Don't retry when MQTT response is unauthorized

Author: justmobilize

adafruit_minimqtt/adafruit_minimqtt.py

@@ -72,12 +72,18 @@
 MQTT_PKT_TYPE_MASK = const(0xF0)
 
 
+CONNACK_ERROR_INCORRECT_PROTOCOL = const(0x01)
+CONNACK_ERROR_ID_REJECTED = const(0x02)
+CONNACK_ERROR_SERVER_UNAVAILABLE = const(0x03)
+CONNACK_ERROR_INCORECT_USERNAME_PASSWORD = const(0x04)
+CONNACK_ERROR_UNAUTHORIZED = const(0x05)
+
 CONNACK_ERRORS = {
-    const(0x01): "Connection Refused - Incorrect Protocol Version",
-    const(0x02): "Connection Refused - ID Rejected",
-    const(0x03): "Connection Refused - Server unavailable",
-    const(0x04): "Connection Refused - Incorrect username/password",
-    const(0x05): "Connection Refused - Unauthorized",
+    CONNACK_ERROR_INCORRECT_PROTOCOL: "Connection Refused - Incorrect Protocol Version",
+    CONNACK_ERROR_ID_REJECTED: "Connection Refused - ID Rejected",
+    CONNACK_ERROR_SERVER_UNAVAILABLE: "Connection Refused - Server unavailable",
+    CONNACK_ERROR_INCORECT_USERNAME_PASSWORD: "Connection Refused - Incorrect username/password",
+    CONNACK_ERROR_UNAUTHORIZED: "Connection Refused - Unauthorized",
 }
 
 _default_sock = None  # pylint: disable=invalid-name
@@ -87,6 +93,10 @@
 class MMQTTException(Exception):
     """MiniMQTT Exception class."""
 
+    def __init__(self, error, code=None):
+        super().__init__(error, code)
+        self.code = code
+
 
 class NullLogger:
     """Fake logger class that does not do anything"""
@@ -428,8 +438,14 @@ def connect(
                 self.logger.warning(f"Socket error when connecting: {e}")
                 backoff = False
             except MMQTTException as e:
-                last_exception = e
                 self.logger.info(f"MMQT error: {e}")
+                if e.code in [
+                    CONNACK_ERROR_INCORECT_USERNAME_PASSWORD,
+                    CONNACK_ERROR_UNAUTHORIZED,
+                ]:
+                    # No sense trying these again, re-raise
+                    raise
+                last_exception = e
                 backoff = True
 
         if self._reconnect_attempts_max > 1:
@@ -535,7 +551,7 @@ def _connect(
                 rc = self._sock_exact_recv(3)
                 assert rc[0] == 0x02
                 if rc[2] != 0x00:
-                    raise MMQTTException(CONNACK_ERRORS[rc[2]])
+                    raise MMQTTException(CONNACK_ERRORS[rc[2]], code=rc[2])
                 self._is_connected = True
                 result = rc[0] & 1
                 if self.on_connect is not None:

tests/test_backoff.py

@@ -18,18 +18,24 @@ class TestExpBackOff:
     """basic exponential back-off test"""
 
     connect_times = []
+    raise_exception = None
 
     # pylint: disable=unused-argument
     def fake_connect(self, arg):
         """connect() replacement that records the call times and always raises OSError"""
         self.connect_times.append(time.monotonic())
-        raise OSError("this connect failed")
+        raise self.raise_exception
 
     def test_failing_connect(self) -> None:
         """test that exponential back-off is used when connect() always raises OSError"""
         # use RFC 1918 address to avoid dealing with IPv6 in the call list below
         host = "172.40.0.3"
         port = 1883
+        self.connect_times = []
+        error_code = MQTT.CONNACK_ERROR_SERVER_UNAVAILABLE
+        self.raise_exception = MQTT.MMQTTException(
+            MQTT.CONNACK_ERRORS[error_code], code=error_code
+        )
 
         with patch.object(socket.socket, "connect") as mock_method:
             mock_method.side_effect = self.fake_connect
@@ -54,3 +60,33 @@ def test_failing_connect(self) -> None:
             print(f"connect() call times: {self.connect_times}")
             for i in range(1, connect_retries):
                 assert self.connect_times[i] >= 2**i
+
+    def test_unauthorized(self) -> None:
+        """test that exponential back-off is used when connect() always raises OSError"""
+        # use RFC 1918 address to avoid dealing with IPv6 in the call list below
+        host = "172.40.0.3"
+        port = 1883
+        self.connect_times = []
+        error_code = MQTT.CONNACK_ERROR_UNAUTHORIZED
+        self.raise_exception = MQTT.MMQTTException(
+            MQTT.CONNACK_ERRORS[error_code], code=error_code
+        )
+
+        with patch.object(socket.socket, "connect") as mock_method:
+            mock_method.side_effect = self.fake_connect
+
+            connect_retries = 3
+            mqtt_client = MQTT.MQTT(
+                broker=host,
+                port=port,
+                socket_pool=socket,
+                ssl_context=ssl.create_default_context(),
+                connect_retries=connect_retries,
+            )
+            print("connecting")
+            with pytest.raises(MQTT.MMQTTException) as context:
+                mqtt_client.connect()
+            assert "Connection Refused - Unauthorized" in str(context)
+
+            mock_method.assert_called()
+            assert len(self.connect_times) == 1