Verified Commit e042d2af authored by Hercules Merscher's avatar Hercules Merscher 🌴
Browse files

feat: Retrieving a metric by the name 

The method Labkit::Metrics::Client.get returns a predefined metric,
be it a counter, gauge, summary, or histogram. Or returns nil if it
does not exist.
parent b69acbdb

lib/labkit/metrics/README.md

+5 −2
Original line number Diff line number Diff line
@@ -3,13 +3,16 @@ 
## Usage



```ruby

# create a new counter metric

# create a new counter metric and returns it

http_requests = Labkit::Metrics::Client.counter(:http_requests, 'A counter of HTTP requests made')

# start using the counter

http_requests.increment



# resets the registry and reinitializes all metrics files.

# resets the registry and reinitializes all metrics files

Labkit::Metrics::Client.reset!



# retrieves the metric (be it a counter, gauge, histogram, summary)

http_requests = Labkit::Metrics::Client.get(:http_requests)

```



### Counter

lib/labkit/metrics/client.rb

+5 −1
Original line number Diff line number Diff line
@@ -72,12 +72,16 @@ module Labkit 
        Registry.reset!

      end



      def get(metric_name)

        Registry.get(metric_name)

      end



      class << self

        extend Forwardable



        def_delegators :instance,

          :enable!, :disable!, :counter, :gauge, :histogram, :summary, :reset!, :enabled?,

          :configure, :reinitialize_on_pid_change, :configuration

          :configure, :reinitialize_on_pid_change, :configuration, :get



        private :instance

      end

lib/labkit/metrics/registry.rb

+9 −1
Original line number Diff line number Diff line
@@ -30,7 +30,7 @@ module Labkit 
        #   counter = Registry.safe_register(:counter, :http_requests_total, 'Total HTTP requests')

        def safe_register(metric_type, name, *args)

          REGISTER_MUTEX.synchronize do

            wrapped_registry.get(name) || wrapped_registry.method(metric_type).call(name, *args)

            get(name) || wrapped_registry.method(metric_type).call(name, *args)

          end

        end
@@ -43,6 +43,14 @@ module Labkit 
          end

        end



        # Returns the metric for the given name from the Prometheus registry.

        #

        # @param metric_name [Symbol, String] The name of the metric

        # @return [Prometheus::Client::Metric, nil] The registered metric or nil if it does not exist

        def get(metric_name)

          wrapped_registry.get(metric_name)

        end



        private



        def wrapped_registry

spec/labkit/metrics/client_spec.rb

+16 −7
Original line number Diff line number Diff line
@@ -3,13 +3,6 @@ 
require "prometheus/client"



RSpec.describe Labkit::Metrics::Client, :with_metrics_config do

  [

    [:counter, Prometheus::Client::Counter],

    [:histogram, Prometheus::Client::Histogram],

    [:summary, Prometheus::Client::Summary],

    [:gauge, Prometheus::Client::Gauge]

  ].each do |(metric_type, metric_class)|

    describe ".#{metric_type}" do

  let(:info) do

    {

      name: :metric_example,
@@ -18,6 +11,13 @@ RSpec.describe Labkit::Metrics::Client, :with_metrics_config do 
    }

  end



  [

    [:counter, Prometheus::Client::Counter],

    [:histogram, Prometheus::Client::Histogram],

    [:summary, Prometheus::Client::Summary],

    [:gauge, Prometheus::Client::Gauge]

  ].each do |(metric_type, metric_class)|

    describe ".#{metric_type}" do

      subject(:metric) { described_class.send(metric_type, info[:name], info[:docstring], info[:base_labels]) }



      it "registers a #{metric_type}" do
@@ -37,6 +37,15 @@ RSpec.describe Labkit::Metrics::Client, :with_metrics_config do 
        expect(metric).to be_a Labkit::Metrics::Null

      end

    end



    describe ".get" do

      it "returns registered #{metric_type}" do

        metric = described_class.send(metric_type, info[:name], info[:docstring], info[:base_labels])

        previously_registered_metric = described_class.get(info[:name])



        expect(previously_registered_metric).to eq metric

      end

    end

  end



  describe '.reset!' do

spec/labkit/metrics/registry_spec.rb

+9 −0
Original line number Diff line number Diff line
@@ -21,5 +21,14 @@ RSpec.describe Labkit::Metrics::Registry, :with_metrics_config do 
        expect(metric2).to eq metric

      end

    end



    describe "#get" do

      it "returns registered #{metric_type}" do

        metric = described_class.safe_register(metric_type, metric_name, docstring, base_labels)

        previously_registered_metric = described_class.get(metric_name)



        expect(previously_registered_metric).to eq metric

      end

    end

  end

end