7.1. Fermentrack Architecture


Rewrite/fix architecture.rst to match the mkdocs/markdown version

The Fermentrack stack is based on a front end application, a controller, and a firmware running on the device that handles reading temperatures, switching cooling and heating etc. Everything but the firmware part is running under a process manager which takes care of launching the front end and brewpi.py controller scripts.

![Fermentrack Architecture](img/fermentrack.png)

See [components](components.md) documentation for links and licenses.

## The webserver nginx and chaussette WSGI server

Used to proxy http requests to chaussette over WSGI to the Fermentrack django application.

## cron

Used to start the Fermentrack stack, it starts the Circus process manager via a @reboot job, it also checks the status of circus every 10 seconds, if it not running it will start it. All this is handled by a script: updateCronCircus.sh

Supports the following arguments: {start|stop|status|startifstopped|add2cron} where:

  • start - will start circusd and all the services
  • stop - will quit circusd and all processes (note it would be started again in 10 minutes)
  • status - will output a status of all processes running (see below)
  • startifstopped - will start the process manager if stopped (called from cron every 10 minutes)
  • add2cron - if crontab entries are missing, it will add them back.

Crontab entries added with add2cron:

@reboot ~/fermentrack/brewpi-script/utils/updateCronCircus.sh start
*/10 * * * * ~/fermentrack/brewpi-script/utils/updateCronCircus.sh startifstopped

Example status output:

$ ~/fermentrack/brewpi-script/utils/updateCronCircus.sh status Fermentrack: active brewpi-spawner: active circusd-stats: active dev-brewpi1: active

## The process manager circus

Fermentrack is started at boot with the help of cron (see cron), the process manager handles all the different processes needed by Fermentrack.

  • Fermentrack - The django application (web interface) runs under chaussette
  • brewpi-spawner - An internal Fermentrack process for spawning controller scripts for controlling controllers like brewpi-esp8266.
  • circusd-stats - An Internal circus process for stats, not used yet.
  • dev-brewpi1 - Is a controller script spawned by brewpi-spawner, handing a controller.

Circus documentation can be found here.

## Logging

  • Circus process manager logs:
    • /home/fermentrack/fermentrack/log/circusd.log
  • Controller script (brewpi.py) log:
    • /home/fermentrack/fermentrack/log/dev-[name]-stdout.log
  • Controller script (brewpi.py) error/info log:
    • /home/fermentrack/fermentrack/log/dev-[name]-stderr.log
  • Controller script spawner:
    • /home/fermentrack/fermentrack/log/fermentrack-brewpi-spawner.log
  • Fermentrack django application:
    • /home/fermentrack/fermentrack/log/fermentrack.log

Logs are rotated every 2MB and the last 5 are saved with a number suffix.