Message Routing in Azure IoT Hub returning application/octet-stream

Question

I am routing messages from an Azure IoT Hub to a blob container ( Azure Storage as a routing endpoint ). The messages sent to the IoT Hub are of Content Type: 'application/json' and Content Encoding: 'UTF-8'. However, when they arrive in blob storage several of these messages are batched together into one file with Content Type 'application/octet-stream'. Thus, for instance Power BI is not able to read these files in JSON format when reading directly from the blob.

• Is there any way to route these messages so that each single message is saved as a json file in the blob container?

Answer 1

I am routing messages from an Azure IoT Hub to a blob container ( Azure Storage as a routing endpoint ). The messages sent to the IoT Hub are of Content Type: 'application/json' and Content Encoding: 'UTF-8'. However, when they arrive in blob storage several of these messages are batched together into one file with Content Type 'application/octet-stream'. Thus, for instance Power BI is not able to read these files in JSON format when reading directly from the blob.

• Is there any way to route these messages so that each single message is saved as a json file in the blob container?

Answer 2

The message encoding needs to be done by the device stream or as part of a module to translate the protocol. Each protocol (AMQP, MQTT, and HTTP) uses a different method to encode the message from base64 to UTF-8.

To route messages based on message body, you must first add property 'contentType' (ct) to the end of the MQTT topic and set its value to be application/json;charset=utf-8. An example is shown below.

devices/{device-id}/messages/events/$.ct=application%2Fjson%3Bcharset%3Dutf-8

https://learn.microsoft.com/en-us/azure/iot-hub/iot-hub-mqtt-support