services: gunicorn: Allow configuration of control-socket.

Since gunicorn is run in its own Linux namespace, where $HOME is
read-only, creating that control-socket fails and prevents gunicorn
from starting by default.  Therefore, this patch disables it by
default but allows supplying a custom path via a newly added
configuration field.

* gnu/services/web.scm (gunicorn-app): Add gunicorn-app-control-socket.
(gunicorn-shepherd-services): Respect gunicorn-app-control-socket.
* doc/guix.texi (gunicorn-app): Document it.

Change-Id: I648079b630293a47801713425728a4d602c8088c

1 files changed, 4 insertions, 0 deletions

diff --git a/doc/guix.texi b/doc/guix.texi
index b4eebc8e145..f91e8cee845 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -36277,6 +36277,10 @@ Launch the app as this group (it must be an existing group).
 A list of sockets (as path strings) which gunicorn will be listening
 on.  This list must contain at least one socket.
 
+@item @code{control-socket} (default: #f) (type: string)
+If set, creates a gunicorn control-socket at the given path.  Note that,
+the control socket should refer to a path listed in @code{mappings}.
+
 @item @code{socket-user} (default: @code{user}) (type: string)
 Owner of the directory containing the socket (must be an existing user).