Add priority queue to notifications

Significant delays are happening in high priority messages being
delivered to clients due to lack of delivery prioritization. Implement
simple delivery prioritization with "high priority" queue to prevent
password resets and other high priority messages from being delayed.

Test plan:
* Deploy to canary or beta environment
* Create user with @instructure.com email address
* Take user through password reset process and confirm that email is
  received

refs SAS-1442

Change-Id: I0b4f98ac03c5a5ee24e903a913614c005a12ead8
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/231036
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Reviewed-by: Rob Orton <rob@instructure.com>
Reviewed-by: Cody Cutrer <cody@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Jonathan Featherstone <jfeatherstone@instructure.com>

app/models/message.rb

@@ -640,7 +640,8 @@ class Message < ActiveRecord::Base
           notification_service_id,
           notification_message,
           path_type,
-          target
+          target,
+          self.notification.priority?
         )
       end
       complete_dispatch

lib/services/notification_service.rb

@@ -1,5 +1,5 @@
 #
-# Copyright (C) 2016 - present Instructure, Inc.
+# Copyright (C) 2020 - present Instructure, Inc.
 #
 # This file is part of Canvas.
 #
@@ -20,34 +20,50 @@ require 'aws-sdk-sqs'
 
 module Services
   class NotificationService
-    def self.process(global_id, body, type, to)
-      return unless notification_queue.present?
+    def self.process(global_id, body, type, to, priority=false)
+      queue_url = choose_queue_url(priority)
+      return unless queue_url.present?
 
-      notification_queue.send_message(message_body: {
+      notification_sqs.send_message(message_body: {
           global_id: global_id,
           type: type,
           message: body,
           target: to,
           request_id: RequestContextGenerator.request_id
         }.to_json,
-        queue_url: @queue_url)
+        queue_url: queue_url)
     end
 
     class << self
       private
 
-      def notification_queue
+      QUEUE_NAME_KEYS = {
+        priority: 'notification_service_priority_queue_name',
+        default: 'notification_service_queue_name'
+      }.freeze
+
+      def notification_sqs
         return nil if config.blank?
 
-        @notification_queue ||= begin
+        @notification_sqs ||= begin
           conf = Canvas::AWS.validate_v2_config(config, 'notification_service.yml')
-          queue_name = conf['notification_service_queue_name']
-          sqs = Aws::SQS::Client.new(conf.except('notification_service_queue_name'))
-          @queue_url = sqs.get_queue_url(queue_name: queue_name).queue_url
+          sqs = Aws::SQS::Client.new(conf.except(*QUEUE_NAME_KEYS.values))
+          @queue_urls = {}
+          QUEUE_NAME_KEYS.each do |key, queue_name_key|
+            queue_name = conf[queue_name_key]
+            next unless queue_name.present?
+            @queue_urls[key] = sqs.get_queue_url(queue_name: queue_name).queue_url
+          end
           sqs
         end
       end
 
+      def choose_queue_url(priority)
+        return nil unless notification_sqs.present?
+        url = @queue_urls[:priority] if priority
+        url || @queue_urls[:default]
+      end
+
       def config
         ConfigFile.load('notification_service') || {}
       end

spec/lib/services/notification_service_spec.rb

@@ -36,7 +36,8 @@ module Services
 
       before(:each) do
         @queue = double('notification queue')
-        allow(NotificationService).to receive(:notification_queue).and_return(@queue)
+        allow(NotificationService).to receive(:notification_sqs).and_return(@queue)
+        allow(NotificationService).to receive(:choose_queue_url).and_return('default')
       end
 
       it "processes email message type" do
@@ -150,7 +151,7 @@ module Services
           }.with_indifferent_access
 
           spy = SendMessageSpy.new
-          allow(NotificationService).to receive(:notification_queue).and_return(spy)
+          allow(NotificationService).to receive(:notification_sqs).and_return(spy)
 
           NotificationService.process(1, 'hello', 'email', 'alice@example.com')
           expect(expected).to eq spy.sent_hash