Port 'Add uuid to usage ping' to CE

CE port of https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/1521

db/migrate/20170328010804_add_uuid_to_application_settings.rb

+class AddUuidToApplicationSettings < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def up
+    add_column :application_settings, :uuid, :string
+    execute("UPDATE application_settings SET uuid = #{quote(SecureRandom.uuid)}")
+  end
+
+  def down
+    remove_column :application_settings, :uuid
+  end
+end

db/schema.rb

@@ -117,6 +117,7 @@ ActiveRecord::Schema.define(version: 20170408033905) do
     t.boolean "unique_ips_limit_enabled", default: false, null: false
     t.decimal "polling_interval_multiplier", default: 1.0, null: false
     t.boolean "usage_ping_enabled", default: true, null: false
+    t.string "uuid"
   end
   create_table "audit_events", force: :cascade do |t|

lib/gitlab/usage_data.rb

 module Gitlab
   class UsageData
+    include Gitlab::CurrentSettings
+
     class << self
       def data
         Rails.cache.fetch('usage_data', expires_in: 1.hour) { uncached_data }
@@ -45,7 +47,8 @@ module Gitlab
       end
       def license_usage_data
-        usage_data = { version: Gitlab::VERSION,
+        usage_data = { uuid: current_application_settings.uuid,
+                       version: Gitlab::VERSION,
                        active_user_count: User.active.count,
                        recorded_at: Time.now,
                        mattermost_enabled: Gitlab.config.mattermost.enabled }

spec/lib/gitlab/usage_data_spec.rb

@@ -12,9 +12,10 @@ describe Gitlab::UsageData do
       expect(subject.keys).to match_array(%i(
         active_user_count
         counts
-        version
         recorded_at
         mattermost_enabled
+        version
+        uuid
       ))
     end
@@ -57,6 +58,7 @@ describe Gitlab::UsageData do
     subject { Gitlab::UsageData.license_usage_data }
     it "gathers license data" do
+      expect(subject[:uuid]).to eq(current_application_settings.uuid)
       expect(subject[:version]).to eq(Gitlab::VERSION)
       expect(subject[:active_user_count]).to eq(User.active.count)
       expect(subject[:recorded_at]).to be_a(Time)