Merge branch '5.2' into 5.x

* 5.2:
  [Messenger] More on unique Redis consumer names

Author: javiereguiluz

messenger.rst

@@ -649,8 +649,18 @@ times:
     process_name=%(program_name)s_%(process_num)02d
 
 Change the ``async`` argument to use the name of your transport (or transports)
-and ``user`` to the Unix user on your server. Next, tell Supervisor to read your
-config and start your workers:
+and ``user`` to the Unix user on your server.
+
+If you use the Redis Transport, note that each worker needs a unique consumer
+name to avoid the same message being handled by multiple workers. One way to
+achieve this is to set an environment variable in the Supervisor configuration
+file, which you can then refer to in ``messenger.yaml`` (see Redis section above):
+
+.. code-block:: ini
+
+    environment=MESSENGER_CONSUMER_NAME=%(program_name)s_%(process_num)02d
+
+Next, tell Supervisor to read your config and start your workers:
 
 .. code-block:: terminal
 
@@ -1380,9 +1390,13 @@ claim_interval       Interval on which pending/abandoned    ``60000`` (1 Minute)
 .. caution::
 
     There should never be more than one ``messenger:consume`` command running with the same
-    config (stream, group and consumer name) to avoid having a message handled more than once.
-    Using the ``HOSTNAME`` as the consumer might often be a good idea. In case you are using
-    Kubernetes to orchestrate your containers, consider using a ``StatefulSet``.
+    combination of ``stream``, ``group`` and ``consumer``, or messages could end up being
+    handled more than once. If you run multiple queue workers, ``consumer`` can be set to an
+    environment variable (like ``%env(MESSENGER_CONSUMER_NAME)%``) set by Supervisor
+    (example below) or any other service used to manage the worker processes.
+    In a container environment, the ``HOSTNAME`` can be used as the consumer name, since
+    there is only one worker per container/host. If using Kubernetes to orchestrate the
+    containers, consider using a ``StatefulSet`` to have stable names.
 
 .. tip::