Merge branch 'sidekiq-job-throttling' into 'master'

Allow certain Sidekiq jobs to be throttled

## What does this MR do?

Allows certain slow running Sidekiq jobs to be throttled. It is disabled by default and can be enabled via the Application Settings. 

![Screen_Shot_2016-11-04_at_4.51.24_PM](/uploads/a1f1d24c693fcdb278602765cd404d94/Screen_Shot_2016-11-04_at_4.51.24_PM.png)

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG.md) entry added
- [x] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing

## What are the relevant issue numbers?

Related to #23352

See merge request !7292

2 files changed, 28 insertions, 0 deletions

diff --git a/lib/gitlab/current_settings.rb b/lib/gitlab/current_settings.rb
index ef9160d6437..3a651ef318a 100644
--- a/lib/gitlab/current_settings.rb
+++ b/lib/gitlab/current_settings.rb
@@ -23,6 +23,10 @@ module Gitlab
       settings || fake_application_settings
     end
 
+    def sidekiq_throttling_enabled?
+      current_application_settings.sidekiq_throttling_enabled
+    end
+
     def fake_application_settings
       OpenStruct.new(
         default_projects_limit: Settings.gitlab['default_projects_limit'],
@@ -50,6 +54,7 @@ module Gitlab
         repository_checks_enabled: true,
         container_registry_token_expire_delay: 5,
         user_default_external: false,
+        sidekiq_throttling_enabled: false,
       )
     end
 
diff --git a/lib/gitlab/sidekiq_throttler.rb b/lib/gitlab/sidekiq_throttler.rb
new file mode 100644
index 00000000000..d4d39a888e7
--- /dev/null
+++ b/lib/gitlab/sidekiq_throttler.rb
@@ -0,0 +1,23 @@
+module Gitlab
+  class SidekiqThrottler
+    class << self
+      def execute!
+        if Gitlab::CurrentSettings.sidekiq_throttling_enabled?
+          Gitlab::CurrentSettings.current_application_settings.sidekiq_throttling_queues.each do |queue|
+            Sidekiq::Queue[queue].limit = queue_limit
+          end
+        end
+      end
+
+      private
+
+      def queue_limit
+        @queue_limit ||=
+          begin
+            factor = Gitlab::CurrentSettings.current_application_settings.sidekiq_throttling_factor
+            (factor * Sidekiq.options[:concurrency]).ceil
+          end
+      end
+    end
+  end
+end