Merge branch 'separate-sidekiq-queues' into 'master'

Use separate queues for all Sidekiq workers

## What does this MR do?

This MR updates all workers so that they (mostly) use their own Sidekiq queues. This in turn allows us to monitor queues more accurately and in the future impose queue specific throttles, limits, etc.

This is a critical part we need in 8.13, despite it being so close to release day.

See https://gitlab.com/gitlab-org/gitlab-ce/issues/23370 for more information.

## 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)
- [x] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ce/issues/23370

See merge request !7006

2 files changed, 48 insertions, 1 deletions

diff --git a/config/application.rb b/config/application.rb
index f3337b00dc6..92c8467e7f4 100644
--- a/config/application.rb
+++ b/config/application.rb
@@ -24,7 +24,8 @@ module Gitlab
                                      #{config.root}/app/models/ci
                                      #{config.root}/app/models/hooks
                                      #{config.root}/app/models/members
-                                     #{config.root}/app/models/project_services))
+                                     #{config.root}/app/models/project_services
+                                     #{config.root}/app/workers/concerns))
 
     config.generators.templates.push("#{config.root}/generator_templates")
 
diff --git a/config/sidekiq_queues.yml b/config/sidekiq_queues.yml
new file mode 100644
index 00000000000..c2e880e891f
--- /dev/null
+++ b/config/sidekiq_queues.yml
@@ -0,0 +1,46 @@
+# This configuration file should be exclusively used to set queue settings for
+# Sidekiq. Any other setting should be specified using the Sidekiq CLI or the
+# Sidekiq Ruby API (see config/initializers/sidekiq.rb).
+---
+# All the queues to process and their weights. Every queue _must_ have a weight
+# defined.
+#
+# The available weights are as follows
+#
+# 1: low priority
+# 2: medium priority
+# 3: high priority
+# 5: _super_ high priority, this should only be used for _very_ important queues
+#
+# As per http://stackoverflow.com/a/21241357/290102 the formula for calculating
+# the likelihood of a job being popped off a queue (given all queues have work
+# to perform) is:
+#
+#     chance = (queue weight / total weight of all queues) * 100
+:queues:
+  - [post_receive, 5]
+  - [merge, 5]
+  - [update_merge_requests, 3]
+  - [new_note, 2]
+  - [build, 2]
+  - [pipeline, 2]
+  - [gitlab_shell, 2]
+  - [email_receiver, 2]
+  - [emails_on_push, 2]
+  - [repository_fork, 1]
+  - [repository_import, 1]
+  - [project_service, 1]
+  - [clear_database_cache, 1]
+  - [delete_user, 1]
+  - [expire_build_instance_artifacts, 1]
+  - [group_destroy, 1]
+  - [irker, 1]
+  - [project_cache, 1]
+  - [project_destroy, 1]
+  - [project_export, 1]
+  - [project_web_hook, 1]
+  - [repository_check, 1]
+  - [system_hook, 1]
+  - [git_garbage_collect, 1]
+  - [cronjob, 1]
+  - [default, 1]