Implementation of the presence tracker backend

[jonasspinner]

Presence Tracker System

Requirements

• Users should be able to
  • register their devices with their MAC addresses and
  • delete registered devices.
• The presence of a user is concluded by the activity of its devices.
• The analyses of the aggregated presence by time and weekday should be possible.

Objects

• User: a person using the system. Connected to a slack account.
• Team: several users are in a team.
• Presence: a period a user is present at the launchpad.
• Device: a device owned by a user.
• Activity: an activity of a device within a monotoring interval.
• Dump: all activities within the same monotoring interval.

Data discretion

The data is blurred by the size of the monotoring intervals and grouping of active intervals to a presence period. Also presence is only correlated to the user and not a single device.

• interval-time: Size of monotoring intervals. Example: 5 minutes.
• union-time: Maximum gap between activities to be considered part of the same presence. Example: 30 minutes.

Algorithm

The algorithm used to conclude from device activity to user presence.

for all hashes:
  device := {device with the hash}
  if device exists:
    user := {owner of the device}
    last_presence := {last presence from the user}
    if last_present exists && last_presence is younger than union_time:
      update last_presence
    else:
      add new presence from the user

Presence Tracker Client

The client gathers the information, transforms it and sends it to the server. The github project for the client can be found here.

API Endpoint

Every monotoring interval the active devices in the vicinity of a client are recorded and encoded as a SHA256 hash value of the MAC Address. The hash values are sent to the API Endpoint via a HTTP POST request.

Example

POST /activities HTTP/1.1
{
  "activities": [
    {
      "hash": "5fbf2c53d0ab6895cf8a5133d7b2a0bd5bba954f033bffaba87b40892fe71b03"
    },
    ...
    {
      "hash": "84f6408053b4d7998140d01a4c620ccc273557b2d1d366b3239c199ca91abd3b"
    }
  ],
  "date": "2016-12-01T18:38:48.447607"
}

HTTP/1.1 201 Created
{
  "success": true
}