I am using MassTransit to publish\subscribe messages using RabbitMQ. I want to inject dependencies in dependency in consumers so that consumers can insert data to the database. However, I found the examples in the documentation confusing.
public class MessageConsumer : IConsumer<Message>
{
private IDao dao;
public MessageConsumer(IDao dao)
{
this.dao = dao;
}
public async Task Consume(ConsumeContext<Message> context)
{
Console.WriteLine("Order Submitted: {0}", context.Message.MessageId);
}
}
The bus is configured as follows
static void Main(string[] args)
{
ContainerBuilder builder = new ContainerBuilder();
builder.RegisterType<ConcreteDao>().As<IDao>();
builder.RegisterType<MessageConsumer>().As<IConsumer<Message>>();
builder.AddMassTransit(x => {
// add the bus to the container
x.UsingRabbitMq((context, cfg) => {
cfg.Host("localhost");
cfg.ReceiveEndpoint("MessageQueueName", ec => {
// Configure a single consumer
ec.ConfigureConsumer<MessageConsumer>(context);
});
// or, configure the endpoints by convention
cfg.ConfigureEndpoints(context);
});
});
var container = builder.Build();
var bc = container.Resolve<IBusControl>();
bc.Start();
}
However I am getting an exception when the IBusControl is resolved.
System.ArgumentException: 'The consumer type was not found: StationDashboard.Messaging.Consumer.OperationModeChangedConsumer (Parameter 'T')'
What is wrong with the code above? What is the best way to inject dependency to a consumer? It would help if there was a complete working sample.
You need to register the consumer as explained in the documentation.
Do NOT do this:
builder.RegisterType<MessageConsumer>().As<IConsumer<Message>>();
Instead, as shown in the documentation, do this:
x.AddConsumer<MessageConsumer>();
Your dependency can be registered as you've done it.
Related
I'm trying to use MassTransit mediator on my Asp.Net web API. Currently I'm using Masstransit 7.3.0
I wanted for consumers to share the same scope. So I did everything step-by-step as in documentation.
Here I'm setting up the mediator in startup and adding the consumers, requestclients:
services.AddHttpContextAccessor();
services.AddMediator(cfg =>
{
cfg.ConfigureMediator((regContext, options) =>
{
options.UseHttpContextScopeFilter(regContext);
});
cfg.AddConsumer<BillingFile.Create>();
cfg.AddRequestClient<BillingFile.Command.CreateCommand>();
cfg.AddConsumer<Payment.CreateBasePayment>();
cfg.AddRequestClient<Payment.Command.CreateBasePaymentCommand>();
});
I'm using HttpContextScopeFilter directly from the documentation on the website.
When I try to send a message from one consumer to the other, an exception is thrown:
The ConsumeContext was already set
Here is my Create consumer:
public class Create : IConsumer<CreateCommand>
{
private readonly IMediator mediator;
public Create(IMediator mediator)
{
this.mediator = mediator;
}
public async Task Consume(ConsumeContext<CreateCommand> context)
{
var request = context.Message.Request;
/* Create base payment <--- here be the exception */
var basePaymentHandler = mediator.CreateRequestClient<CreateBasePaymentCommand>(context);
var basePaymentResponse = await basePaymentHandler.GetResponse<CreateBasePaymentResponse>(new CreateBasePaymentCommand { Request = Request, CorrelationId = Guid.NewGuid()}, cancellationToken: context.CancellationToken);
....
Is this not allowed by Masstransit mediator?
MassTransit won't let you dispatch multiple messages in the same container scope. It results in the very exception you are experiencing. You're also using an obsolete/unsupported version of MassTransit.
