How to post a command in Rabbit MQ that uses a Header Exchange with parameters?

[leonErhard]

I was reading the docs about how to configure and post commands with External Brokers like RabbitMQ, but I notice there's no content about how to configure and send messages in an Header Exchange that has parameters to use the correct queue. How can I Post a command in a Header Exchange with parameters ?

[DevJonny]

Hi @leonErhard.

You can configure Brighter to use the Headers exchange when you setup the RmqMessagingGatewayConnection, so using the example in the RMQ configuration section of docs. So when you create the Exchange object you can pass ExchangeType.Headers in the type parameter.

public void ConfigureServices(IServiceCollection services)
{
    services.AddBrighter(...)
        .UseExternalBus(new RmqProducerRegistryFactory(
                    new RmqMessagingGatewayConnection
                    {
                        Name = "MyCommandConnection",
                        AmpqUri = new AmqpUriSpecification(
                            new Uri("amqp://guest:guest@localhost:5672")
                            connectionRetryCount: 5,
                            retryWaitInMilliseconds: 250,
                            circuitBreakerTimeInMilliseconds = 30000
                        ),
                        Exchange = new Exchange("paramore.brighter.exchange", type: ExchangeType.Headers, durable: true, supportDelay: true),
                        DeadLetterExchange = new Exchange("paramore.brighter.exchange.dlq", durable: true, supportDelay: false),
                        Heartbeat = 15,
                        PersistMessages = true
                    },
            ... //publication, see below
        ).Create()
}

Hope this helps!

[leonErhard]

Thanks! How can i Post a command with a header parameter "mail":true ?

[DevJonny]

Sorry for the slow reply @leonErhard it completely slipped my mind. Adding a header to the RMQ message can be done when creating your Message Mappers. All you need to do, besides the aforementioned code, is add something along the lines of

...
header.Bag.TryAdd("mail", true);
...

So when Brighter serialises your Command/Event into a RMQ message, all the items in the Bag dictionary of the message are added as headers to the message.