add propagate service worker and updated spec and controller

app/controllers/admin/services_controller.rb

@@ -15,7 +15,7 @@ class Admin::ServicesController < Admin::ApplicationController
   end
   def update
-    if service.update_attributes(service_params[:service])
+    if service.update_and_propagate(service_params[:service])
       redirect_to admin_application_settings_services_path,
         notice: 'Application settings saved successfully'
     else

app/models/service.rb

@@ -254,6 +254,16 @@ class Service < ActiveRecord::Base
     service
   end
+  def update_and_propagate(service_params)
+    return false unless update_attributes(service_params)
+
+    if service_params[:active] == 1
+      PropagateProjectServiceWorker.perform_async(service_params[:id])
+    end
+
+    true
+  end
+
   private
   def cache_project_has_external_issue_tracker

app/workers/propagate_project_service_worker.rb

+# Worker for updating any project specific caches.
+class PropagateProjectServiceWorker
+  include Sidekiq::Worker
+  include DedicatedSidekiqQueue
+
+  LEASE_TIMEOUT = 30.minutes.to_i
+
+  def perform(template_id)
+    template = Service.find_by(id: template_id)
+
+    return unless template&.active
+    return unless try_obtain_lease_for(template.id)
+
+    Rails.logger.info("Propagating services for template #{template.id}")
+
+    project_ids_for_template(template) do |project_id|
+      Service.build_from_template(project_id, template).save!
+    end
+  end
+
+  private
+
+  def project_ids_for_template(template)
+    limit = 100
+    offset = 0
+
+    loop do
+      batch = project_ids_batch(limit, offset, template.type)
+
+      batch.each { |project_id| yield(project_id) }
+
+      break if batch.count < limit
+
+      offset += limit
+    end
+  end
+
+  def project_ids_batch(limit, offset, template_type)
+    Project.joins('LEFT JOIN services ON services.project_id = projects.id').
+      where('services.type != ? OR services.id IS NULL', template_type).
+      limit(limit).offset(offset).pluck(:id)
+  end
+
+  def try_obtain_lease_for(template_id)
+    Gitlab::ExclusiveLease.
+      new("propagate_project_service_worker:#{template_id}", timeout: LEASE_TIMEOUT).
+      try_obtain
+  end
+end

spec/workers/propagate_project_service_worker_spec.rb

 require 'spec_helper'
-describe PruneOldEventsWorker do
+describe PropagateProjectServiceWorker do
   describe '#perform' do
     let!(:service_template) do
       PushoverService.create(
         template: true,
+        active: true,
         properties: {
           device: 'MyDevice',
           sound: 'mic',
           priority: 4,
+          user_key: 'asdf',
           api_key: '123456789'
         })
     end
     let!(:project) { create(:empty_project) }
+    before do
+      allow_any_instance_of(Gitlab::ExclusiveLease).to receive(:try_obtain).
+        and_return(true)
+    end
+
     it 'creates services for projects' do
-      expect { subject.perform }.to change { Service.count }.by(1)
+      expect { subject.perform(service_template.id) }.to change { Service.count }.by(1)
     end
     it 'does not create the service if it exists already' do
       Service.build_from_template(project.id, service_template).save!
-      expect { subject.perform }.not_to change { Service.count }
+      expect { subject.perform(service_template.id) }.not_to change { Service.count }
     end
     it 'creates the service containing the template attributes' do
-      subject.perform
-      service = Service.find_by(service_template.merge(project_id: project.id, template: false))
-      expect(service).not_to be_nil
+      subject.perform(service_template.id)
+      service = Service.find_by(type: service_template.type, template: false)
+      expect(service.properties).to eq(service_template.properties)
     end
   end
 end