Queue, Topic, and Binding Management

TIP

Wolverine assumes that exchanges should be "fanout" unless explicitly configured otherwise

Reusing a code sample from up above, the AutoProvision() declaration will direct Wolverine to create any missing Rabbit MQ exchanges, queues, or bindings declared in the application configuration at application bootstrapping time.

using var host = await Host.CreateDefaultBuilder()
    .UseWolverine(opts =>
    {
        opts.UseRabbitMq(rabbit => { rabbit.HostName = "localhost"; })
            // I'm declaring an exchange, a queue, and the binding
            // key that we're referencing below.
            // This is NOT MANDATORY, but rather just allows Wolverine to
            // control the Rabbit MQ object lifecycle
            .DeclareExchange("exchange1", ex => { ex.BindQueue("queue1", "key1"); })

            // This will direct Wolverine to create any missing Rabbit MQ exchanges,
            // queues, or binding keys declared in the application at application
            // start up time
            .AutoProvision();

        opts.PublishAllMessages().ToRabbitExchange("exchange1");
    }).StartAsync();

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At development time -- or occasionally in production systems -- you may want to have the messaging queues purged of any old messages at application startup time. Wolverine supports that with Rabbit MQ using the AutoPurgeOnStartup() declaration:

using var host = await Host.CreateDefaultBuilder()
    .UseWolverine(opts =>
    {
        opts.UseRabbitMq()
            .AutoPurgeOnStartup();
    }).StartAsync();

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Or you can be more selective and only have certain queues of volatile messages purged at startup as shown below:

using var host = await Host.CreateDefaultBuilder()
    .UseWolverine(opts =>
    {
        opts.UseRabbitMq()
            .DeclareQueue("queue1")
            .DeclareQueue("queue2", q => q.PurgeOnStartup = true);
    }).StartAsync();

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Wolverine's Rabbit MQ integration also supports the Oakton stateful resource model, so you can make a generic declaration to auto-provision the Rabbit MQ objects at startup time (as well as any other stateful Wolverine resources like envelope storage) with the Oakton declarations as shown in the setup below that uses the AddResourceSetupOnStartup() declaration:

var builder = WebApplication.CreateBuilder(args);

builder.Host.ApplyOaktonExtensions();

builder.Host.UseWolverine(opts =>
{
    // I'm setting this up to publish to the same process
    // just to see things work
    opts.PublishAllMessages()
        .ToRabbitExchange("issue_events", exchange => exchange.BindQueue("issue_events"))
        .UseDurableOutbox();

    opts.ListenToRabbitQueue("issue_events").UseDurableInbox();

    opts.UseRabbitMq(factory =>
    {
        // Just connecting with defaults, but showing
        // how you *could* customize the connection to Rabbit MQ
        factory.HostName = "localhost";
        factory.Port = 5672;
    });
});

// This is actually important, this directs
// the app to build out all declared Postgresql and
// Rabbit MQ objects on start up if they do not already
// exist
builder.Services.AddResourceSetupOnStartup();

// Just pumping out a bunch of messages so we can see
// statistics
builder.Services.AddHostedService<Worker>();

builder.Services.AddMarten(opts =>
{
    // I think you would most likely pull the connection string from
    // configuration like this:
    // var martenConnectionString = builder.Configuration.GetConnectionString("marten");
    // opts.Connection(martenConnectionString);

    opts.Connection(Servers.PostgresConnectionString);
    opts.DatabaseSchemaName = "issues";

    // Just letting Marten know there's a document type
    // so we can see the tables and functions created on startup
    opts.RegisterDocumentType<Issue>();

    // I'm putting the inbox/outbox tables into a separate "issue_service" schema
}).IntegrateWithWolverine(x => x.MessageStorageSchemaName = "issue_service");

var app = builder.Build();

app.MapGet("/", () => "Hello World!");

// Actually important to return the exit code here!
return await app.RunOaktonCommands(args);

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Note that this stateful resource model is also available at the command line as well for deploy time management.

Runtime Declaration

From a user request, there are some extension methods in the WolverineFx.RabbitMQ Nuget off of IWolverineRuntime that will enable you to first declare new exchanges, queues, and bindings at runtime, and also enable you to "unbind" a queue from an exchange. That syntax is shown below:

// _host is an IHost
var runtime = _host.Services.GetRequiredService<IWolverineRuntime>();

// Declare new Exchanges, Queues, and Bindings at runtime
runtime.ModifyRabbitMqObjects(o =>
{
    var queue = o.DeclareQueue(queueName);
    var exchange = o.DeclareExchange(exchangeName);
    queue.BindExchange(exchange.ExchangeName, bindingKey);
});

// Unbind a queue from an exchange
runtime.UnBindRabbitMqQueue(queueName, exchangeName, bindingKey);

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Inside of Wolverine Extensions

If you need to declare Rabbit MQ queues, exchanges, or bindings within a Wolverine extension, you can quickly access and make additions to the Rabbit MQ integration with your Wolverine application like so:

public class MyModuleExtension : IWolverineExtension
{
    public void Configure(WolverineOptions options)
    {
        options.ConfigureRabbitMq()
            // Make any Rabbit Mq configuration or declare
            // additional Rabbit Mq options through the normal
            // syntax
            .DeclareExchange("my-module")
            .DeclareQueue("my-queue");
    }
}

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