CODEWITHSUNDEEP
asp.net-coreasp.net-core-2.0asp.net-core-webapi
Rasula Caldera
Rasula Caldera

Reputation: 305

Running multiple backend services using iHostedService

Currently my web API is able to run on a schedule and trigger another end point in order to sync data. The services that needs to be called are stored in a yml file. I have managed to get it working for one service to run a schedule. What I want is to be able to save multiple endpoints with schedules of their own and for them to be scheduled and executed at the right time.

Here is the code that I have now

I have done this using iHostedService interface.

This is the HostService class that implements iHostedService

public abstract class HostedService : IHostedService
{
    private Task _executingTask;
    private CancellationTokenSource _cts;

    public Task StartAsync(CancellationToken cancellationToken)
    {
        _cts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);

        _executingTask = ExecuteAsync(_cts.Token);

        // If the task is completed then return it, otherwise it's running
        return _executingTask.IsCompleted ? _executingTask : Task.CompletedTask;
    }

    public async Task StopAsync(CancellationToken cancellationToken)
    {
        // Stop called without start
        if (_executingTask == null)
        {
            return;
        }

        // Signal cancel
        _cts.Cancel();

        // Wait until the task completes or the stop token triggers
        await Task.WhenAny(_executingTask, Task.Delay(-1, cancellationToken));

        cancellationToken.ThrowIfCancellationRequested();
    }

    // cancel
    protected abstract Task ExecuteAsync(CancellationToken cancellationToken);
}

I am then extending this class and implementing what needs to be done in the ExecuteAsync as follows 

public class DataRefreshService : HostedService
{
    private readonly DataFetchService _dataFetchService;

    public DataRefreshService(DataFetchService randomStringProvider)
    {
        _dataFetchService = randomStringProvider;
    }

    protected override async Task ExecuteAsync(CancellationToken cancellationToken)
    {
        try
        {
            while (!cancellationToken.IsCancellationRequested)
            {
                await _dataFetchService.UpdateData(cancellationToken);

                TimeSpan span = _dataFetchService.GetNextTrigger();

                await Task.Delay(span, cancellationToken);
            }
        } catch (Exception)
        {
            await StopAsync(cancellationToken);
            throw new Exception("Error trigger Sync service");
        }
    }
}

This is what I have added to the Startup.cs file 

services.AddSingleton<DataFetchService>();
services.AddSingleton<IHostedService, DataRefreshService>();

Upvotes: 2

Views: 1367

Answers (1)

user2258403
user2258403

Reputation: 786

You could try 

services.AddHostedService<DataRefreshService>;

You could also try in making the DataRefreshService inherit from 

Microsoft.Extensions.Hosting.BackgroundService

You can read more about that here

Upvotes: 1

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