ASP.Net core 3.1中如何启动BackgroundService API

Question

I have tried to follow this tutorial on how to create a backgroundworker.

Most of the stuff wasn't useful for me, so I didn't include that. I have no need for a queue. I just need to have this backgroundworker running in the background doing stuff every X hours My worker looks like this. Unfortunately it seems like it never calls the ExecuteAsync method

public class EnergySolutionBackgroundWorker : BackgroundService
{       
    private readonly ILogger<EnergySolutionBackgroundWorker> _logger;

    public EnergySolutionBackgroundWorker(ILogger<EnergySolutionBackgroundWorker> logger)
    {         
        _logger = logger;
    }

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        _logger.LogInformation("{Type} is now running in the background.", nameof(BackgroundWorker));

        await BackgroundProcessing(stoppingToken);
    }

    public override Task StopAsync(CancellationToken cancellationToken)
    {
        _logger.LogCritical("The {Type} is stopping due to a host shutdown.", nameof(BackgroundWorker));

        return base.StopAsync(cancellationToken);
    }

    private async Task BackgroundProcessing(CancellationToken stoppingToken)
    {
        while (!stoppingToken.IsCancellationRequested)
        {
            try
            {
                await Task.Delay(new TimeSpan(0, 0, 1), stoppingToken);

                // Doing some tasks
            }
            catch (Exception ex)
            {
                _logger.LogCritical("An error occurred when publishing a book. Exception: {@Exception}", ex);
            }
        }
    }        
}

In Startup.cs I have the following:

public void ConfigureServices(IServiceCollection services)
    {
        services.AddControllers();

        services.AddHostedService<EnergySolutionBackgroundWorker>();
    }

From my understanding, this should be enough for it to automatically start the backgroundworker during startup, but that is not the case. What am I doing wrong?

Answer 1

1. you can add timer in start function. A timed background task makes use of the System.Threading.Timer class. The timer triggers the task's DoWork method. The timer is disabled on StopAsync and disposed when the service container is disposed on Dispose:

internal class TimedHostedService : IHostedService, IDisposable
{
    private readonly ILogger _logger;
    private Timer _timer;

    public TimedHostedService(ILogger<TimedHostedService> logger)
    {
        _logger = logger;
    }

    public Task StartAsync(CancellationToken cancellationToken)
    {
        _logger.LogInformation("Timed Background Service is starting.");

        _timer = new Timer(DoWork, null, TimeSpan.Zero, 
            TimeSpan.FromSeconds(5));

        return Task.CompletedTask;
    }

    private void DoWork(object state)
    {
        _logger.LogInformation("Timed Background Service is working.");
    }

    public Task StopAsync(CancellationToken cancellationToken)
    {
        _logger.LogInformation("Timed Background Service is stopping.");

        _timer?.Change(Timeout.Infinite, 0);

        return Task.CompletedTask;
    }

    public void Dispose()
    {
        _timer?.Dispose();
    }
}

2. there is a reference

Answer 2

I believe I found the answer. Startup.cs is not run before the first call to the API is made, After calling a simple Test method in one of my controllers, the BackgroundProcessing method was called That's a bit annoying, as I was hoping I later could create a backgroundworker that loads a lot of data into memory instead of it happening when the first call is made