report I've been running a build of telegraf with this change and am successfully reporting metrics using it. Thanks for doing the work. 👏 👏 👏

Thanks everyone for putting work in to both manage this project and submit PRs.

[p-zak]

@DmitrySenin it seems that there is conflict with plugins/inputs/prometheus/parser.go

[BlueskyFR]

This should get merged!