Make the metrics sampler interval configurable

app/controllers/admin/application_settings_controller.rb

@@ -73,6 +73,7 @@ class Admin::ApplicationSettingsController < Admin::ApplicationController
       :metrics_pool_size,
       :metrics_timeout,
       :metrics_method_call_threshold,
+      :metrics_sample_interval,
       :recaptcha_enabled,
       :recaptcha_site_key,
       :recaptcha_private_key,

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

@@ -202,6 +202,13 @@
         .help-block
           A method call is only tracked when it takes longer to complete than
           the given amount of milliseconds.
+    .form-group
+      = f.label :metrics_sample_interval, 'Sampler Interval (sec)', class: 'control-label col-sm-2'
+      .col-sm-10
+        = f.number_field :metrics_sample_interval, class: 'form-control'
+        .help-block
+          The sampling interval in seconds. Sampled data includes memory usage,
+          retained Ruby objects, file descriptors and so on.
   %fieldset
     %legend Spam and Anti-bot Protection

db/migrate/20160113111034_add_metrics_sample_interval.rb

+class AddMetricsSampleInterval < ActiveRecord::Migration
+  def change
+    add_column :application_settings, :metrics_sample_interval, :integer,
+      default: 15
+  end
+end

lib/gitlab/metrics.rb

@@ -13,7 +13,8 @@ module Gitlab
         timeout:               current_application_settings[:metrics_timeout],
         method_call_threshold: current_application_settings[:metrics_method_call_threshold],
         host:                  current_application_settings[:metrics_host],
-        port:                  current_application_settings[:metrics_port]
+        port:                  current_application_settings[:metrics_port],
+        sample_interval:       current_application_settings[:metrics_sample_interval] || 15
       }
     end

lib/gitlab/metrics/sampler.rb

@@ -7,7 +7,7 @@ module Gitlab
     # statistics, etc.
     class Sampler
       # interval - The sampling interval in seconds.
-      def initialize(interval = 15)
+      def initialize(interval = Metrics.settings[:sample_interval])
         @interval = interval
         @metrics  = []