How to use .NET Core's Built in Dependency Injection with Service Fabric

Question

Good afternoon,

I recently started experimenting with Service Fabric and .NET Core. I created a Stateless Web API and performed some DI using:

public void ConfigureServices(IServiceCollection services)
{
    services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_2);
    var connString = Configuration.GetConnectionString("DefaultConnection");
    services.AddScoped<FaxLogic>();
    services.AddDbContext<ApplicationContext>(options => options.UseSqlServer(connString));
}

With the above I can use constructor inject on my FaxLogic class as well as my DbContext class (through the FaxLogic):

private readonly FaxLogic _faxLogic;
public FaxController(
    FaxLogic faxLogic)
{
    _faxLogic = faxLogic;
}

private readonly ApplicationContext _context;
public FaxLogic(ApplicationContext context)
{
    _context = context;
}

I then created a non-Web API stateless service. I want to be able to access my FaxLogic and DbContext like in my WebAPI, but within the RunAsync method of the stateless service:

protected override async Task RunAsync(CancellationToken cancellationToken)
{
    // TODO: Replace the following sample code with your own logic 
    //       or remove this RunAsync override if it's not needed in your service.

    while (true)
    {
        cancellationToken.ThrowIfCancellationRequested();

        ServiceEventSource.Current.ServiceMessage(this.Context, "Hello!");

        // do db stuff here!

        await Task.Delay(TimeSpan.FromSeconds(5), cancellationToken);
    }
}

I am wondering how I'd do it. I tried playing with the CreateServiceInstanceListeners() method and the Program.cs file where ServiceRuntime is is used to register but I can't seem to figure it out! Any help would be appreciated.

Answer 1

The solution has been already answered here: Set up Dependency Injection on Service Fabric using default ASP.NET Core DI container

In summary, you have to register the dependencies before you create a new instance of your stateless service and then create a factory method to resolve the dependencies:

i.e:

public static class Program
{
    public static void Main(string[] args)
    {
        var provider = new ServiceCollection()
                    .AddLogging()
                    .AddSingleton<IFooService, FooService>()
                    .AddSingleton<IMonitor, MyMonitor>()
                    .BuildServiceProvider();

        ServiceRuntime.RegisterServiceAsync("MyServiceType",
            context => new MyService(context, provider.GetService<IMonitor>());
        }).GetAwaiter().GetResult();

See the linked answer for more details.

Answer 2

TaeSeo,

I think what you are looking for is implemented in the project I am working on - CoherentSolutions.Extensions.Hosting.ServiceFabric.

In the terms of CoherentSolutions.Extensions.Hosting.ServiceFabric what you are looking for would look like:

private static void Main(string[] args)
{
  new HostBuilder()
    .DefineStatelessService(
      serviceBuilder => {
        serviceBuilder
          .UseServiceType("ServiceName")
          .DefineDelegate(
            delegateBuilder => {
              delegateBuilder.ConfigureDependencies(
                dependencies => {
                  dependencies.AddScoped<FaxLogic>();
                });
              delegateBuilder.UseDelegate(
                async (StatelessServiceContext context, FaxLogic faxLogic) => {
                  while (true) {
                    cancellationToken.ThrowIfCancellationRequested();

                    ServiceEventSource.Current.ServiceMessage(context, "Hello!");

                    await Task.Delay(TimeSpan.FromSeconds(5), cancellationToken);
                });
            })
       })
    .Build()
    .Run();
}

If you have more questions feel free to ask or check out the project wiki

Hope it helps.