Configuring of points per UDP packet

This allows users to configure the number of points stored in a single
UDP packet. This in turn can be used to reduce the number of UDP packets
being sent at the cost of these packets being somewhat larger.

The default setting is 1 point per packet so nothing changes for
existing users.

CHANGELOG

 Please view this file on the master branch, on stable branches it's out of date.
 
 v 8.7.0 (unreleased)
+  - The number of InfluxDB points stored per UDP packet can now be configured
   - Transactions for /internal/allowed now have an "action" tag set
   - Method instrumentation now uses Module#prepend instead of aliasing methods
   - Repository.clean_old_archives is now instrumented

app/controllers/admin/application_settings_controller.rb

@@ -93,6 +93,7 @@ class Admin::ApplicationSettingsController < Admin::ApplicationController
       :akismet_api_key,
       :email_author_in_body,
       :repository_checks_enabled,
+      :metrics_packet_size,
       restricted_visibility_levels: [],
       import_sources: []
     )

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

@@ -218,6 +218,13 @@
         .help-block
           The sampling interval in seconds. Sampled data includes memory usage,
           retained Ruby objects, file descriptors and so on.
+    .form-group
+      = f.label :metrics_packet_size, 'Metrics per packet', class: 'control-label col-sm-2'
+      .col-sm-10
+        = f.number_field :metrics_packet_size, class: 'form-control'
+        .help-block
+          The amount of points to store in a single UDP packet. More points
+          results in fewer but larger UDP packets being sent.
 
   %fieldset
     %legend Spam and Anti-bot Protection

db/migrate/20160419120017_add_metrics_packet_size.rb

+class AddMetricsPacketSize < ActiveRecord::Migration
+  def change
+    add_column :application_settings, :metrics_packet_size, :integer, default: 1
+  end
+end

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20160415133440) do
+ActiveRecord::Schema.define(version: 20160419120017) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -78,6 +78,7 @@ ActiveRecord::Schema.define(version: 20160415133440) do
     t.boolean  "email_author_in_body",              default: false
     t.integer  "default_group_visibility"
     t.boolean  "repository_checks_enabled",         default: true
+    t.integer  "metrics_packet_size",               default: 1
     t.text     "shared_runners_text"
   end
 

lib/gitlab/metrics.rb

@@ -14,7 +14,8 @@ module Gitlab
         method_call_threshold: current_application_settings[:metrics_method_call_threshold],
         host:                  current_application_settings[:metrics_host],
         port:                  current_application_settings[:metrics_port],
-        sample_interval:       current_application_settings[:metrics_sample_interval] || 15
+        sample_interval:       current_application_settings[:metrics_sample_interval] || 15,
+        packet_size:           current_application_settings[:metrics_packet_size] || 1
       }
     end
 
@@ -41,9 +42,9 @@ module Gitlab
       prepared = prepare_metrics(metrics)
 
       pool.with do |connection|
-        prepared.each do |metric|
+        prepared.each_slice(settings[:packet_size]) do |slice|
           begin
-            connection.write_points([metric])
+            connection.write_points(slice)
           rescue StandardError
           end
         end