Creating a python service or daemon with Circus
In this guide we'll be using Circus to start and persist python services. Circus can ensure that the process restarts if killed, or that a requisite number of worker threads run and even provide hooks and other advanced features.
Let's install Circus, for most platforms this should be as simple as installing through Pip.
pip3 install circus
Now, I'm going to adopt the Nginx & Uwsgi approach here of using an 'available folder and symlinking things on into 'enabled folder, so for us it'll be scripts-available and scripts-enabled. This enables you to easily turn services on or off, whilst maintaining the config.
mkdir -p /etc/circus/scripts-available /etc/circus/scripts-enabled /var/log/circus
[circus] check_delay = 5 endpoint = tcp://127.0.0.1:5555 pubsub_endpoint = tcp://127.0.0.1:5556 include = scripts-enabled/*.ini umask = 002
[Unit] Description=Circus process manager After=syslog.target network.target nss-lookup.target [Service] Type=simple ExecReload=/usr/local/bin/circusctl reload ExecStart=/usr/local/bin/circusd /etc/circus/circus.ini Restart=always RestartSec=5 [Install] WantedBy=default.target
Create a service
[watcher:widgets_controller] working_dir = /srv/widgets/ uid = 1000 gid = 1001 cmd = venv-bottle/bin/python3 args = -u controller.py $(circus.wid) $(CIRCUS.ENV.VAR) warmup_delay = 0 numprocesses = 1 # will push in test.log the stream every 300 ms stdout_stream.class = FileStream stdout_stream.filename = /var/log/circus/widgets_controller.log stderr__stream.class = FileStream stderr_stream.filename = /var/log/circus/widgets_controller.err # optionally rotate the log file when it reaches 1 gb # and save 5 copied of rotated files stdout_stream.max_bytes = 1073741824 stdout_stream.backup_count = 5
Gotchas The paths will need to be specified as absolute for the logs, and unless you specify
working_dir for the watcher, so will the pythonscript (and/or virtual environment), and of course the application won't be pwd in its own path, hence it's strongly recommended to specify
Here's what you should have:
Activate your service
Now to enable widgets:
[email protected]:~#: ln -s /etc/circus/scripts-available/widgets.ini /etc/circus/scripts-enabled/widgets.ini [email protected]:~# circusctl start widgets_controller [email protected]:~# circusctl status widgets_controller: active
And your service should be running. Any error information or output will be in /var/log/circus/widgets_controller.*