Merge branch 'adam-build-missing-services-when-necessary' into 'master'

Defer saving project services to the database if there are no user changes

## What does this MR do?

It defers saving project services to the database as long as it is possible. It creates a project service when creating a project only if this project service has an active template. After that project services are saved on the first edit.

## Are there points in the code the reviewer needs to double check?

- tests that used `build_missing_services` before the change
- number of queries executed

## Why was this MR needed?

Motivation in #22281

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing
- [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?

Fixes #22281

See merge request !6958

2 files changed, 14 insertions, 10 deletions

diff --git a/app/models/project.rb b/app/models/project.rb
index 327f81412f8..4aedc91dc34 100644
--- a/app/models/project.rb
+++ b/app/models/project.rb
@@ -77,7 +77,6 @@ class Project < ActiveRecord::Base
   has_many :boards, before_add: :validate_board_limit, dependent: :destroy
 
   # Project services
-  has_many :services
   has_one :campfire_service, dependent: :destroy
   has_one :drone_ci_service, dependent: :destroy
   has_one :emails_on_push_service, dependent: :destroy
@@ -749,27 +748,32 @@ class Project < ActiveRecord::Base
     update_column(:has_external_wiki, services.external_wikis.any?)
   end
 
-  def build_missing_services
+  def find_or_initialize_services
     services_templates = Service.where(template: true)
 
-    Service.available_services_names.each do |service_name|
+    Service.available_services_names.map do |service_name|
       service = find_service(services, service_name)
 
-      # If service is available but missing in db
-      if service.nil?
+      if service
+        service
+      else
         # We should check if template for the service exists
         template = find_service(services_templates, service_name)
 
         if template.nil?
-          # If no template, we should create an instance. Ex `create_gitlab_ci_service`
-          public_send("create_#{service_name}_service")
+          # If no template, we should create an instance. Ex `build_gitlab_ci_service`
+          public_send("build_#{service_name}_service")
         else
-          Service.create_from_template(self.id, template)
+          Service.build_from_template(id, template)
         end
       end
     end
   end
 
+  def find_or_initialize_service(name)
+    find_or_initialize_services.find { |service| service.to_param == name }
+  end
+
   def create_labels
     Label.templates.each do |label|
       params = label.attributes.except('id', 'template', 'created_at', 'updated_at')
diff --git a/app/models/service.rb b/app/models/service.rb
index 625fbc48302..9d6ff190cdf 100644
--- a/app/models/service.rb
+++ b/app/models/service.rb
@@ -222,11 +222,11 @@ class Service < ActiveRecord::Base
     ]
   end
 
-  def self.create_from_template(project_id, template)
+  def self.build_from_template(project_id, template)
     service = template.dup
     service.template = false
     service.project_id = project_id
-    service if service.save
+    service
   end
 
   private