Adding Exception Message Header to Envelope when moved to error queue

[MatthijsVollenbroek]

Hey everyone,

I am new to using Wolverine and I am trying to connect my micro-service (C# .NET) to an existing RabbitMQ service.
Per convention of the existing services, I want to add a header "x-exception" with the exception message to the header of the envelope. This way, we can see the exception message that caused the message to be moved to the error queue.

I have this configuration

options.Policies
                .OnAnyException()
                .RetryWithCooldown(1.Seconds(), 10.Seconds())
                .Then
                .MoveToErrorQueue()
                .And((_, context, ex) =>
                {
                    context.Envelope!.Headers["x-exception"] = ex.Message;
                    return ValueTask.CompletedTask;
                });    

Everything seems to work, the retries are performed and then in the end after the failed retries the message is moved to the error queue.
However, when I check the message in the error queue. I am not seeing the x-exception header added.
What am I doing wrong here? I have not been able to find any solutions online.

Your help would be greatly appreciated.

With kind regards,

Matthijs

[MatthijsVollenbroek]

I changed it to this

public sealed class RabbitMqMessageErrorHandlingPolicy(IEnumerable<Type> messageTypes) : IHandlerPolicy
{
    public void Apply(IReadOnlyList<HandlerChain> chains, GenerationRules rules, IServiceContainer container)
    {
        var matchingChains = chains
            .Where(x => messageTypes.Contains(x.MessageType));

        foreach (var chain in matchingChains)
        {
            chain.OnAnyException()
                .RetryWithCooldown(1.Seconds(), 10.Seconds())
                .Then
                .CustomAction(this.HandleExceptionMessage, "Moves message to error queue with exception", InvokeResult.Stop);
        }
    }

    private async ValueTask HandleExceptionMessage(IWolverineRuntime runtime, IEnvelopeLifecycle context,
        Exception exception)
    {
        context.Envelope!.Headers.Add("x-exception", exception.Message);
        await context.MoveToDeadLetterQueueAsync(exception);
    }
}

Because i thought maybe the message is not yet loaded.
I do use UseMassTransitInterop, could that have something to do with it? That it removes headers?

[jeremydmiller]

The context.Envelope probably isn't the same envelope in this case. You could just use the database backed DLQ in Wolverine and get all this information. I realize what you're doing is the "MT way", but it's not something we've ever directly supported in Wolverine. It's come up before, but most folks use the database backed DLQ w/ Wolverine

[MatthijsVollenbroek]

Hey Jeremy,

Since database backed DLQ is not an option for me for now, I am trying to find a workaround to make it work.
I now have this

public void Apply(IReadOnlyList<HandlerChain> chains, GenerationRules rules, IServiceContainer container)
    {
        var matchingChains = chains
            .Where(x => messageTypes.Contains(x.MessageType));

        foreach (var chain in matchingChains)
        {
            chain.OnAnyException()
                .RetryWithCooldown(1.Seconds(), 1.Seconds())
                .Then
                .CompensatingAction<object>((message, ex, bus) =>
                {
                    message.WithDeliveryOptions(new DeliveryOptions().WithHeader("x-exception", ex.Message));
                    return ValueTask.CompletedTask;
                }, InvokeResult.Stop)
                .Then.MoveToErrorQueue();
        }
    }

But I expect it to move to the error queue.
But now, the message is not moved at all and stays in the queue as Unacked.

I am not completely following what MoveToErrorQueue does, or what invokeresult does when I check out the source code.
Is there no way right now to add a header to the envelope in some kind of way before moving to error queue?

[jeremydmiller]

Hey man, this isn't something that has ever come up before, so no. Happy to take pull requests, or I might try to do something for native DLQ support as part of V5. You can of course expedite this by becoming a JasperFx client because that's where my priorities have to be this week and next