Changed reentrant -> idempotent

FAQ

@@ -635,7 +635,7 @@ use manual acknowledgement)
 In addition `Task.retry` has features not available in AMQP
 transactions: delay between retries, max retries, etc.
 
-So use retry for Python errors, and if your task is reentrant
+So use retry for Python errors, and if your task is idempotent
 combine that with `acks_late` if that level of reliability
 is required.
 

docs/userguide/optimizing.rst

@@ -108,10 +108,10 @@ are child processes.
 
 But this is not possible without enabling late acknowledgements
 acknowledgements; A task that has been started, will be
-retried if the worker crashes mid execution so the task must be `reentrant`_
+retried if the worker crashes mid execution so the task must be `idempotent`_
 (see also notes at :ref:`faq-acks_late-vs-retry`).
 
-.. _`reentrant`: http://en.wikipedia.org/wiki/Reentrant_(subroutine)
+.. _`idempotent`: http://en.wikipedia.org/wiki/Idempotent
 
 You can enable this behavior by using the following configuration options: