Background Services

A background service is a service that runs in the background, independent of the traditional request-response HTTP model.

Wisp injects dependencies and takes care of managing your service's lifecycle for you.

Writing a Background Service

A background service must implement the IBackgroundService interface. Any constructor arguments will be injected.

public class HelloWorldBackgroundService : IBackgroundService 
{
    private readonly HelloWorldService _hws;

    public HelloWorldBackgroundService(HelloWorldService hws)
    {
        // Injected from DI
        _hws = hws;
    }

    public async Task RunAsync(CancellationToken cancellationToken) 
    {
        try 
        {
            while(!cancellationToken.IsCancellationRequested) 
            {
                await hws.SayHelloWorldAsync();
                await Task.Delay(TimeSpan.FromSeconds(5))
            }    
        }
        catch (TaskCanceledException) {}        
    }
}

Long-Running Services

Wisp will instantiate your service, inject arguments and them call RunAsync exactly once when the application starts, and then cancel the CancellationToken when the application is exiting.

If you need your service to keep running in the background, it is up to you to do so. The recommended way of achieving this is a while loop that keeps running until the token is canceled. Don't forget to wrap this in a try/catch and handle the TaskCanceledException, which, in this case, does not indicate an error.

Registering a Background Service

Use the AddBackgroundService<T> extension method.

var hostBuilder = new new WispHostBuilder();

hostBuilder.AddBackgroundService<HelloWorldBackgroundService>();

var appBuilder = hostBuilder.Build();
var app = appBuilder.Build();

await app.RunAsync();

Starting Background Services

Background services start automatically on application start.

Stopping Background Services

Wisp will automatically cancel the CancellationToken passed to RunAsync when the application is shutting down. If you need to be able to stop the service from elsewhere, you can pass on the cancellation token instance from within RunAsync.

Passing your own CancellationToken to RunAsync is currently not supported.