[Fix #190] Add httpjson tags support

[palkan]

Tags are extracted from JSON response according to the list of tags in config.

Example:

# config
[httpjson.services]
  tagKeys = [
    "role",
    "build"
  ]

# server response
{
  "value": 123,
  "role": "master",
  "build": "2015"
}

And resulting point will contain values value: 123 and tags role: master build: 2015 server_name: ....

[sparrc]

awesome, thank you @palkan! I see that you have another PR to fix the test issue too :-)

Could you also write a short README for this plugin, and include the info you wrote above about tagging? You can use the exec plugin as an example.

[sparrc]

also, just to clarify, do these tag keys need to be in the top-level of the map?

[sparrc]

indentation, should all be tabs in Go

[sparrc]

I like this, and I also opened #277 to allow for a more general tags key to be used to add ad-hoc tags.

[sparrc]

@palkan one more thing: can you change the name tags to tagkeys so that it's more clear that we are referring to keys from the JSON that will be used as tags

[sparrc]

comment this by default

[palkan]

Tags should be in the top level of the map. Of course, we can look for tags in lower levels, but we have to consider prefixes here. One possible solution is to flatten JSON first, and provide tags names with prefixes, e.g.:

# json
{
  "key": 1,
  "some": {
    "key": 2
  },
  "none": {
     "key": 3
   },
}

and config

[httpjson]
  tagKeys = [
    "key",
    "some_key"
  ]

will produce httpjson_service,key=1,some_key=2 ....

[palkan]

@sparrc
We're waiting until we end up with something in #277?

[sparrc]

sorry for the delay @palkan, I'll get this merged this weekend 👍