NServiceBus.Extensions.DependencyInjection can't be used

[DavidBoike]

If you want to create a send-only endpoint, a ServiceBusTriggeredEndpointConfiguration doesn't make any sense, as there won't be a queue.

But setting up a send-only NServiceBus endpoint using NServiceBus.Extensions.DependencyInjection won't work either, because the .UseNServiceBus(…) extension method doesn't support IFunctionsHostBuilder.

I think this also affects the InProcess hosting model as IFunctionsHostBuilder is located in Microsoft.Azure.Functions.Extensions.DependencyInjection.

[timbussmann]

@DavidBoike shouldn't this issue be focused on support for send-only configurations rather than on using Microsoft.Azure.Functions.Extensions.DependencyInjection then?

[DavidBoike]

Perhaps. I wrote the issue at the time based on the problem the customer was having.

[timbussmann]

FYI #220 also describes a workaround that should allow using "SendOnly" mode (using no trigger or message pump)

[timbussmann]

Using the worker mode, I think someting like the following approach should work as a workaround (also enabling usage of different transports to send messages) but I'd rather have a better integration with the known UseNServiceBus config API.

var host = new HostBuilder()
    .ConfigureFunctionsWorkerDefaults()
    .ConfigureServices(serviceCollection =>
    {
        var configuration = new EndpointConfiguration("SendOnlyEndpoint");

        var routing = configuration.UseTransport(new AzureServiceBusTransport(Environment.GetEnvironmentVariable(...)));

        configuration.SendOnly();

        var startableEndpoint = EndpointWithExternallyManagedContainer.Create(configuration, serviceCollection);

        serviceCollection.AddHostedService(sp => new NServiceBusService(sp, startableEndpoint));
        // inject IMessageSession into the function ctor:
        serviceCollection.AddSingleton<IMessageSession>(sp => NServiceBusService.endpointInstance);
    })
    .Build();

host.Run();


class NServiceBusService : IHostedService
{
    // if accessing too early, this will be null
    public static IEndpointInstance endpointInstance = null!;

    IServiceProvider serviceProvider;
    IStartableEndpointWithExternallyManagedContainer startableEndpoint;

    public NServiceBusService(IServiceProvider serviceProvider, IStartableEndpointWithExternallyManagedContainer startableEndpoint)
    {
        this.serviceProvider = serviceProvider;
        this.startableEndpoint = startableEndpoint;
    }

    public async Task StartAsync(CancellationToken cancellationToken)
    {
        var endpoint = await startableEndpoint.Start(serviceProvider);
        endpointInstance = endpoint;
    }

    public Task StopAsync(CancellationToken cancellationToken)
    {
        return endpointInstance.Stop();
    }
}

note that this doesn't properly configure logging in NServiceBus, so this isn't production ready code.