Contents

# frozen_string_literal: true

require "prometheus_aggregator"

module PrometheusAggregator
  class RackMiddleware
    def initialize(app, options = {})
      @app = app
      @client = options[:client]
      raise ArgumentError, ":client option is required" unless @client
    end

    def call(env)
      start_time = Time.now
      response = @app.call(env)
      duration = Time.now - start_time

      begin
        @client.counter(
          name: "http_server_requests_total",
          help: "The total number of HTTP requests handled by the Rack app",
          value: 1,
          labels: labels(env).merge(code: response.first.to_s)
        )

        @client.histogram(
          name: "http_server_request_duration_seconds",
          help: "The HTTP response duration of the Rack application",
          value: duration,
          labels: labels(env)
        )
      rescue => err # rubocop:disable Style/RescueStandardError
        # Let's be ultra defensive. Metrics should never break the app.
        PrometheusAggregator.logger.error("RackMiddleware: #{err}")
      end

      response
    end

    def labels(env)
      {
        method: env["REQUEST_METHOD"].downcase,
        path: clean_path(env["PATH_INFO"])
      }
    end

    def clean_path(path)
      path.gsub(%r{/\d+/}, "/:id/").gsub(%r{/\d+$}, "/:id")
    end
  end
end

Version data entries

4 entries across 4 versions & 1 rubygems

Version	Path
prometheus_aggregator-1.0.0	lib/prometheus_aggregator/rack_middleware.rb
prometheus_aggregator-0.2.0	lib/prometheus_aggregator/rack_middleware.rb
prometheus_aggregator-0.1.1	lib/prometheus_aggregator/rack_middleware.rb
prometheus_aggregator-0.1.0	lib/prometheus_aggregator/rack_middleware.rb