uWSGI¶
Origin uWSGI¶
How uWSGI is implemented by distributors varies. The uWSGI project itself recommends two methods:
systemd.unit template file as described here One service per app in systemd:
There is one systemd unit template on the system installed and one uwsgi ini file per uWSGI-app placed at dedicated locations. Take archlinux and a
searxng.ini
as example:systemd template unit: /usr/lib/systemd/system/uwsgi@.service contains: [Service] ExecStart=/usr/bin/uwsgi --ini /etc/uwsgi/%I.ini SearXNG application: /etc/uwsgi/searxng.ini links to: /etc/uwsgi/apps-available/searxng.iniThe SearXNG app (template
/etc/uwsgi/%I.ini
) can be maintained as known from common systemd units:$ systemctl enable uwsgi@searxng $ systemctl start uwsgi@searxng $ systemctl restart uwsgi@searxng $ systemctl stop uwsgi@searxng
The uWSGI Emperor which fits for maintaining a large range of uwsgi apps and there is a Tyrant mode to secure multi-user hosting.
The Emperor mode is a special uWSGI instance that will monitor specific events. The Emperor mode (the service) is started by a (common, not template) systemd unit.
The Emperor service will scan specific directories for uwsgi ini files (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
searxng.ini
as example:to install & start SearXNG instance create --> /etc/uwsgi.d/searxng.ini to reload the instance edit timestamp --> touch /etc/uwsgi.d/searxng.ini to stop instance remove ini --> rm /etc/uwsgi.d/searxng.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 in is the packaging of plugins (if so, compare Install packages) and what the default python interpreter is (python2 vs. python3).
While archlinux does not start a uWSGI service by default, Fedora (RHEL) starts a Emperor in Tyrant mode by default (you should have read Pitfalls of the Tyrant mode). Worth to know; debian (ubuntu) follow a complete different approach, read see Debian’s uWSGI layout.
Debian’s uWSGI layout¶
Be aware, Debian’s uWSGI layout is quite different from the standard uWSGI configuration. Your are familiar with Debian’s Apache layout? .. they do a similar thing for the uWSGI infrastructure. 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/searxng.ini /etc/uwsgi/apps-enabled/
More details can be found in the uwsgi.README.Debian
(/usr/share/doc/uwsgi/README.Debian.gz
). Some commands you should know on
Debian:
Commands recognized by init.d script
====================================
You can issue to init.d script following commands:
* start | starts daemon
* stop | stops daemon
* reload | sends to daemon SIGHUP signal
* force-reload | sends to daemon SIGTERM signal
* restart | issues 'stop', then 'start' commands
* status | shows status of daemon instance (running/not running)
'status' command must be issued with exactly one argument: '<confname>'.
Controlling specific instances of uWSGI
=======================================
You could control specific instance(s) by issuing:
SYSTEMCTL_SKIP_REDIRECT=1 service uwsgi <command> <confname> <confname>...
where:
* <command> is one of 'start', 'stop' etc.
* <confname> is the name of configuration file (without extension)
For example, this is how instance for /etc/uwsgi/apps-enabled/hello.xml is
started:
SYSTEMCTL_SKIP_REDIRECT=1 service uwsgi start hello
uWSGI maintenance¶
# init.d --> /usr/share/doc/uwsgi/README.Debian.gz
# For uWSGI debian uses the LSB init process, this might be changed
# one day, see https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=833067
create /etc/uwsgi/apps-available/searxng.ini
enable: sudo -H ln -s /etc/uwsgi/apps-available/searxng.ini /etc/uwsgi/apps-enabled/
start: sudo -H service uwsgi start searxng
restart: sudo -H service uwsgi restart searxng
stop: sudo -H service uwsgi stop searxng
disable: sudo -H rm /etc/uwsgi/apps-enabled/searxng.ini
# systemd --> /usr/lib/systemd/system/uwsgi@.service
# For uWSGI archlinux uses systemd template units, see
# - http://0pointer.de/blog/projects/instances.html
# - https://uwsgi-docs.readthedocs.io/en/latest/Systemd.html#one-service-per-app-in-systemd
create: /etc/uwsgi/searxng.ini
enable: sudo -H systemctl enable uwsgi@searxng
start: sudo -H systemctl start uwsgi@searxng
restart: sudo -H systemctl restart uwsgi@searxng
stop: sudo -H systemctl stop uwsgi@searxng
disable: sudo -H systemctl disable uwsgi@searxng
# systemd --> /usr/lib/systemd/system/uwsgi.service
# The unit file starts uWSGI in emperor mode (/etc/uwsgi.ini), see
# - https://uwsgi-docs.readthedocs.io/en/latest/Emperor.html
create: /etc/uwsgi.d/searxng.ini
restart: sudo -H touch /etc/uwsgi.d/searxng.ini
disable: sudo -H rm /etc/uwsgi.d/searxng.ini
uWSGI setup¶
Create the configuration ini-file according to your distribution and restart the uwsgi application. As shown below, the Installation Script installs by default:
a uWSGI setup that listens on a socket and
enables cache busting.
