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protect subscription dictionaries #28

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protect subscription dictionaries #28

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88 changes: 50 additions & 38 deletions src/upparat/mqtt.py
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
import logging
import struct
from threading import RLock

from paho.mqtt.client import Client
from paho.mqtt.client import CONNACK_ACCEPTED
Expand Down Expand Up @@ -54,6 +55,10 @@ def __init__(self, client_id, queue):
self._subscription_mid = {}
self._unsubscription_mid = {}

self._subscriptions_lock = RLock()
self._subscription_mid_lock = RLock()
self._unsubscription_mid_lock = RLock()

super().__init__(client_id)

self.on_connect = self._on_connect_handler
Expand All @@ -73,36 +78,38 @@ def subscribe(self, topic, qos=0):
# is threaded on_unsubscribe callback can be
# called before _subscribe returns here, but we
# want to know the topic in the callback (B)
message_id = self._mid_generate()
self._subscription_mid[message_id] = topic

# We still want to keep the mapping for topic - qos
# in case the error gets fixed by a reconnect later!
self._subscriptions[topic] = qos

result, _ = self._subscribe(topic, qos=qos, mid=message_id)
if result != MQTT_ERR_SUCCESS:
# Remove mid on failure
del self._subscription_mid[message_id]
logger.warning(
f"Unable to subscribe to topic {topic}: {error_string(result)}"
)
with self._subscriptions_lock and self._subscription_mid_lock:
message_id = self._mid_generate()
self._subscription_mid[message_id] = topic

# We still want to keep the mapping for topic - qos
# in case the error gets fixed by a reconnect later!
self._subscriptions[topic] = qos

result, _ = self._subscribe(topic, qos=qos, mid=message_id)
if result != MQTT_ERR_SUCCESS:
# Remove mid on failure
del self._subscription_mid[message_id]
logger.warning(
f"Unable to subscribe to topic {topic}: {error_string(result)}"
)

return result, message_id
return result, message_id

def unsubscribe(self, topic):
self._subscriptions.pop(topic, None)
with self._subscriptions_lock and self._unsubscription_mid_lock:
self._subscriptions.pop(topic, None)

# Comment (A) also applies here.
message_id = self._mid_generate()
self._unsubscription_mid[message_id] = topic
# Comment (A) also applies here.
message_id = self._mid_generate()
self._unsubscription_mid[message_id] = topic

result, _ = self._unsubscribe(topic, mid=message_id)
result, _ = self._unsubscribe(topic, mid=message_id)

if result != MQTT_ERR_SUCCESS:
del self._unsubscription_mid[message_id]
if result != MQTT_ERR_SUCCESS:
del self._unsubscription_mid[message_id]

return result, message_id
return result, message_id

def _on_connect_handler(self, _, __, ___, rc):
message = connack_string(rc)
Expand All @@ -112,8 +119,10 @@ def _on_connect_handler(self, _, __, ___, rc):
logger.error(message)

# (Re)subscribe to topics
for topic, qos in self._subscriptions.items():
self.subscribe(topic, qos=qos)

with self._subscriptions_lock and self._subscription_mid_lock:
for topic, qos in self._subscriptions.items():
self.subscribe(topic, qos=qos)

def _on_message_handler(self, _, __, message):
self._queue.put(
Expand All @@ -131,23 +140,26 @@ def _on_subscribe_handler(self, _, __, mid, ___):
# we want to know the mid → topic mapping here
# since we want to publish an event with the topic
# that has been subscribed to.
if mid in self._subscription_mid:
self._queue.put(
Event(
MQTT_SUBSCRIBED,
**{MQTT_EVENT_TOPIC: self._subscription_mid.pop(mid)},

with self._subscriptions_lock and self._subscription_mid_lock:
if mid in self._subscription_mid:
self._queue.put(
Event(
MQTT_SUBSCRIBED,
**{MQTT_EVENT_TOPIC: self._subscription_mid.pop(mid)},
)
)
)
else:
logger.error(f"No topic mapping found for subscription {mid}")
else:
logger.error(f"No topic mapping found for subscription {mid}")

def _on_unsubscribe_handler(self, _, __, mid):
# See comment (B), same applies here.
if mid in self._unsubscription_mid:
topic = self._unsubscription_mid.pop(mid)
self._queue.put(Event(MQTT_UNSUBSCRIBED, **{MQTT_EVENT_TOPIC: topic}))
else:
logger.error(f"No topic mapping found for unsubscription {mid}")
with self._subscriptions_lock and self._unsubscription_mid_lock:
if mid in self._unsubscription_mid:
topic = self._unsubscription_mid.pop(mid)
self._queue.put(Event(MQTT_UNSUBSCRIBED, **{MQTT_EVENT_TOPIC: topic}))
else:
logger.error(f"No topic mapping found for unsubscription {mid}")

def _send_subscribe(self, dup, topics, mid=None):
""" See Paho's _send_subscribe, allow for passing a mid. """
Expand Down