In X class, I have the following code block, and I'm facing with "'QueueConsumer' must be a non-abstract type with a public parameterless constructor in order to use it as parameter 'TConsumer' in the generic type or method 'ConsumerExtensions.Consumer(IReceiveEndpointConfigurator, Action<IConsumerConfigurator>)'" error.
cfg =>
{
cfg.Host(ServiceBusConnectionString);
cfg.ReceiveEndpoint(router.Name, e =>
{
e.Consumer<QueueConsumer>(); // I got the error in this line
});
}
In QueueConsumer, I use IConfiguration class with dependency injection. I know, if I use empty constructor I won't see above error but then I can't use IConfiguration. This is my QueueConsumer class:
public class QueueConsumer : IConsumer<TransferMessage>
{
public readonly IConfiguration _configuration;
public QueueConsumer(IConfiguration configuration)
{
_configuration = configuration;
}
So, do you any idea for how to avoid this problem? How can I use dependency injection with parameterless constructor?
Masstransit supports factories for the consumer:
Taken from the above link:
cfg.ReceiveEndpoint("order-service", e =>
{
// delegate consumer factory
e.Consumer(() => new SubmitOrderConsumer());
// another delegate consumer factory, with dependency
e.Consumer(() => new LogOrderSubmittedConsumer(Console.Out));
// a type-based factory that returns an object (specialized uses)
var consumerType = typeof(SubmitOrderConsumer);
e.Consumer(consumerType, type => Activator.CreateInstance(consumerType));
});
So you can inject any dependency you want here. You should also be able to use whatever DI Framework you want in/as such a factory method.
However, if you are using ASP.Net Core DI, please read the following for the integration that MassTransit has built in:
https://masstransit-project.com/usage/configuration.html#asp-net-core
I assume you are using MassTransit with RabbitMQ and vanilla DI for ASP.NET Core in this case you can do it.
You might need to add NuGet MassTransit.Extensions.DependencyInjection
When configuring services with AddMassTransit you need to use AddConsumer[s]
When configuring rabbit with UsingRabbitMq you need to use ConfigureConsumer
The final code might look similar to this (a snippet for hosted service in .Net 6)
// some code above
Host.CreateDefaultBuilder().ConfigureServices((hostContext, services) =>
{
services.AddMassTransit(
opt =>
{
// Add all consumers from the assembly
opt.AddConsumers(typeof(CoolConsumer).Assembly);
opt.UsingRabbitMq((context, cfg) =>
{
// Spin up the RabbitMQ bus with values from config
cfg.Host(hostContext.Configuration["RabbitMQ:Host"],
hostContext.Configuration["RabbitMQ:VirtualHost"], h =>
{
h.Username(hostContext.Configuration["RabbitMQ:Username"]);
h.Password(hostContext.Configuration["RabbitMQ:Password"]);
});
cfg.ReceiveEndpoint("my-queue-name", p =>
{
p.ConfigureConsumer<CoolConsumer>(context);
});
});
});
});
// some additional code
I am working on Azure WebJobs (3.0.6) using dotnet core. I referred Microsoft's Get Started Guide. Per the example I wanted to have a console logging to begin with. The scope of that guide is limited. In my application, I will be using many classes in a different dll. I am not able to figure out how can I add logging in those classes. The sample code is
// The main method
static async Task Main()
{
var builder = new HostBuilder();
builder.ConfigureWebJobs(b =>
{
b.AddAzureStorageCoreServices();
b.AddAzureStorage();
});
builder.ConfigureLogging((context, b) =>
{
b.AddConsole();
});
var host = builder.Build();
using (host)
{
await host.RunAsync();
}
}
// The queue trigger class
public class QueueListenerService
{
public static void QueueListener([QueueTrigger("myqueue")] string message, ILogger logger)
{
logger.LogInformation("The logger works here");
// how can I pass an instance of ILogger in the constructor below
MyWorker myWorker = new MyWorker();
}
}
// MyWorker Class in a different assembly
public class MyWorker
{
public MyWorker(ILogger logger)
{
// I want to use logger here being injected
}
}
I have referred several examples of DI in dotnet core console applications and they use service collection approach. I also check this blog but to me, this is what I have done and yet my ILogger is not being resolved. It ask me to pass an instance of ILogger when I create MyWorker instance
You are close to the solution. The main thing you need to change is to let the service collection create the MyWorker instance for you.
