Failure to detect MQTT service on boot

[kb2ma]

I consistently see this error after a boot/reboot:

Error looking for MQTT service: HTTPConnectionPool(host='10.114.104.1', port=48484): Max retries exceeded with url: /v2/applications/state?apikey=d530c94d742e47c3895754d6e777786d (Caused by NewConnectionError('<urllib3.connection.HTTPConnection object at 0x7fb02a9700>: Failed to establish a new connection: [Errno 111]

The sensor service does not terminate on this error. Instead, the mqtt_detect() function that makes the HTTP request just returns false. If I later restart the sensor service, the error does not occur. So, somehow then the system is not ready for this request. Does it make sense to add a retry over several seconds? See 70ace12 for example.

This failure is serious for another service that depends on receiving sensor messages. As a workaround, I manually set the MQTT_ADDRESS environment variable to 'mqtt', and the sensor service sends the expected messages.