# -*- mode: conf; coding: utf-8 -*-
[uwsgi]
# uWSGI core
# ----------
#
# https://uwsgi-docs.readthedocs.io/en/latest/Options.html#uwsgi-core
# Who will run the code / Hint: in emperor-tyrant mode uid & gid setting will be
# ignored [1]. Mode emperor-tyrant is the default on fedora (/etc/uwsgi.ini).
#
# [1] https://uwsgi-docs.readthedocs.io/en/latest/Emperor.html#tyrant-mode-secure-multi-user-hosting
#
uid = searxng
gid = searxng
# set (python) default encoding UTF-8
env = LANG=C.UTF-8
env = LANGUAGE=C.UTF-8
env = LC_ALL=C.UTF-8
# chdir to specified directory before apps loading
chdir = /usr/local/searxng/searxng-src/searx
# SearXNG configuration (settings.yml)
env = SEARXNG_SETTINGS_PATH=/etc/searxng/settings.yml
# disable logging for privacy
disable-logging = true
# The right granted on the created socket
chmod-socket = 666
# Plugin to use and interpreter config
single-interpreter = true
# enable master process
master = true
# load apps in each worker instead of the master
lazy-apps = true
# load uWSGI plugins
plugin = python3,http
# By default the Python plugin does not initialize the GIL. This means your
# app-generated threads will not run. If you need threads, remember to enable
# them with enable-threads. Running uWSGI in multithreading mode (with the
# threads options) will automatically enable threading support. This *strange*
# default behaviour is for performance reasons.
enable-threads = true
# Number of workers (usually CPU count)
workers = %k
threads = 4
# plugin: python
# --------------
#
# https://uwsgi-docs.readthedocs.io/en/latest/Options.html#plugin-python
# load a WSGI module
module = searx.webapp
# set PYTHONHOME/virtualenv
virtualenv = /usr/local/searxng/searx-pyenv
# add directory (or glob) to pythonpath
pythonpath = /usr/local/searxng/searxng-src
# speak to upstream
# -----------------
socket = /usr/local/searxng/run/socket
buffer-size = 8192
# uWSGI serves the static files and in settings.yml we use::
#
# ui:
# static_use_hash: true
#
static-map = /static=/usr/local/searxng/searxng-src/searx/static
# expires set to one day
static-expires = /* 86400
static-gzip-all = True
offload-threads = %k
# -*- mode: conf; coding: utf-8 -*-
[uwsgi]
# uWSGI core
# ----------
#
# https://uwsgi-docs.readthedocs.io/en/latest/Options.html#uwsgi-core
# Who will run the code
uid = searxng
gid = searxng
# set (python) default encoding UTF-8
env = LANG=C.UTF-8
env = LANGUAGE=C.UTF-8
env = LC_ALL=C.UTF-8
# chdir to specified directory before apps loading
chdir = /usr/local/searxng/searxng-src/searx
# SearXNG configuration (settings.yml)
env = SEARXNG_SETTINGS_PATH=/etc/searxng/settings.yml
# disable logging for privacy
logger = systemd
disable-logging = true
# The right granted on the created socket
chmod-socket = 666
# Plugin to use and interpreter config
single-interpreter = true
# enable master process
master = true
# load apps in each worker instead of the master
lazy-apps = true
# load uWSGI plugins
plugin = python
# By default the Python plugin does not initialize the GIL. This means your
# app-generated threads will not run. If you need threads, remember to enable
# them with enable-threads. Running uWSGI in multithreading mode (with the
# threads options) will automatically enable threading support. This *strange*
# default behaviour is for performance reasons.
enable-threads = true
# Number of workers (usually CPU count)
workers = %k
threads = 4
# plugin: python
# --------------
#
# https://uwsgi-docs.readthedocs.io/en/latest/Options.html#plugin-python
# load a WSGI module
module = searx.webapp
# set PYTHONHOME/virtualenv
virtualenv = /usr/local/searxng/searx-pyenv
# add directory (or glob) to pythonpath
pythonpath = /usr/local/searxng/searxng-src
# speak to upstream
# -----------------
socket = /usr/local/searxng/run/socket
buffer-size = 8192
# uWSGI serves the static files and in settings.yml we use::
#
# ui:
# static_use_hash: true
#
static-map = /static=/usr/local/searxng/searxng-src/searx/static
# expires set to one day
static-expires = /* 86400
static-gzip-all = True
offload-threads = %k
# -*- mode: conf; coding: utf-8 -*-
[uwsgi]