I quickly extended my recent Webjob sample project to include console logging with dependency injection. See this commit for how I added it.
You mainly need to use constructor dependency injection for your QueueListenerService.
builder.ConfigureServices(services =>
{
services.AddScoped<QueueListenerService>();
services.AddScoped<MyWorker>();
});
public class QueueListenerService
{
public QueueListenerService(MyWorker worker){
_Worker = worker;
}
public static void QueueListener([QueueTrigger("myqueue")] string message, ILogger logger)
{
logger.LogInformation("The logger works here");
_Worker.DoStuff()
}
}
I am studying MassTransit and ASP.NET Core, dependancy injection and successfully implemented something that works. I plan to use the Kestrel web server.
So I had to configure my ASP.NET core project this way in the Startup.cs.
public void ConfigureServices(IServiceCollection services) {
...
var bus = Bus.Factory.CreateUsingRabbitMq(sbc => {
var host = sbc.Host(new Uri(address), h => {
h.Username("guest");
h.Password("guest");
});
});
services.AddSingleton<IBus>(bus);
services.AddScoped<IRequestClient<GetTagRequest, GetTagAnswer>>(x =>
new MessageRequestClient<GetTagRequest, GetTagAnswer>(x.GetRequiredService<IBus>(), new Uri(address + "/gettagrequest"), timeOut));
bus.Start(); // <= ok. how is the bus supposed to stop ?
...
Although this works fine, no tutorial mentioned anything about setting bus.Stop() in an ASP.NET core project. I read in MassTransit documentation that a running bus could prevent a graceful exit.
Is this a major concern for a Kestrel web server? I have read about process recycling and I am afraid a running bus would compromise this.
At which place can I place that bus.Stop() in an ASP.NET Core project ?
You can use ApplicationLifetime events. Just make your IBus object class level variable.
public class Startup
{
private IBus _bus;
public void ConfigureServices(IServiceCollection services) {
/* ... */
_bus = Bus.Factory.CreateUsingRabbitMq ...
/* ... */
}
public void Configure(IApplicationLifetime appLifetime)
{
appLifetime.ApplicationStarted.Register(() => _bus.Start());
appLifetime.ApplicationStopping.Register(() => _bus.Stop());
}
}
There is IApplicationLifetime in .NET Core, which has several CancellationToken properties, including ApplicationStopped. So when you need to do something after asp.net application is shutdown and all requests are processed (like stopping your bus) - you can do it like this:
// lifetime will be injected to Configure from DI container
public void Configure(IApplicationBuilder app, IApplicationLifetime lifetime) {
// subscribe to ApplicationStopped
lifetime.ApplicationStopped.Register(OnApplicationStopped);
// the rest
}
private void OnApplicationStopped() {
_bus.Stop();
}
It's always good to explicitly release resources even on process shutdown. For example, some message might still be in transition when the process will be killed after shutdown. Doing explicit dispose will allow this transition to complete.
To add to the existing answers:
If you use the MassTransit.AspNetCore's IServiceCollection.AddMassTransit() extension method, there's no need for a class level IBus instance. Startup's Configure() supports DI, so you can do this instead:
public void Configure(IApplicationLifetime appLifetime, IBus bus)
{
appLifetime.ApplicationStarted.Register(() => bus.Start());
appLifetime.ApplicationStopping.Register(() => bus.Stop());
}
If you don't want to use the package, you can still register IBus with the DI container (like in the question) and request it from Configure().
