What is the intended MassTransit middleware construct for setting mult-tenant scope values upon each message received?

Question

I'm using MassTransit with Autofac and need a way to interrogate inbound messages for a tenant Id which will be used to dynamically construct a connection string. So the logical steps would be as follows:

1. A message is received

2. The tenant Id is retrieved from the message and a per-message-scoped component is used to set the tenant Id

3. A message consumer is resolved by the container which uses the per-message-scoped component to construct dependencies accordingly.

   MassTransit has an example of how to create message filters here. At first glance this seems like a potential solution, but it doesn't appear that a new instance of a message filter is resolved using the same lifetime scope as is used to resolve the consumer for each message.

So my question is this: Can message filters be used for this purpose? If so, please provide an example or point to an example showing something similar (e.g. Anything where a DI-container is used which supports scopes for accessing per-message lifetime resources). If not, what if any is the intended way of facilitating this need with MassTransit?

Answer 1

Based on looking at the code, you should be able to create a new ILifetimeScope at the ConsumeContext level, and it will be used by the consumer. An example of the filter logic is included below.

public class LifetimeScopeFilter :
    IFilter<ConsumeContext>
{
    LifetimeScopeFilter(ILifetimeScope mainScope)
    {
        _mainScope = mainScope;
    }

    public void Probe(ProbeContext context)
    {
        var scope = context.CreateFilterScope("lifetimeScope");
    }

    public async Task Send(ConsumeContext context, IPipe<ConsumeContext> next)
    {
        ILifetimeScope scope = null;

        try
        {
            context.GetOrAddPayload<ILifetimeScope>(() => scope = _mainScope.BeginLifetimeScope())

            await next.Send(context).ConfigureAwait(false);
        }
        finally
        {
            scope?.Dispose();
        }
    }
}