This is a Ruby implementation of a PID Controller. A PID controller is a feedback system that is configured with a target setpoint, can read measurements of the system to see how close we are to the setpoint, and will omit an output. Every day examples include:
- Cruise control
- Quadcopters (appearently, because they predominate search results)
- Database load (yay! This is why the purpose I'm actually writing this for).
I mentioned databases, so here's an example of how we can prevent a low priority task (e.g. bulk deletion) from contending with customer traffic:
sensor = MySQLSensor.new # Use your imagination controller = PIDController.new( setpoint: 60.0, kp: 5.0, ki: 1.0, kd: 0.1, output_max: 0.0, integral_max: 0.0 ) Event.where(account_id: account_id).in_batches do |relation| relation.delete_all backoff = -1 * controller << sensor.cpu_utilization sleep backoff if backoff > 0 end
After checking out the repo, run
bin/setup to install dependencies. Then, run
rake spec to run the tests. You can also run
bin/console for an interactive prompt that will allow you to experiment.
Bug reports and pull requests are welcome on GitHub at https://github.com/gabetax/pid_controller.