Servicestack-RabbitMq: Return response type in message headers - servicestack

Question

Is there any way to add the type of the response dto to the rabbitmq response message's headers collection?
(My consumer is using spring's rabbitmq handler which seems to depend on explicit type information inside the mq header when deserializing.)
Currently servicestack's mq producer already returns serveral headers, such as "content_type='application/json".
I am in need of an additional header, e.g. "typeId"="HelloResponse", so that the consuming web app knows how to deserialize the message, even in RPC cases where the response queue name is some kind of GUID.
Is there some kind of configuration which would enable me to archieve such an behaviour? Or some hook before the message gets published so that I can add the header myself?

Answer 1

I've added support for automatically populating the Message Body Type in RabbitMQ's IBasicProperties.Type as well as adding support for both Publish and GetMessage Filters in this commit.
Here's an example of configuring a RabbitMqServer with custom handlers where you can modify the message and its metadata properties when its published and received:
string receivedMsgApp = null;
string receivedMsgType = null;
var mqServer = new RabbitMqServer("localhost")
{
PublishMessageFilter = (queueName, properties, msg) => {
properties.AppId = "app:{0}".Fmt(queueName);
},
GetMessageFilter = (queueName, basicMsg) => {
var props = basicMsg.BasicProperties;
receivedMsgType = props.Type; //automatically added by RabbitMqProducer
receivedMsgApp = props.AppId;
}
};
mqServer.RegisterHandler<Hello>(m =>
new HelloResponse { Result = "Hello, {0}!".Fmt(m.GetBody().Name) });
mqServer.Start();
Once Configured any message published or received will go through the above handlers, e.g:
using (var mqClient = mqServer.CreateMessageQueueClient())
{
mqClient.Publish(new Hello { Name = "Bugs Bunny" });
}
receivedMsgApp.Print(); // app:mq:Hello.In
receivedMsgType.Print(); // Hello
using (IConnection connection = mqServer.ConnectionFactory.CreateConnection())
using (IModel channel = connection.CreateModel())
{
var queueName = QueueNames<HelloResponse>.In;
channel.RegisterQueue(queueName);
var basicMsg = channel.BasicGet(queueName, noAck: true);
var props = basicMsg.BasicProperties;
props.Type.Print(); // HelloResponse
props.AppId.Print(); // app:mq:HelloResponse.Inq
var msg = basicMsg.ToMessage<HelloResponse>();
msg.GetBody().Result.Print(); // Hello, Bugs Bunny!
}
This change is available from ServiceStack v4.0.33+ that's now available on MyGet.