class MqttBus(IBus):
"""
Args transport from pusher to subscribers via MQTT
"""
_subscribers = dict()
def __init__(self,
host=None,
*args,
publish_time_out=0.05,
publish_waiting=0.1,
mid_max_len=64,
qos=2,
retain=True,
**kwargs):
super().__init__()
if host is None:
host = 'localhost'
self.client = Client(*args, **kwargs)
self.client.connect(host)
self.client.loop_start()
self.client.on_publish = self._on_publish
self._received_messages = []
self.mid_max_len = mid_max_len
self.publish_time_out = publish_time_out
self.publish_waiting = publish_waiting
self.qos = qos
self.retain = retain
@staticmethod
def _loads(payload):
try:
return pickle.loads(payload,
fix_imports=True,
encoding="utf-8",
errors="strict")
except Exception as e:
log.error('mqtt loads error:' + str(e))
return None
@staticmethod
def _dumps(data):
try:
return pickle.dumps(data, protocol=3, fix_imports=True)
except Exception as e:
log.error('mqtt dumps error:' + str(e))
return None
def _on_publish(self, client, userdata, mid):
if len(self._received_messages) >= self.mid_max_len:
self._received_messages.pop(0)
self._received_messages.append(mid)
else:
self._received_messages.append(mid)
def _on_message(self, client, userdata, msg):
args, kwargs = self._loads(msg.payload)
if self._subscribers.get(msg.topic):
for fn in self._subscribers[msg.topic]:
fn(*args, **kwargs)
else:
log.warning(
'mqtt Callback _subscribers is not set for topic={}'.format(
msg.topic))
def subscribe(self, topic, fn=None):
"""
Add function fn to subscribers list
"""
if fn:
assert hasattr(fn, '__call__')
self.client.subscribe(topic, qos=self.qos)
self.client.message_callback_add(
topic, lambda client, userdata, msg: self._on_message(
client, userdata, msg))
if self._subscribers.get(topic) is None:
self._subscribers[topic] = [fn]
log.info('mqtt Function {} subscribed to topic "{}"'.format(
fn.__name__, topic))
else:
self._subscribers[topic].append(fn)
log.info('mqtt Function {} subscribed to topic "{}"'.format(
fn.__name__, topic))
else:
self.client.message_callback_remove(topic)
self.client.unsubscribe(topic)
def push(self, topic, *args, **kwargs):
"""
Call all the subscribers
"""
_args = [arg for arg in args if isinstance(arg, (float, int, str))]
_kwargs = {
key: arg
for key, arg in kwargs.items()
if isinstance(arg, (float, int, str))
}
if _args or _kwargs:
log.debug(
'pushed topic "{}" with args {} and kwargs {} and {}'.format(
topic, str(_args), str(_kwargs),
str(set(kwargs.keys()) - set(_kwargs.keys()))))
send_data = self._dumps((args, kwargs))
log.info('mqtt Pushing data with size={} to topic={}...'.format(
len(send_data), topic))
rc, mid = self.client.publish(topic,
send_data,
qos=self.qos,
retain=self.retain)
publish_time = time.time()
while mid not in self._received_messages:
time.sleep(self.publish_time_out)
if (time.time() - publish_time) >= self.publish_waiting:
break
if rc == 0:
log.info('mqtt Pushed data to topic={} with rc {}'.format(
topic, rc))
else:
log.warning('mqtt Not pushed data to topic={} with rc {}'.format(
topic, rc))
