Running/start-up

To check if the queen is running use ps:

ps aux | grep queen.py

While the queen is running, it will output stderr and stdout messages to /home/pi/logs/ in a filename containing the date and time the queen started.

To start the queen if it's not running:

cd /home/pi/Repositories/cbs-ntcore/pi_beehive_monitoring/scripts/
./run_queen.sh

This will start the queen and setup a crontab entry to automatically restart the queen on reboot.

Overview of system

The purpose of this system is to capture short videos (and save them for offline analysis) of many bee hive colonies as they develop. A single control computer (queen) is used to configure one or more (in this case 15) raspberry pi systems (workers).

Queen - control computer

The queen runs a python script queen.py (tested in python 3.X) that:

• runs a web server used for interacting with the queen and commanding workers
• receives worker state updates (via http)
• copies videos from each worker to the queen
• extracts a thumbnail from the early portion of each worker video
• reports the system status to the lab monitoring service

When the queen receives the first state message for a given worker, the queen will run scripts/setup_worker.sh. To configure the worker. This script will do the following:

• rsync ssh keys
• rsync (scripts)[scripts]
• call (scripts/setup.sh)[scripts/setup.sh] on the worker
• synchronize the worker time with the queen time

The setup worker script is also used for the first configuration of a new worker computer after it has an appropriate hostname. Workers must have a hostname of the form workerN where N is some number (for example: worker10).

Worker - video recording computer

Worker actions are in part controlled by cron. A cron job setup to run on the worker every minute executes scripts/send_state.sh to transfer of a state message from the worker to the queen. This state message contains:

• current state of the worker (see below)
• disk space left on worker
• current date and time on the worker

The worker can be in one of several states:

• idle
• recording: worker will call scripts/record.sh every minute
• streaming: streaming video (see scripts/stream.sh)

Workers can only enter recording or streaming states from the idle state. The state of the worker is saved in a state file (/home/pi/state). The worker also contains a setup file (/home/pi/setup) that is created during the first setup of the worker (see (scripts/setup.sh)[scripts/setup.sh]).

Note that no more than 1 worker should be streaming at any time as streaming requires the queen to be actively receiving the video. Starting several streams might cause a worker to get stuck in a streaming state. This can be fixed by sshing into the worker, killing the raspivid process (used for streaming), then manually updating the state file or by rebooting the worker, removing the state file and re-setting up the worker.

Videos

Videos are first saved on the workers (in /home/pi/videos). If a worker drive is more than 90% full prior to recording, the worker will delete the old videos in 30 file chunks until there is enough space (see scripts/purge_videos.sh). Videos are separated into sub-directories by day and have a filename containing the worker hostname, date and time (for example: /home/pi/videos/190528/190528_153001_worker10.h264). Dates take the form of year, month, day (190528 = 28th of May, 2019). Times take the form of hour, minute, second (153001 = 1 second past 2:30 PM). Videos are saved as raw h264 streams and may need to be containerized before loading into some programs.

Once a minute (if the queen python script is running) the queen will transfer videos from all workers (using rsync) and store them in sub-directories in /home/pi/videos on the queen. Each worker will have it's own sub directory determined by it's worker number (so videos from worker 10 will be in /home/pi/videos/10).

See (scripts/record.sh)[scripts/record.sh] to change any raspivid settings for the recordings.