Persist headers when redelivering a RabbitMq message using MassTransit

Question

Purpose: I need to keep track of headers when I redeliver a message.

Configuration:

• RabbitMQ 3.7.9
• Erlang 21.2
• MassTransit 5.1.5
• MySql 8.0 for the Quartz database

What I've tried without success:

first attempt:

await context.Redeliver(TimeSpan.FromSeconds(5), (consumeCtx, sendCtx) => {
   if (consumeCtx.Headers.TryGetHeader("SenderApp", out object sender))
   {
      sendCtx.Headers.Set("SenderApp", sender);
   }
}).ConfigureAwait(false);

second attempt:

protected Task ScheduleSend(Uri rabbitUri, double delay)
{
  return GetBus().ScheduleSend<IProcessOrganisationUpdate>(
    rabbitUri,
    TimeSpan.FromSeconds(delay),
    _Data,
    new HeaderPipe(_SenderApp, 0));
}

public class HeaderPipe : IPipe<SendContext>
{
  private readonly byte   _Priority;
  private readonly string _SenderApp;

  public HeaderPipe (byte priority)
  {
    _Priority  = priority;
    _SenderApp = Assembly.GetEntryAssembly()?.GetName()?.Name ?? "Default";
  }

  public HeaderPipe (string senderApp, byte priority)
  {
    _Priority  = priority;
    _SenderApp = senderApp;
  }

  public void Probe (ProbeContext context)
  { }

  public Task Send (SendContext context)
  {
    context.Headers.Set("SenderApp", _SenderApp);
    context.SetPriority(_Priority);
    return Task.CompletedTask;
  }
}

Expected: FinQuest.Robot.DBProcess

Result: null

I log in Consume method my SenderApp. The first time it's look like this

Initial trigger checking returns true for FinQuest.Robots.OrganisationLinkedinFeed (id: 001ae487-ad3d-4619-8d34-367881ec91ba, sender: FinQuest.Robot.DBProcess, modif: LinkedIn)

and looks like this after the redelivery

Initial trigger checking returns true for FinQuest.Robots.OrganisationLinkedinFeed (id: 001ae487-ad3d-4619-8d34-367881ec91ba, sender: , modif: LinkedIn)

What I'm doing wrong ? I don't want to use the Retry feature due to its maximum number of retry (I don't want to be limited).

Thanks in advance.

Answer 1

There is a method, used by the redelivery filter, that you might want to use:

https://github.com/MassTransit/MassTransit/blob/develop/src/MassTransit/SendContextExtensions.cs#L90

public static void TransferConsumeContextHeaders(this SendContext sendContext, ConsumeContext consumeContext)

In your code, you would use it:

await context.Redeliver(TimeSpan.FromSeconds(5), (consumeCtx, sendCtx) => {
    sendCtx.TransferConsumeContextHeaders(consumeCtx);
});