From 928bb3667a480bdc2ed86dc4132749e591b047e7 Mon Sep 17 00:00:00 2001
From: Fabio Manganiello <info@fabiomanganiello.com>
Date: Mon, 22 Mar 2021 01:51:49 +0100
Subject: [PATCH] Reconnection logic for MQTT disconnections caused by
 temporary errors

---
 platypush/backend/mqtt.py | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/platypush/backend/mqtt.py b/platypush/backend/mqtt.py
index 1091ff7da3..427d7e554a 100644
--- a/platypush/backend/mqtt.py
+++ b/platypush/backend/mqtt.py
@@ -1,6 +1,8 @@
 import json
+import logging
 import os
 import threading
+import time
 from typing import Optional, List, Callable
 
 import paho.mqtt.client as mqtt
@@ -16,6 +18,8 @@ from platypush.utils import set_thread_name
 
 
 class MqttClient(mqtt.Client, threading.Thread):
+    _reconnect_timeout = 10.0
+
     def __init__(self, *args, host: str, port: int, topics: Optional[List[str]] = None,
                  on_message: Optional[Callable] = None, username: Optional[str] = None, password: Optional[str] = None,
                  client_id: Optional[str] = None, tls_cafile: Optional[str] = None, tls_certfile: Optional[str] = None,
@@ -29,6 +33,8 @@ class MqttClient(mqtt.Client, threading.Thread):
         self.topics = set(topics or [])
         self.keepalive = keepalive
         self.on_connect = self.connect_hndl()
+        self.on_disconnect = self.disconnect_hndl()
+        self.logger = logging.getLogger(__name__)
 
         if on_message:
             self.on_message = on_message
@@ -73,6 +79,20 @@ class MqttClient(mqtt.Client, threading.Thread):
 
         return handler
 
+    def disconnect_hndl(self):
+        # noinspection PyUnusedLocal
+        def handler(client, userdata, rc):
+            if not self._stop_scheduled and rc in {mqtt.MQTT_ERR_INVAL, mqtt.MQTT_ERR_AGAIN, mqtt.MQTT_ERR_CONN_LOST,
+                                                   mqtt.MQTT_ERR_CONN_REFUSED, mqtt.MQTT_ERR_NOMEM, mqtt.MQTT_ERR_ERRNO,
+                                                   mqtt.MQTT_ERR_NO_CONN, mqtt.MQTT_ERR_PAYLOAD_SIZE,
+                                                   mqtt.MQTT_ERR_QUEUE_SIZE, mqtt.MQTT_ERR_UNKNOWN}:
+                self.logger.warning('Unexpected disconnection from {}:{}. MQTT error: {}'.format(
+                    self.host, self.port, rc))
+                time.sleep(self._reconnect_timeout)
+                self.connect(host=self.host, port=self.port, keepalive=self.keepalive)
+
+        return handler
+
     def run(self):
         super().run()
         self.connect(host=self.host, port=self.port, keepalive=self.keepalive)