Change the default adapter from inline to async

activejob/CHANGELOG.md

@@ -1,3 +1,10 @@
+*   Change the default adapter from inline to async. It's a better default as tests will then not mistakenly
+    come to rely on behavior happening synchronously. This is especially important with things like jobs kicked off
+    in Active Record lifecycle callbacks.
+
+    *DHH*
+
+
 ## Rails 5.0.0.beta2 (February 01, 2016) ##
 
 *   No changes.

activejob/lib/active_job/queue_adapter.rb

@@ -10,19 +10,19 @@ module QueueAdapter #:nodoc:
 
     included do
       class_attribute :_queue_adapter, instance_accessor: false, instance_predicate: false
-      self.queue_adapter = :inline
+      self.queue_adapter = :async
     end
 
     # Includes the setter method for changing the active queue adapter.
     module ClassMethods
       # Returns the backend queue provider. The default queue adapter
-      # is the +:inline+ queue. See QueueAdapters for more information.
+      # is the +:async+ queue. See QueueAdapters for more information.
       def queue_adapter
         _queue_adapter
       end
 
       # Specify the backend queue provider. The default queue adapter
-      # is the +:inline+ queue. See QueueAdapters for more
+      # is the +:async+ queue. See QueueAdapters for more
       # information.
       def queue_adapter=(name_or_adapter_or_class)
         self._queue_adapter = interpret_adapter(name_or_adapter_or_class)

guides/source/active_job_basics.md

@@ -109,10 +109,12 @@ That's it!
 Job Execution
 -------------
 
-For enqueuing and executing jobs you need to set up a queuing backend, that is to
-say you need to decide for a 3rd-party queuing library that Rails should use.
-Rails itself does not provide a sophisticated queuing system and just executes the
-job immediately if no adapter is set.
+For enqueuing and executing jobs in production you need to set up a queuing backend, 
+that is to say you need to decide for a 3rd-party queuing library that Rails should use.
+Rails itself only provides an in-process queuing system, which only keeps the jobs in RAM.
+If the process crashes or the machine is reset, then all outstanding jobs are lost with the
+default async back-end. This may be fine for smaller apps or non-critical jobs, but most
+production apps will need to pick a persistent backend.
 
 ### Backends