The ASP.NET Core DI sample uses an IHostedService instead:
public class BusService : IHostedService
{
private readonly IBusControl _busControl;
public BusService(IBusControl busControl)
{
_busControl = busControl;
}
public Task StartAsync(CancellationToken cancellationToken) =>
_busControl.StartAsync(cancellationToken);
public Task StopAsync(CancellationToken cancellationToken) =>
_busControl.StopAsync(cancellationToken);
}
The service is registered as:
services.AddSingleton<IHostedService, BusService>();
For more information on IHostedService, here's the doc page. I'm not sure I like the idea of having a background service just to stop the bus. Anyway, the sample repo I picked this example from is worth referring to.
The third option is to do it yourself in Main(). Something like:
var host = CreateWebHostBuilder(args).Build();
var bus = host.Services.GetRequiredService<IBusControl>();
await bus.StartAsync();
await host.RunAsync();
await bus.StopAsync();
Background
I'm trying to set up a Web API 2 which needs to communicate to a NServicebus Endpoint.
I will need to implement IoC, which will be done using Autofac.
What I have
A controller defined like so:
[RoutePrefix("api")]
public class Controller : ApiController
{
private IEndpointInstance EndpointInstance { get; set; }
public public MyController(IEndpointInstance endpointInstance)
{
this.EndpointInstance = endpointInstance;
}
[HttpGet]
[Route("dostuff")]
public async Task DoStuff()
{
var command = new MyCommand
{
...
};
await this.EndpointInstance.SendLocal(command);
}
}
And in global.asax
Application_Start
protected async void Application_Start()
{
GlobalConfiguration.Configure(WebApiConfig.Register);
await RegisterNServiceBusWithAutofac();
}
RegisterNServiceBusWithAutofac
private async Task RegisterNServiceBusWithAutofac()
{
var builder = new ContainerBuilder();
var endpointConfiguration = await GetEndpointConfiguration("My.Service");
var endpointInstance = await Endpoint.Start(endpointConfiguration);
builder.RegisterInstance(endpointInstance);
var container = builder.Build();
endpointConfiguration.UseContainer<AutofacBuilder>(c => c.ExistingLifetimeScope(container));
builder.RegisterApiControllers(Assembly.GetExecutingAssembly());
}
GetEndpointConfiguration
private static async Task<EndpointConfiguration> GetEndpointConfiguration(string name)
{
var endpointConfiguration = new EndpointConfiguration(name);
// Set transport.
var routing = endpointConfiguration.UseTransport<MsmqTransport>().Routing();
// Register publish to self
routing.RegisterPublisher(typeof(EventHasFinished), name);
endpointConfiguration.UseSerialization<JsonSerializer>();
endpointConfiguration.UsePersistence<InMemoryPersistence>();
endpointConfiguration.SendFailedMessagesTo("error");
endpointConfiguration.EnableInstallers();
return endpointConfiguration;
}
The result
I get the following error on the UseContainer line:
Unable to set the value for key:
NServiceBus.AutofacBuilder+LifetimeScopeHolder. The settings has been
locked for modifications. Move any configuration code earlier in the
configuration pipeline
What I think this means
I think I need to do all Autofac registrations for the NServicebus when creating the endpointConfiguration. The above manipulates the builder instance after that.
But
I can't do the above, because I need to register the endpointinstance to the IoC, because I need that in my controller to send messages. And that doesn't exist yet, because I need the endpointConfiguration first, for that.
So I have a chicken and egg situation ...
Question
Do I understand the issue correctly and how can I solve it while
making sure that IoC works correctly for the Controller?
I.e.: this.EndpointInstance has been correctly instantiated through IoC.
Instead of registering the actual instance, you could register it with a lambda expression that is going to be executed the first time the container will be asked to resolve IEndpointInstance.
builder
.Register(x =>
{
var endpointConfiguration = GetEndpointConfiguration("My.Service").GetAwaiter().GetResult();
var endpointInstance = Endpoint.Start(endpointConfiguration).GetAwaiter().GetResult();
return endpointInstance
})
.As<IEndpointInstance>()
.SingleInstance();