raise error for subsequent c2d requests

Author: brentru

adafruit_azureiot.py

@@ -79,14 +79,17 @@ def _parse_http_status(status_code, status_reason):
     def get_hub_message(self, device_id):
         """Returns a message from a Microsoft Azure IoT Hub (Cloud-to-Device), or -1
         if the message queue is empty.
-        NOTE: HTTP Cloud-to-Device messages are throttled. Poll every 25 minutes, or more.
+        NOTE: HTTP Cloud-to-Device messages are throttled. Poll every 25+ minutes.
         :param int device_id: Device identifier.
         """
         reject_message = True
         # get a device-bound notification
         path = "{0}/devices/{1}/messages/deviceBound?api-version={2}".format(self._iot_hub_url,
                                                                              device_id, AZ_API_VER)
-        data = self._get(path, is_c2d=True)
+        try:
+            data = self._get(path, is_c2d=True)
+        except RuntimeError:
+            raise RuntimeError('HTTP C2D Messages are HEAVILY throttled, poll every 25 min.')
         if data == 204: # device's message queue is empty
             return -1
         etag = data[1]['etag']

examples/azureiot_simpletest.py

@@ -42,6 +42,8 @@
 print('Data Sent!')
 
 # Receive a Cloud-to-Device message
+# NOTE: HTTP Cloud-to-Device messages are HEAVILY throttled over HTTP.
+# Microsoft suggests a polling interval of the below code for every 25 minutes.
 print('Receiving a message from an Azure IoT Hub...')
 message = hub.get_hub_message(device_id)
 if message == -1: