farmbot_os/docs/project/farmbot_ext.md

FarmBot Ext OTP App

the farmbot_ext OTP app contains extended FarmbotCore functionality. This includes mostly network functionality that isn't possible to do in farmbot_core.

Bootstrap subsystem

Subsystem responsible for bootstrapping a connection to the FarmBot network services. This includes authenticating with the FarmBot API, connecting to AMQP/MQTT and syncing the bare minimum resources to get up and running.

HTTP/Sync subsystem

This is the subsystem that syncronizes FarmBot with the remote API. It uses HTTP to download an index of all the data FarmBot cares about, and compares timestamps to determine who has the most up to date data. The basic flow is whoever has the most recent updated_at field will become the "most truthy". If FarmBot has a more recent updated_at field, FarmBot will do an HTTP PUT of it's data. If the remote resource does not exist, FarmBot will do an HTTP POST of it's data. If the remote data has a more recent updated_at field, FarmBot will do an HTTP GET and replace it's own data.

AMQP/MQTT substem

FarmBot maintains a connection to the API for real time communication. This real time communication connection is multiplexed over multiple channels. Below is a description of the channels

• bot_state - pushes a JSON encoded version of the bot_state process (from farmbot_core)
• celery_script - receives/sends JSON encoded celery_script. Used for controling FarmBot externally
• log - sends log messages from farmbot_core's logger
• ping/pong - echos everything received. used for detecting active conncetion
• auto_sync - the API dispatches every REST resource change on this channel. Used to speed up HTTP requests
• telemetry - similar to the log channel, but sends consumable events, rather than human readable messages

Image uploader subsystem

This subsystem watches a local directory, and as matching files appear in that directory, it uploads them using the FarmBot image upload protocol. Basically an HTTP request to fetch credentials that are used to preform another HTTP request to upload the photo.