Minimalist NodeMCU application that sends GEFL logs to Graylog2

init.lua

mqtt_connected = false
source = 'NodeMCU' .. node.chipid()
data = {
  version = '1.1',
  source = source,
  short_message = 'Sensor data (temperature and pressure)',
  _temperature = 0,
  _pressure = 0
}

-- This function is called when WiFi connection is established
function start()
  -- initialize MQTT client
  local m = mqtt.Client()
  m:connect("<mqtt-server>", 1883, 0, 1, function()
    mqtt_connected = true
    print("MQTT Connected")
  end)

  -- initialize BMP085 sensor
  bmp085.init(2, 1)
  
  -- every second read sensor values and publish them
  -- onto system/logs in the form of a GEFL-formatted message
  tmr.create():alarm(1000, tmr.ALARM_AUTO, function()
    data._temperature = bmp085.temperature()
    data._pressure = bmp085.pressure()
    if mqtt_connected then
      print("Sending MQTT GELF log")
      m:publish("system/logs", cjson.encode(data), 0, 0)
    else
      print("MQTT not connected")
    end
  end)
end

-- Connect to access point
wifi.setmode(wifi.STATION)
wifi.sta.config("<SSID>", "<password>")
wifi.sta.eventMonReg(wifi.STA_GOTIP, function()
  print("WIFI Connected " .. wifi.sta.getip())
  wifi.sta.eventMonStop()
  start()
end)
wifi.sta.eventMonStart()