[6.0] 296b3ebc4 Add Backend None Documentation

[Dridi Boukelmoune]

commit 296b3ebc41ffa094e1a4d9e5fc9d64a422d4ec11
Author: Andrew Wiik <andrew at varnish-software.com>
Date:   Mon Oct 7 20:28:19 2019 -0400

    Add Backend None Documentation

diff --git a/doc/sphinx/reference/vcl.rst b/doc/sphinx/reference/vcl.rst
index 4057ee50a..7b3768853 100644
--- a/doc/sphinx/reference/vcl.rst
+++ b/doc/sphinx/reference/vcl.rst
@@ -286,6 +286,12 @@ parameters. The following attributes are available:
     Varnish reaches the maximum Varnish it will start failing
     connections.
 
+Empty backends can also be defined using the following syntax.::
+
+  backend name none;
+
+An empty backend will always return status code 503 as if it is sick.
+
 Backends can be used with *directors*. Please see the
 :ref:`vmod_directors(3)` man page for more information.
 
diff --git a/doc/sphinx/users-guide/vcl-backends.rst b/doc/sphinx/users-guide/vcl-backends.rst
index 58448916f..f4c8d37eb 100644
--- a/doc/sphinx/users-guide/vcl-backends.rst
+++ b/doc/sphinx/users-guide/vcl-backends.rst
@@ -31,6 +31,9 @@ Varnish can have several backends defined you can even join
 several backends together into clusters of backends for load balancing
 purposes.
 
+backends can also be empty or 'none' with the following syntax.::
+
+    backend default none;
 
 Multiple backends
 -----------------