FIX: add a 20 seconds grace period before sending a notification about a PM

app/models/user_email_observer.rb

@@ -29,15 +29,15 @@ class UserEmailObserver < ActiveRecord::Observer
     end
 
     def private_message
-      enqueue_private(:user_private_message, 0)
+      enqueue_private(:user_private_message)
     end
 
     def invited_to_private_message
-      enqueue(:user_invited_to_private_message, 0)
+      enqueue(:user_invited_to_private_message, private_delay)
     end
 
     def invited_to_topic
-      enqueue(:user_invited_to_topic, 0)
+      enqueue(:user_invited_to_topic, private_delay)
     end
 
     def self.notification_params(notification, type)
@@ -64,7 +64,7 @@ class UserEmailObserver < ActiveRecord::Observer
       perform_enqueue(type,delay)
     end
 
-    def enqueue_private(type, delay=default_delay)
+    def enqueue_private(type, delay=private_delay)
       return unless notification.user.email_private_messages?
       perform_enqueue(type,delay)
     end
@@ -76,11 +76,14 @@ class UserEmailObserver < ActiveRecord::Observer
       Jobs.enqueue_in(delay, :user_email, self.class.notification_params(notification, type))
     end
 
-
     def default_delay
       SiteSetting.email_time_window_mins.minutes
     end
 
+    def private_delay
+      20.seconds
+    end
+
   end
 
   def after_commit(notification)

spec/models/user_email_observer_spec.rb

@@ -109,7 +109,7 @@ describe UserEmailObserver do
 
   context 'user_private_message' do
     let(:type) { :user_private_message }
-    let(:delay) { 0 }
+    let(:delay) { 20.seconds }
     let!(:notification) { create_notification(6) }
 
     include_examples "enqueue_private"
@@ -117,7 +117,7 @@ describe UserEmailObserver do
 
   context 'user_invited_to_private_message' do
     let(:type) { :user_invited_to_private_message }
-    let(:delay) { 0 }
+    let(:delay) { 20.seconds }
     let!(:notification) { create_notification(7) }
 
     include_examples "enqueue_public"
@@ -125,7 +125,7 @@ describe UserEmailObserver do
 
   context 'user_invited_to_topic' do
     let(:type) { :user_invited_to_topic }
-    let(:delay) { 0 }
+    let(:delay) { 20.seconds }
     let!(:notification) { create_notification(13) }
 
     include_examples "enqueue_public"