Request Reply

Request-reply is one of the basic messaging patterns. From a high level, a request-reply scenario involves an application that sends a message (the request) and expects to receive a message in return (the reply).

Implementing request-reply with ArtemisNetClient

Implementing this style of system architecture is really easy with ArtemisNetClient.

Request side

From the request side, all you need to do is create an instance of IRequestReplyClient interface. IRequestReplyClient is responsible for sending messages and listening to responses asynchronously.

var connectionFactory = new ConnectionFactory();
var endpoint = Endpoint.Create("localhost", 5672, "guest", "guest");
var connection = await connectionFactory.CreateAsync(endpoint);
await using var requestReplyClient = await connection.CreateRequestReplyClientAsync();
var response = await requestReplyClient.SendAsync("my-address", RoutingType.Anycast, new Message("foo"), default);
var test = response.GetBody<string>(); // bar

Response side

All the messages sent by IRequestReplyClient have a couple of important properties set:

• ReplyTo is the address where the reply message is expected to be delivered.
• CorrelationId is the unique identifier that is used by IRequestReplyClient to correlate requests with responses. You may have multiple outstanding requests, so it's crucial to set this property on the response message.

var connectionFactory = new ConnectionFactory();
var endpoint = Endpoint.Create("localhost", 5672, "guest", "guest");
var connection = await connectionFactory.CreateAsync(endpoint);
await using var consumer = await connection.CreateConsumerAsync("my-address", RoutingType.Anycast);
var request = await consumer.ReceiveAsync();
await using var producer = await connection1.CreateAnonymousProducerAsync();
await producer.SendAsync(request.ReplyTo, new Message("bar")
{
    CorrelationId = request.CorrelationId
});
await consumer.AcceptAsync(request);

Implementing request-reply with ArtemisNetClient.Extensions.DependencyInjection

Request side

DependencyInjection package provides a simple way of registering IRequestReplyClient in a DI container.

public void ConfigureServices(IServiceCollection services)
{
    /*...*/ 
    var endpoints = new[] { Endpoint.Create(host: "localhost", port: 5672, "guest", "guest") };
    services.AddActiveMq("bookstore-cluster", endpoints)
            .AddRequestReplyClient<MyRequestReplyClient>();
    /*...*/
}

MyRequestReplyClient is your custom class that expects the IRequestReplyClient to be injected via the constructor. Once you have your custom class, you can either expose the IRequestReplyClient directly or encapsulate sending logic inside of it:

public class MyRequestReplyClient
{
    private readonly IRequestReplyClient _requestReplyClient;
    public MyRequestReplyClient(IRequestReplyClient requestReplyClient)
    {
        _requestReplyClient = requestReplyClient;
    }

    public async Task<TResponse> SendAsync<TRequest, TResponse>(TRequest request, CancellationToken cancellationToken)
    {
        var serialized = JsonSerializer.Serialize(request);
        var address = typeof(TRequest).Name;
        var msg = new Message(serialized);
        var response = await _requestReplyClient.SendAsync(address, msg, cancellationToken);
        return JsonSerializer.Deserialize<TResponse>(response.GetBody<string>());
    }
}

Response side

TODO