senseless

NOTE: This is currently in a state where it is probably not very useful for other people, but I'll try to improve on this. It is still a bit of a hacky project.

What does this do?

I wanted to have a very simple way in order to push sensor values from a environmental monitoring station to a central location, where these values could be retrieved as JSON in order to display them on a local web site. All values are also scraped from this and pushed into a graphite database.

Current state

Autumn 2020: This thing has been running on a local server for a bit over a year now, with, at times, several months of uptime (meaning that I did not restart the server after kernel updates — shame on me!).

Features

Flexible configuration
Protecting end-points with simple tokens for writing and optionally reading
Dumps data periodically and on shutdown
Indicate if values are stale (not updated after exceeding lifetime)
Format values, adding an offset, scaling them, etc.
…

Non-Goals

Retaining historical data beyond some min / max / average values for the last 24 hours (think weather station)
Generally doing too much

Examples

Configuration (collections.json)

[
  {
    "path": "/weather",
    "writeToken": "7d8e034d-6f90-42ad-a98b-152383f4eac9",
    "valueConfig": [
      {
        "path": "/nc2.5",
	"lifetime": 30

      },
      {
        "path": "/temperature",
        "format": "0.0",
        "scale": 0.01,
	"lifetime": 30

      },
      {
        "path": "/humidity",
        "format": "0.0",
        "scale": 0.001,
	"lifetime": 30

      },
      {
        "path": "/pressure",
        "format": "0.00",
        "scale": 0.001,
	"lifetime": 30

      },
      {
        "path": "/co2",
        "type": "INTEGER",
	"lifetime": 30

      }
    ]
  }
]

Which may return values such as the following when queried via curl --silent http://localhost:7000/weather/.

{
  "/co2": {
    "timestamp": {
      "nano": 844653000,
      "epochSecond": 1600376332
    },
    "lifetime": 30,
    "rawValue": 428,
    "rawMax": 509,
    "rawMin": 346,
    "value": "428",
    "min": "346",
    "max": "509",
    "unformattedValue": 428,
    "stale": false,
    "age": 5
  },
  "/pressure": {
    "timestamp": {
      "nano": 282272000,
      "epochSecond": 1600375749
    },
    "lifetime": 30,
    "rawValue": 1008791,
    "rawMax": 1008981,
    "rawMin": 1007548,
    "value": "1008.79",
    "min": "1007.55",
    "max": "1008.98",
    "unformattedValue": 1008.791,
    "stale": true,
    "age": 588
  },
  "/temperature": {
    "timestamp": {
      "nano": 246501000,
      "epochSecond": 1600375749
    },
    "lifetime": 30,
    "rawValue": 2185,
    "rawMax": 2387,
    "rawMin": 2061,
    "value": "21.9",
    "min": "20.6",
    "max": "23.9",
    "unformattedValue": 21.85,
    "stale": true,
    "age": 588
  },
  "/humidity": {
    "timestamp": {
      "nano": 316782000,
      "epochSecond": 1600375749
    },
    "lifetime": 30,
    "rawValue": 59056,
    "rawMax": 79302,
    "rawMin": 57998,
    "value": "59.1",
    "min": "58.0",
    "max": "79.3",
    "unformattedValue": 59.056000000000004,
    "stale": true,
    "age": 588
  },
  "/nc2.5": {
    "timestamp": {
      "nano": 234946000,
      "epochSecond": 1600376330
    },
    "lifetime": 30,
    "rawValue": 50.23,
    "rawMax": 93.61,
    "rawMin": 37.51,
    "value": "50.23",
    "min": "37.51",
    "max": "93.61",
    "unformattedValue": 50.23,
    "stale": false,
    "age": 7
  }
}

Updating a value via curl may look like this curl -d "1234" -X POST http://localhost:7000/weather/pressure?token=7d8e034d-6f90-42ad-a98b-152383f4eac9.