How to register correctly for direct methods in an iot edge java module?

Question

I have an iot edge module in java developed with VS code. Up to now everything was working (meaning: I can send messages to the iot hub without problems). Now I want to add the option to receive messages from the iot hub. As this is not directly implemented, I am subscribing for direct method calls. This is seemingly not working correctly in my case. But, as soon as I remove the subscription to the method, everything works fine. So, the act of subscription seems to break something.

When I add the code to subscribe for direct method calls, the module still can send messages to the iot hub, but the connection gets lost and re-established all the time in 5 second intervals. After some time (about 5 minutes) I see a message from the iotHubEventCallback (ERROR):

230162 [MQTT Rec: myEdgeDevice/JavaModule] WARN HbIIoTGateway - Connection Status: Retrying

230995 [MQTT Rec: myEdgeDevice/JavaModule] WARN HbIIoTGateway - Connection Status: Connected

240196 [MQTT Rec: myEdgeDevice/JavaModule] WARN HbIIoTGateway - Connection Status: Retrying

240994 [MQTT Rec: myEdgeDevice/JavaModule] WARN HbIIoTGateway - Connection Status: Connected

250228 [MQTT Rec: myEdgeDevice/JavaModule] WARN HbIIoTGateway - Connection Status: Retrying

250229 [azure-iot-sdk-IotHubSendTask] INFO HbIIoTGateway - Direct method # IoT Hub responded to device method acknowledgement with status: ERROR

251005 [MQTT Rec: myEdgeDevice/JavaModule] WARN HbIIoTGateway - Connection Status: Connected

After that, the connection remains stable. But, I cannot invoke method calls (e.g. from the azure portal), they get a timeout:

Failed to invoke device method: {"message":"GatewayTimeout:{\r\n \"Message\": \"{\\"errorCode\\":504101,\\"trackingId\\":\\"3558e6feadd54b5c9f248bdbf20bd5e0-G:19-TimeStamp:04/26/2019 05:20:00\\",\\"message\\":\\"Timed out waiting for the response from device.\\",\\"info\\":{\\"timeout\\":\\"00:00:10\\"},\\"timestampUtc\\":\\"2019-04-26T05:20:00.6977425Z\\"}\",\r\n \"ExceptionMessage\": \"\"\r\n}"}

The status of the iotedge service seems unproblematic:

Apr 26 05:21:09 peers_docker_dev iotedged[52836]: 2019-04-26T05:21:09Z [INFO] - Checking edge runtime status

Apr 26 05:21:09 peers_docker_dev iotedged[52836]: 2019-04-26T05:21:09Z [INFO] - Edge runtime is running.

Apr 26 05:21:10 peers_docker_dev iotedged[52836]: 2019-04-26T05:21:10Z [INFO] - [mgmt] - - - [2019-04-26 05:21:10.206275755 UTC] "GET /modules?api-version=2018-06-28 HTTP/1.1" 200 OK 1483 "-" "-" pid(52

This is the code in question:

            m_client = new ModuleClient(sConnString, IotHubClientProtocol.MQTT);

            // Set the callback for messages 
            m_client.setMessageCallback(INPUT_NAME, new MessageCallback()
            {
                public IotHubMessageResult execute(Message msg, Object context)
                {
                    App.m_logger.info("Received message from hub: " + new String(msg.getBytes(), Message.DEFAULT_IOTHUB_MESSAGE_CHARSET));

                    return IotHubMessageResult.COMPLETE;
                }
            }, m_client);

            // Register the callback for connection state change
            m_client.registerConnectionStatusChangeCallback(new IotHubConnectionStatusChangeCallback ()
            {
                public void execute(IotHubConnectionStatus status, IotHubConnectionStatusChangeReason statusChangeReason, Throwable throwable, Object callbackContext) 
                {
                    String statusStr = "Connection Status: %s";
                    switch (status) 
                    {
                    case CONNECTED:
                        App.m_logger.warn(String.format(statusStr, "Connected"));
                        break;
                    case DISCONNECTED:
                        App.m_logger.error(String.format(statusStr, "Disconnected"));
                        if (throwable != null) 
                        {
                            throwable.printStackTrace();
                        }
                        break;
                    case DISCONNECTED_RETRYING:
                        App.m_logger.warn(String.format(statusStr, "Retrying"));
                        break;
                    default:
                        break;
                    }
                }
            }, null);
            // Open client
            m_client.open();

            // Register to receive direct method calls.
            m_client.subscribeToMethod(new DeviceMethodCallback() {
                @Override
                public DeviceMethodData call(String methodName, Object methodData, Object context) {
                    App.m_logger.info("Method called:" + methodName);
                    return new DeviceMethodData(METHOD_SUCCESS, "Executed direct method " + methodName);
                }
                }, null, new IotHubEventCallback()
                {
                    public void execute(IotHubStatusCode status, Object context) 
                    {
                        App.m_logger.info("Direct method # IoT Hub responded to device method acknowledgement with status: " + status.name());
                    }
                }, null);

The actual output is shown above. I would like to have a stable connection and receive method calls. Any ideas what I might be doing wrong?

Thanks for your help!

PKetterle PKetterle · Accepted Answer · 2019-04-30T11:18:41

Just to close this problem: I could make it work by just adding a new device and inside a new module in the azure portal. With those connection strings it works.

I don't know what I may have done wrong with the first device/module. If you have any ideas, please let me know.

Thanks and best regards,

How to register correctly for direct methods in an iot edge java module?

1 Answers