Cache bunny connection

app/models/application_record.rb

@@ -1,6 +1,7 @@
 class ApplicationRecord < ActiveRecord::Base
   self.abstract_class = true
-  after_save :maybe_broadcast, on: [:create, :update, :destroy]
+  after_save    :maybe_broadcast, on: [:create, :update]
+  after_destroy :maybe_broadcast
 
   DONT_BROADCAST = [ "current_sign_in_at",
                      "last_sign_in_at",
@@ -8,17 +9,22 @@ class ApplicationRecord < ActiveRecord::Base
                      "updated_at",
                      "created_at" ]
 
-  def broadcast?
-    Device.current &&
-      !self.saved_changes.except(*self.class::DONT_BROADCAST).empty?
+  # Determine if the changes to the model are worth broadcasting or not.
+  # Reduces network noise.
+  def notable_changes?
+    !self.saved_changes.except(*self.class::DONT_BROADCAST).empty?
   end
 
-  def maybe_broadcast(*args_)
+  def broadcast?
+    Device.current && (destroyed? || notable_changes?)
+  end
+
+  def maybe_broadcast
     self.broadcast! if broadcast?
   end
 
   def broadcast_payload
-    { body: self.as_json }.to_json
+    { body: destroyed? ? "null" : self.as_json }.to_json
   end
 
   def chan_name

app/models/transport.rb

@@ -1,12 +1,15 @@
 # A wrapper around AMQP to stay DRY. Will make life easier if we ever need to
 # change protocols
 module Transport
+  def self.topic
+    @topic ||= Bunny
+                 .new(read_timeout: 10, heartbeat: 10)
+                 .start
+                 .create_channel
+                 .topic("amq.topic", auto_delete: true)
+  end
+
   def self.send(message, id, channel)
-    Bunny
-      .new
-      .start
-      .create_channel
-      .topic("amq.topic", auto_delete: true)
-      .publish(message, routing_key: "bot.device_#{id}.#{channel}")
+      topic.publish(message, routing_key: "bot.device_#{id}.#{channel}")
   end
 end