Move prometheus middle ware to prometheus initialized.

Gemfile

@@ -283,7 +283,7 @@ group :metrics do
   gem 'influxdb', '~> 0.2', require: false
   # Prometheus
-  gem 'prometheus-client-mmap', '~> 0.7.0.beta33'
+  gem 'prometheus-client-mmap', '~> 0.7.0.beta36'
   gem 'raindrops', '~> 0.18'
 end

Gemfile.lock

@@ -625,7 +625,7 @@ GEM
       parser
       unparser
     procto (0.0.3)
-    prometheus-client-mmap (0.7.0.beta33)
+    prometheus-client-mmap (0.7.0.beta36)
       mmap2 (~> 2.2, >= 2.2.9)
     pry (0.10.4)
       coderay (~> 1.1.0)
@@ -1111,7 +1111,7 @@ DEPENDENCIES
   peek-sidekiq (~> 1.0.3)
   pg (~> 0.18.2)
   premailer-rails (~> 1.9.7)
-  prometheus-client-mmap (~> 0.7.0.beta33)
+  prometheus-client-mmap (~> 0.7.0.beta36)
   pry-byebug (~> 3.4.1)
   pry-rails (~> 0.3.4)
   rack-attack (~> 4.4.1)

app/views/admin/application_settings/_form.html.haml

@@ -361,6 +361,14 @@
               %code prometheus_multiproc_dir
               does not exist or is not pointing to a valid directory.
               = link_to icon('question-circle'), help_page_path('administration/monitoring/prometheus/gitlab_metrics', anchor: 'metrics-shared-directory')
+    .form-group
+      .col-sm-offset-2.col-sm-10
+        .checkbox
+          = f.label :prometheus_metrics_method_instrumentation_enabled do
+            = f.check_box :prometheus_metrics_method_instrumentation_enabled
+            Track method execution time.
+            .help-block
+              Provides method execution metrics. Can adversely impact GitLab's responsiveness.
   %fieldset
     %legend Profiling - Performance Bar

config/initializers/7_prometheus_metrics.rb

@@ -13,7 +13,6 @@ Prometheus::Client.configure do |config|
   config.pid_provider = -> do
     wid = Prometheus::Client::Support::Unicorn.worker_id
-    wid = Process.pid if wid.nil?
     if wid.nil?
       "process_pid_#{Process.pid}"
     else
@@ -22,6 +21,11 @@ Prometheus::Client.configure do |config|
   end
 end
+Gitlab::Application.configure do |config|
+  # 0 should be Sentry to catch errors in this middleware
+  config.middleware.insert(1, Gitlab::Metrics::RequestsRackMiddleware)
+end
+
 Sidekiq.configure_server do |config|
   config.on(:startup) do
     Gitlab::Metrics::SidekiqMetricsExporter.instance.start

config/initializers/8_metrics.rb

@@ -118,11 +118,6 @@ def instrument_classes(instrumentation)
 end
 # rubocop:enable Metrics/AbcSize
-Gitlab::Application.configure do |config|
-  # 0 should be Sentry to catch errors in this middleware
-  config.middleware.insert(1, Gitlab::Metrics::RequestsRackMiddleware)
-end
-
 if Gitlab::Metrics.enabled?
   require 'pathname'
   require 'influxdb'

db/migrate/20171122211913_add_prometheus_instrumentation_to_application_settings.rb

+class AddPrometheusInstrumentationToApplicationSettings < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+  disable_ddl_transaction!
+
+  def up
+    add_column_with_default(:application_settings, :prometheus_metrics_method_instrumentation_enabled, :boolean,
+                            default: false, allow_null: false)
+  end
+
+  def down
+    remove_column(:application_settings, :prometheus_metrics_method_instrumentation_enabled)
+  end
+end
+

lib/api/settings.rb

@@ -66,6 +66,9 @@ module API
       optional :max_pages_size, type: Integer, desc: 'Maximum size of pages in MB'
       optional :container_registry_token_expire_delay, type: Integer, desc: 'Authorization token duration (minutes)'
       optional :prometheus_metrics_enabled, type: Boolean, desc: 'Enable Prometheus metrics'
+      given prometheus_metrics_enabled: ->(val) { val } do
+        requires :prometheus_metrics_method_instrumentation_enabled, type: Boolean, desc: 'Enable method call instrumentation'
+      end
       optional :metrics_enabled, type: Boolean, desc: 'Enable the InfluxDB metrics'
       given metrics_enabled: ->(val) { val } do
         requires :metrics_host, type: String, desc: 'The InfluxDB host'

lib/gitlab/metrics/method_call.rb

@@ -59,8 +59,10 @@ module Gitlab
         @cpu_time += cpu_time
         @call_count += 1
-        self.class.call_real_duration_histogram.observe(@transaction.labels.merge(labels), real_time / 1000.0)
-        self.class.call_cpu_duration_histogram.observe(@transaction.labels.merge(labels), cpu_time / 1000.0)
+        if prometheus_enabled?
+          self.class.call_real_duration_histogram.observe(@transaction.labels.merge(labels), real_time / 1000.0)
+          self.class.call_cpu_duration_histogram.observe(@transaction.labels.merge(labels), cpu_time / 1000.0)
+        end
         retval
       end
@@ -83,6 +85,10 @@ module Gitlab
       def above_threshold?
         real_time >= Metrics.method_call_threshold
       end
+
+      def prometheus_enabled?
+        @prometheus_enabled ||= current_application_settings(:prometheus_metrics_method_instrumentation_enabled)
+      end
     end
   end
 end