# uWSGI core
# ----------
#
# https://uwsgi-docs.readthedocs.io/en/latest/Options.html#uwsgi-core
# Who will run the code / Hint: in emperor-tyrant mode uid & gid setting will be
# ignored [1]. Mode emperor-tyrant is the default on fedora (/etc/uwsgi.ini).
#
# [1] https://uwsgi-docs.readthedocs.io/en/latest/Emperor.html#tyrant-mode-secure-multi-user-hosting
#
uid = searxng
gid = searxng
# set (python) default encoding UTF-8
env = LANG=C.UTF-8
env = LANGUAGE=C.UTF-8
env = LC_ALL=C.UTF-8
# chdir to specified directory before apps loading
chdir = /usr/local/searxng/searxng-src/searx
# SearXNG configuration (settings.yml)
env = SEARXNG_SETTINGS_PATH=/etc/searxng/settings.yml
# disable logging for privacy
disable-logging = true
# The right granted on the created socket
chmod-socket = 666
# Plugin to use and interpreter config
single-interpreter = true
# enable master process
master = true
# load apps in each worker instead of the master
lazy-apps = true
# load uWSGI plugins
plugin = python3,http
# By default the Python plugin does not initialize the GIL. This means your
# app-generated threads will not run. If you need threads, remember to enable
# them with enable-threads. Running uWSGI in multithreading mode (with the
# threads options) will automatically enable threading support. This *strange*
# default behaviour is for performance reasons.
enable-threads = true
# Number of workers (usually CPU count)
workers = %k
threads = 4
# plugin: python
# --------------
#
# https://uwsgi-docs.readthedocs.io/en/latest/Options.html#plugin-python
# load a WSGI module
module = searx.webapp
# set PYTHONHOME/virtualenv
virtualenv = /usr/local/searxng/searx-pyenv
# add directory (or glob) to pythonpath
pythonpath = /usr/local/searxng/searxng-src
# speak to upstream
# -----------------
socket = /usr/local/searxng/run/socket
buffer-size = 8192
# uWSGI serves the static files and in settings.yml we use::
#
# ui:
# static_use_hash: true
#
static-map = /static=/usr/local/searxng/searxng-src/searx/static
# expires set to one day
static-expires = /* 86400
static-gzip-all = True
offload-threads = %k
Pitfalls of the Tyrant mode¶
The implementation of the process owners and groups in the Tyrant mode is
somewhat unusual and requires special consideration. In Tyrant mode mode the
Emperor will run the vassal using the UID/GID of the vassal configuration file
(user and group of the app .ini
file).
Without option emperor-tyrant-initgroups=true
in /etc/uwsgi.ini
the
process won’t get the additional groups, but this option is not available in
2.0.x branch (see #2099@uWSGI) the feature #752@uWSGI has been merged (on
Oct. 2014) to the master branch of uWSGI but had never been released; the last
major release is from Dec. 2013, since the there had been only bugfix releases
(see #2425uWSGI). To shorten up:
In Tyrant mode, there is no way to get additional groups, and the uWSGI process misses additional permissions that may be needed.
For example on Fedora (RHEL): If you try to install a redis DB with socket communication and you want to connect to it from the SearXNG uWSGI, you will see a Permission denied in the log of your instance:
ERROR:searx.redisdb: [searxng (993)] can't connect redis DB ...
ERROR:searx.redisdb: Error 13 connecting to unix socket: /usr/local/searxng-redis/run/redis.sock. Permission denied.
ERROR:searx.plugins.limiter: init limiter DB failed!!!
Even if your searxng user of the uWSGI process is added to additional groups to give access to the socket from the redis DB:
$ groups searxng
searxng : searxng searxng-redis
To see the effective groups of the uwsgi process, you have to look at the status of the process, by example:
$ ps -aef | grep '/usr/sbin/uwsgi --ini searxng.ini'
searxng 93 92 0 12:43 ? 00:00:00 /usr/sbin/uwsgi --ini searxng.ini
searxng 186 93 0 12:44 ? 00:00:01 /usr/sbin/uwsgi --ini searxng.ini
Here you can see that the additional “Groups” of PID 186 are unset (missing gid
of searxng-redis
):
$ cat /proc/186/task/186/status
...
Uid: 993 993 993 993
Gid: 993 993 993 993
FDSize: 128
Groups:
...