MQTT sparkplug v1.0 to EventGrid how to decode data when forwarding to an EventHub.

Question

MQTT sparkplug v1.0 to EventGrid how to decode data when forwarding to an EventHub.

Karl Fredrik Wirgenes 0

I am sending sparkplug B MQTT into an Azure eventgrid. The data is then sent to an eventhub using topics.

My problem is that in the eventhub the data format is a Base64 payload decoded according to the sparkplug B protocol. Preferably i want the data decoded before it reaches the eventhub. How can I achieve this using azure services?

AdamWoodland-0640 0 Reputation points

2025-11-19T03:55:54.77+00:00

From https://learn.microsoft.com/en-us/azure/event-grid/sparkplug-support

"Native support for binary Sparkplug payloads over secure Transport Layer Security (TLS)"

Can you confirm if "native support" means that Event Grid itself can automatically decode the protobuf into its JSON similar to how various MQTT clients can? If not, what exactly does "native support" refer to?

Without automatic protobuf decoding we're still being knee-capped by having to decode somewhere down the line
Siddhesh Desai 650 Reputation points Microsoft External Staff Moderator

2025-11-19T11:16:36+00:00
Hi Karl Fredrik Wirgenes,

Thanks for reaching out on Microsoft Q&A.

Event Grid’s Sparkplug “native support” is protocol-level (topic namespace, QoS 1, retain/LWT, TLS, routing) and not a payload conversion. the binary Protobuf payload is delivered as it is.

Event Grid MQTT broker supports Sparkplug B protocol natively, which means:

It can accept Sparkplug-compliant MQTT messages over TLS without requiring custom adapters.

It understands Sparkplug topic namespace and session semantics for routing and filtering.

The payload (binary protobuf) is transported as it is. Event Grid does not decode it into any format, eg. json.

Refer the answer here: https://learn.microsoft.com/en-us/answers/questions/2244864/mqtt-messaged-displayed-in-event-hub-data-explorer > Which suggests using Azure Functions to decode the Base64 payload into readable format in Event hub/Event Grid.

You can follow below approach:

You can create a Function with Event Grid Trigger and trigger it as soon as you receive the base64 payload from Event Grid > Decode its raw bytes > Parse using Sparkplug’s Protobuf schema > Return Json to Event Hub. In order to parse the protobuf schema in your function refer this thread: https://stackoverflow.com/questions/76962110/where-are-the-sparkplug-b-pb2-payload-methods-in-a-protobuf-object

You can also use Logic app connector which triggers when a payload is received in Event Grid > Call Azure Function that decoded it > Push the decoded content to Event Hub.

1 answer

Your answer

AdamWoodland-0640 0 Reputation points

2025-11-19T03:55:54.77+00:00

From https://learn.microsoft.com/en-us/azure/event-grid/sparkplug-support

"Native support for binary Sparkplug payloads over secure Transport Layer Security (TLS)"

Can you confirm if "native support" means that Event Grid itself can automatically decode the protobuf into its JSON similar to how various MQTT clients can? If not, what exactly does "native support" refer to?

Without automatic protobuf decoding we're still being knee-capped by having to decode somewhere down the line
Siddhesh Desai 650 Reputation points Microsoft External Staff Moderator

2025-11-19T11:16:36+00:00

Hi Karl Fredrik Wirgenes,

Thanks for reaching out on Microsoft Q&A.

Event Grid’s Sparkplug “native support” is protocol-level (topic namespace, QoS 1, retain/LWT, TLS, routing) and not a payload conversion. the binary Protobuf payload is delivered as it is.

Event Grid MQTT broker supports Sparkplug B protocol natively, which means:

It can accept Sparkplug-compliant MQTT messages over TLS without requiring custom adapters.

It understands Sparkplug topic namespace and session semantics for routing and filtering.

The payload (binary protobuf) is transported as it is. Event Grid does not decode it into any format, eg. json.

Refer the answer here: https://learn.microsoft.com/en-us/answers/questions/2244864/mqtt-messaged-displayed-in-event-hub-data-explorer > Which suggests using Azure Functions to decode the Base64 payload into readable format in Event hub/Event Grid.

You can follow below approach:

You can create a Function with Event Grid Trigger and trigger it as soon as you receive the base64 payload from Event Grid > Decode its raw bytes > Parse using Sparkplug’s Protobuf schema > Return Json to Event Hub. In order to parse the protobuf schema in your function refer this thread: https://stackoverflow.com/questions/76962110/where-are-the-sparkplug-b-pb2-payload-methods-in-a-protobuf-object

You can also use Logic app connector which triggers when a payload is received in Event Grid > Call Azure Function that decoded it > Push the decoded content to Event Hub.

Answer 1

Hi Karl Fredrik Wirgenes,

Thanks for reaching out on Microsoft Q&A

Use Azure Functions or Azure Stream Analytics to decode Sparkplug B protobuf payloads after Event Grid ingestion but before forwarding to Event Hub

Azure Event Grid subscription triggers an Azure Function

· The Event Grid receives Sparkplug B MQTT messages (still base64 protobuf encoded).

· The Azure Function is triggered by the Event Grid event.

Azure Function decodes the Sparkplug B protobuf payload

· Use a Sparkplug B protobuf .proto definition and Google Protobuf library to decode the base64 payload into JSON or structured data.

· This converts binary protobuf payloads to readable JSON before any further processing.

Azure Function publishes the decoded data to Azure Event Hub

· The decoded JSON or clean data is sent to Event Hub.

· Downstream systems consuming Event Hub receive decoded, readable data.

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