Issue with NServiceBus.EnclosedMessageType Header Being Removed on Exception

1

We are consuming events from another team that uses Azure Functions with Azure Service Bus output binding to publish events. However, since these events do not contain the NServiceBus.EnclosedMessageType header, our NServiceBus endpoint does not know which handler the message belongs to.

To resolve this, we implemented a mutator (IMutateIncomingTransportMessages) that manually sets the NServiceBus.EnclosedMessageType header. This allows the message to be processed correctly.

However, we observed an issue:

If an exception occurs in the handler, the NServiceBus.EnclosedMessageType header is removed.
As a result, tools like Service Insight display “unknown” as the MessageType, making debugging difficult.
Question:
Is there any way to ensure that the NServiceBus.EnclosedMessageType header remains unchanged, even after an exception occurs in the handler?

Would appreciate any guidance or best practices to handle this scenario.

2

@Fabian_Trottmann
I’ve reproduced your issue using the AzureServiceBus Native Integration sample and tried the message mutator as you suggested. I could see the message properly deserialized in the handler, but when a failure occurred, the header was not set when passing the message to the error queue.

Next, I tried using behaviors to manipulate the headers
In my case, I added the NServiceBus.EnclosedMessageTypes header based on another header that I added to the sample, this is simply and implementation detail though.

I added a behavior for IIncomingPhysicalMessageContext and one for IRecoverabilityContext

Examples:

class IncomingHeaderBehavior :
    Behavior<IIncomingPhysicalMessageContext>
{
    public override Task Invoke(IIncomingPhysicalMessageContext context, Func<Task> next)
    {
        var headers = context.Message.Headers;
        headers.TryAdd(Headers.EnclosedMessageTypes,headers["X-SomeType"]);
        return next();
    }
}

class RecoverabilityBehavior:
    Behavior<IRecoverabilityContext>
{
    public override Task Invoke(IRecoverabilityContext context, Func<Task> next)
    {
        var headers = context.FailedMessage.Headers;
        headers.TryAdd(Headers.EnclosedMessageTypes,headers["X-SomeType"]);
        return next();
    }
}

then add the behaviors to endpointConfiguraiton

endpointConfiguration.Pipeline.Register(typeof(IncomingHeaderBehavior), "Manipulates incoming headers");

endpointConfiguration.Pipeline.Register(typeof(RecoverabilityBehavior),"manipulates recoverability headers");

The MessageMutator that you are using would likely be sufficient for the incoming messages. Still, you would need something to manipulate them during recoverability to see the correct type in ServicePulse and ServiceInsight.

I hope this helps.

1 Like
3

Hello @adamwright
That works for me, thank you very much!