docs: complement uwsgi documentation for all distros

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

2 files changed, 93 insertions, 0 deletions

diff --git a/docs/admin/installation-searx.rst b/docs/admin/installation-searx.rst
index 76449beb6..88562f3e3 100644
--- a/docs/admin/installation-searx.rst
+++ b/docs/admin/installation-searx.rst
@@ -12,6 +12,8 @@ Step by step installation
 Step by step installation with virtualenv.  For Ubuntu, be sure to have enable
 universe repository.
 
+.. _install packages:
+
 Install packages
 ================
 
diff --git a/docs/admin/installation-uwsgi.rst b/docs/admin/installation-uwsgi.rst
index f9161679f..7996bf937 100644
--- a/docs/admin/installation-uwsgi.rst
+++ b/docs/admin/installation-uwsgi.rst
@@ -4,6 +4,97 @@
 uwsgi
 =====
 
+.. sidebar:: further read
+
+   - `systemd.unit`_
+   - `uWSGI Emperor`_
+
+.. contents:: Contents
+   :depth: 2
+   :local:
+   :backlinks: entry
+
+
+.. _systemd.unit: https://www.freedesktop.org/software/systemd/man/systemd.unit.html
+.. _One service per app in systemd:
+    https://uwsgi-docs.readthedocs.io/en/latest/Systemd.html#one-service-per-app-in-systemd
+.. _uWSGI Emperor:
+    https://uwsgi-docs.readthedocs.io/en/latest/Emperor.html
+.. _uwsgi ini file:
+   https://uwsgi-docs.readthedocs.io/en/latest/Configuration.html#ini-files
+.. _systemd unit template:
+   http://0pointer.de/blog/projects/instances.html
+
+
+Origin uWSGI
+============
+
+How uWSGI is implemented by distributors is different.  uWSGI itself
+recommend two methods
+
+`systemd.unit`_ template files as described here `One service per app in systemd`_.
+
+  There is one `systemd unit template`_ and one `uwsgi ini file`_ per uWSGI-app
+  placed at dedicated locations.  Take archlinux and a searx.ini as example::
+
+    unit template    -->  /usr/lib/systemd/system/uwsgi@.service
+    uwsgi ini files  -->  /etc/uwsgi/searx.ini
+
+  The searx app can be maintained as know from common systemd units::
+
+    systemctl enable  uwsgi@searx
+    systemctl start   uwsgi@searx
+    systemctl restart uwsgi@searx
+    systemctl stop    uwsgi@searx
+
+The `uWSGI Emperor`_ mode which fits for maintaining a large range of uwsgi apps.
+
+  The Emperor mode is a special uWSGI instance that will monitor specific
+  events.  The Emperor mode (service) is started by a (common, not template)
+  systemd unit.  The Emperor service will scan specific directories for `uwsgi
+  ini file`_\s (also know as *vassals*).  If a *vassal* is added, removed or the
+  timestamp is modified, a corresponding action takes place: a new uWSGI
+  instance is started, reload or stopped.  Take Fedora and a searx.ini as
+  example::
+
+    to start a new searx instance create   --> /etc/uwsgi.d/searx.ini
+    to reload the instance edit timestamp  --> touch /etc/uwsgi.d/searx.ini
+    to stop instance remove ini            --> rm /etc/uwsgi.d/searx.ini
+
+Distributors
+============
+
+The `uWSGI Emperor`_ mode and `systemd unit template`_ is what the distributors
+mostly offer their users, even if they differ in the way they implement both
+modes and their defaults.  Another point they might differ is the packaging of
+plugins (if so, compare :ref:`install packages`) and what the default python
+interpreter is (python2 vs. python3).
+
+Fedora starts a Emperor by default, while archlinux does not start any uwsgi
+service by default.  Worth to know; debian (ubuntu) follow a complete different
+approach.  *debian*: your are familiar with the apache infrastructure? .. they
+do similar for the uWSGI infrastructure (with less comfort), the folders are::
+
+    /etc/uwsgi/apps-available/
+    /etc/uwsgi/apps-enabled/
+
+The `uwsgi ini file`_ is enabled by a symbolic link::
+
+  ln -s /etc/uwsgi/apps-available/searx.ini /etc/uwsgi/apps-enabled/
+
+From debian's documentation (``/usr/share/doc/uwsgi/README.Debian.gz``): You
+could control specific instance(s) by issuing::
+
+  service uwsgi <command> <confname> <confname> ...
+
+  sudo -H service uwsgi start searx
+  sudo -H service uwsgi stop  searx
+
+My experience is, that this command is a bit buggy.
+
+Alltogether
+===========
+
 Create the configuration ini-file according to your distribution (see below) and
 restart the uwsgi application.