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uWSGI

docs/admin/installation-uwsgi.rst

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.. _searxng uwsgi:

===== uWSGI

.. sidebar:: further reading

  • systemd.unit_
  • uWSGI Emperor_

.. 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

.. _Tyrant mode: https://uwsgi-docs.readthedocs.io/en/latest/Emperor.html#tyrant-mode-secure-multi-user-hosting

How uWSGI is implemented by distributors varies. The uWSGI project itself recommends two methods:

  1. 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/[email protected]
        contains: [Service]
                  ExecStart=/usr/bin/uwsgi --ini /etc/uwsgi/%I.ini

SearXNG application:   /etc/uwsgi/searxng.ini
        links to: /etc/uwsgi/apps-available/searxng.ini

The SearXNG app (template /etc/uwsgi/%I.ini) can be maintained as known from common systemd units:

.. code:: sh

 $ systemctl enable  uwsgi@searxng
 $ systemctl start   uwsgi@searxng
 $ systemctl restart uwsgi@searxng
 $ systemctl stop    uwsgi@searxng

2. 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 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 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 :ref: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 :ref:uWSGI Tyrant mode pitfalls). Worth to know; debian (ubuntu) follow a complete different approach, read see :ref:Debian's uWSGI layout.

.. _Debian's uWSGI layout:

Debian's uWSGI layout

.. _uwsgi.README.Debian: https://salsa.debian.org/uwsgi-team/uwsgi/-/raw/debian/latest/debian/uwsgi.README.Debian

Be aware, Debian's uWSGI layout is quite different from the standard uWSGI configuration. Your are familiar with :ref: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:

.. code:: none

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:

uWSGI maintenance

.. tabs::

.. group-tab:: Ubuntu / debian

  .. kernel-include:: $DOCS_BUILD/includes/searxng.rst
     :start-after: START searxng uwsgi-description ubuntu-20.04
     :end-before: END searxng uwsgi-description ubuntu-20.04

.. hotfix: a bug group-tab need this comment

.. group-tab:: Arch Linux

  .. kernel-include:: $DOCS_BUILD/includes/searxng.rst
     :start-after: START searxng uwsgi-description arch
     :end-before: END searxng uwsgi-description arch

.. hotfix: a bug group-tab need this comment

.. group-tab:: Fedora / RHEL

  .. kernel-include:: $DOCS_BUILD/includes/searxng.rst
     :start-after: START searxng uwsgi-description fedora
     :end-before: END searxng uwsgi-description fedora

.. _uwsgi setup:

uWSGI setup

Create the configuration ini-file according to your distribution and restart the uwsgi application. As shown below, the :ref:installation scripts installs by default a uWSGI setup that listens on a socket.

.. tabs::

.. group-tab:: Ubuntu / debian

  .. kernel-include:: $DOCS_BUILD/includes/searxng.rst
     :start-after: START searxng uwsgi-appini ubuntu-20.04
     :end-before: END searxng uwsgi-appini ubuntu-20.04

.. hotfix: a bug group-tab need this comment

.. group-tab:: Arch Linux

  .. kernel-include:: $DOCS_BUILD/includes/searxng.rst
     :start-after: START searxng uwsgi-appini arch
     :end-before: END searxng uwsgi-appini arch

.. hotfix: a bug group-tab need this comment

.. group-tab:: Fedora / RHEL

  .. kernel-include:: $DOCS_BUILD/includes/searxng.rst
     :start-after: START searxng uwsgi-appini fedora
     :end-before: END searxng uwsgi-appini fedora

.. _uWSGI Tyrant mode pitfalls:

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).

.. _#2099@uWSGI: https://github.com/unbit/uwsgi/issues/2099 .. _#752@uWSGI: https://github.com/unbit/uwsgi/pull/752 .. _#2425uWSGI: https://github.com/unbit/uwsgi/issues/2425

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 valkey 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.valkeydb: [searxng (993)] can't connect valkey DB ... ERROR:searx.valkeydb: Error 13 connecting to unix socket: /usr/local/searxng-valkey/run/valkey.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 valkey DB::

$ groups searxng searxng : searxng searxng-valkey

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-valkey)::

$ cat /proc/186/task/186/status ... Uid: 993 993 993 993 Gid: 993 993 993 993 FDSize: 128 Groups: ...