Init http_request_duration_seconds metric

config/initializers/7_prometheus_metrics.rb

@@ -30,6 +30,8 @@ Gitlab::Application.configure do |config|
   config.middleware.insert(1, Gitlab::Metrics::RequestsRackMiddleware)
 end
 
+Gitlab::Metrics::RequestsRackMiddleware.initialize_http_request_duration_seconds
+
 Sidekiq.configure_server do |config|
   config.on(:startup) do
     # webserver metrics are cleaned up in config.ru: `warmup` block

lib/gitlab/metrics/requests_rack_middleware.rb

@@ -3,6 +3,9 @@
 module Gitlab
   module Metrics
     class RequestsRackMiddleware
+      METHODS = %w(delete get head options patch post put trace).freeze
+      STATUSES = %w(200 301 304 400 401 403 404 500).freeze
+
       def initialize(app)
         @app = app
       end
@@ -20,6 +23,14 @@ module Gitlab
                                                            {}, [0.05, 0.1, 0.25, 0.5, 0.7, 1, 2.5, 5, 10, 25])
       end
 
+      def self.initialize_http_request_duration_seconds
+        METHODS.each do |method|
+          STATUSES.each do |status|
+            ::Gitlab::Metrics.histogram(:http_request_duration_seconds, 'Request handling execution time').get({ method: method, status: status })
+          end
+        end
+      end
+
       def call(env)
         method = env['REQUEST_METHOD'].downcase
         started = Time.now.to_f