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Advanced Python Development Sensors

This is the data collection package that forms part of the running example for the book Advanced Python Development.

Usage

This installs a console script called sensors that returns a report on various aspects of the system. The available sensors are:

  • Python version
  • IP Addresses
  • CPU Usage
  • RAM Available
  • Battery charging state
  • Ambient Temperature
  • Ambient Humidity

There are no command-line options, to view the report run sensors on the command line.

Caveats

The Ambient Temperature and Ambient Humidity sensors are only available on RaspberryPi hosts and assume that a DHT22 sensor is connected to pin D20.

The location and type of the sensor can be controlled by setting a pair of environment variables: APD_SENSORS_TEMPERATURE_BOARD and APD_SENSORS_TEMPERATURE_PIN.

If there is an entry in /etc/hosts for the current machine's hostname that value will be the only result from the IP Addresses sensor.

Installation

You can install with pip3 install apd.sensors under Python 3.7 or higher.

We recommend using pipenv to manage your environment, in which case you would install using pipenv --three install apd.sensors and run the programme using pipenv run sensors.

API server

There is an optional API server shipped with apd.sensors. To use this you should install the apd.sensors[webapp] extra. The API can then be started with the non-production quality wsgiref server using:

python -m apd.sensors.wsgi.serve

or through Waitress (if installed) using:

waitress-serve --call apd.sensors.wsgi:set_up_config

Other WSGI servers will also work, you should use set_up_config as a factory function.

An environment variable is required to use the API server, APD_SENSORS_API_KEY should be set to the API key required to gain access. One can be generated using:

python -c "import uuid; print(uuid.uuid4().hex)"

The following endpoints are supported:

  • /v/3.0/sensors
  • /v/3.0/sensors/sensorid
  • /v/3.0/deployment_id

Historical data

You can install optional functionality to periodically store sensor values using the apd.sensors[scheduled] extra. In this case, sensors --save will store the recorded data to sensor_data.sqlite in the current working directory.

The database connection can be specified with --db sqlite:////var/sensors.sqlite, for example. It can also be specified with the APD_SENSORS_DB_URI environment variable.

The database must be migrated to contain the correct data first. This can be done by running alembic upgrade head with the following alembic.ini file in the current working directory.

[alembic]
script_location = apd.sensors:alembic
sqlalchemy.url = sqlite:///sensor_data.sqlite

Historical data API

An API to extract historical data is also available if installed with apd.sensors[webapp,scheduled,storedapi].

This provides the following three URIs, where start and end are a date/time in ISO format.

  • /v/3.0/historical
  • /v/3.0/historical/start
  • /v/3.0/historical/start/end