gearchange.py

#!/usr/bin/python2

import os,sys,argparse
import paho.mqtt.client as mqtt

import mdns_resolver

dirname = os.path.dirname(os.path.abspath(__file__))
nodename = "unknown-node"
force_check_topic = "gearchange-force-check"

gear_num = 0
subscribe_mid = None

def shutdown_system():
  print "Executing shutdown script..."
  script = os.path.join(dirname, "shutdown.sh")
  if os.path.isfile(script) and os.system(script) == 0: sys.exit(0)

def start_job():
  print "Executing startup script..."
  script = os.path.join(dirname, "startup.sh")
  if not os.path.isfile(script) or os.system(script) != 0:
    print "Failed to execute startup.sh"

def gear_up():
  global gear_num
  script = os.path.join(dirname, "gear%d.sh" % (gear_num + 1))
  if not os.path.isfile(script) or os.system(script) != 0: return
  #else
  gear_num += 1
  print "gear up:%d" % gear_num

def gear_down():
  global gear_num
  if gear_num <= 1: return
  #else
  script = os.path.join(dirname, "gear%d.sh" % (gear_num - 1))
  if not os.path.isfile(script) or os.system(script) != 0: return
  #else
  gear_num -= 1
  print "gear down:%d" % gear_num

def on_connect(client, userdata, flags, response_code):
  global subscribe_mid, nodename
  topic = "gearchange-" + nodename
  result, subscribe_mid = client.subscribe(topic)
  if result != mqtt.MQTT_ERR_SUCCESS:
    print "Could not subscribe %s" % topic
  print "MQTT connected. nodename=%s" % nodename

def on_subscribe(client, userdata, mid, granted_qos):
  global subscribe_mid
  if mid != subscribe_mid: return
  #else
  client.publish(force_check_topic, "check")

def on_message(client, userdata, msg):
  global gear_num
  if msg.topic != "gearchange-" + nodename: return
  msg = str(msg.payload)
  if gear_num == 0:
    if msg == "down": shutdown_system()
    else: 
      start_job()
      gear_num = 1
    return
  #else
  if msg == "up": gear_up()
  elif msg == "down": gear_down()

if __name__ == '__main__':
  parser = argparse.ArgumentParser()
  parser.add_argument("nodename", type = str)
  parser.add_argument("--mqtt-host", type = str)
  parser.add_argument("-p", "--port", type = int, default=1883)
  args = parser.parse_args()
  nodename = args.nodename

  client = mqtt.Client(protocol=mqtt.MQTTv311)

  client.on_connect = on_connect
  client.on_subscribe = on_subscribe
  client.on_message = on_message

  if args.mqtt_host is None:
    print "Discovering MQTT service..."
    host_and_port = mdns_resolver.resolve("_mqtt._tcp.local.")
    if host_and_port is None:
      print "No MQTT sevice in network."
      sys.exit(1)
    #else
    print "Found."
    host,port = host_and_port
  else:
    host,port = args.mqtt_host, args.port

  client.connect(host, port=port, keepalive=60)

  client.loop_forever()