Exometer NewRelic Reporter

This uses exometer for metrics gathering and is installed with Pinterest's elixometer wrapper which makes tracking timings and generating Exometer stats really simple and easy.

Metrics are, of course, reported to New Relic. The code pretends to be a New Relic python agent and so you may notice that it shows up as Python in New Relic because New Relic does not yet support Erlang or Elixir.

Installation

1. Add exometer_newrelic_reporter to your list of dependencies in mix.exs:

def deps do
  [ {:exometer_newrelic_reporter, github: "nitro/exometer_newrelic_reporter"} ]
end

2. Ensure exometer_newrelic_reporter is started before your application and before elixometer:

   def application do
     [applications: [:exometer_newrelic_reporter, :elixometer]]
   end

Configuration

The following assumes you're using Elixometer though configuration should be similar for Exometer:

# If we have a NEW_RELIC_LICENSE_KEY, we'll use a New Relic reporter
if System.get_env("NEW_RELIC_LICENSE_KEY") != "" do
  config :exometer_core, report: [
    reporters: ["Elixir.Exometer.NewrelicReporter":
      [
        application_name: "Spacesuit #{Mix.env}",
        license_key: System.get_env("NEW_RELIC_LICENSE_KEY"),
        synthesize_metrics: %{
          "proxyHandler-handle" => "HttpDispatcher"
        }
      ]
    ]
  ]

  config :elixometer, reporter: :"Elixir.Exometer.NewrelicReporter",
    update_frequency: 60_000
end

Note the "Elixir." prefix when setting our module, this is required by exometer and Erlang in order to lookup the module.

Note you must set the update_frequency to 60,000 which is the expected timeframe (60 seconds) for a New Relic agent. Anything else will lead to unhappiness.

Synthesized Metrics vs Raw Metrics

By default anything captured by an Elixometer @timed annotation will be sent as histogram metrics suitable for display on a custom dashboard at New Relic. Fields will all be sent as "Call count" values. These we're calling Raw Metrics.

But New Relic metrics actually contain a few fields that allow them to be used in the normal ways you expect. They actually contain:

[call_count, total, exclusive, min, max, sum_of_squares]

This reporter supports generating metrics that look like this from histograms used by Exometer's timed traces. You'll probably want to simulate an HttpDispatcher metric, for example, to capture the normal response time and throughput for your application. In the example configuration above, you see a section labeled synthesize_metrics. This is taking a metrics we've called proxyHandler-handle internally and turning it into a HttpDispatcher metric so that we can see the two main charts on the New Relic application page.

The annotation we used in our application to grab that proxyHandler-handle metric looks like this:

  @timed(key: "timed.proxyHandler-handle", units: :millisecond)
  def handle(...) do
	# The thing you want to time
  end

Note: The units entry is important here. Elixometer will by default capture in microseconds, which is not what New Relic is expecting. If you don't pass this value, you'll see weird numbers in the New Relic console.