How should a service exit to prevent an error?

Question

I'm developing a Windows service in C#, .NET 6.0 following the instructions on https://learn.microsoft.com/en-us/do.net/core/extensions/windows-service The service runs as expected, but when I stop the service, it logs an error

A task was canceled.

Exception: System.Threading.Tasks.TaskCanceledException: A task was canceled. at AWLService.WindowsBackgroundService.ExecuteAsync(CancellationToken stoppingToken) in C:\Minerva\Projects\AWLService_Test\WindowsBackgroundService.cs:line 22

The ExecuteAsync for this program is as follows:

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        try
        {
            while (!stoppingToken.IsCancellationRequested)
            {
                string joke = _jokeService.GetJoke();
                _logger.LogWarning("{Joke}", joke);

                await Task.Delay(TimeSpan.FromMinutes(1), stoppingToken);
            }
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "{Message}", ex.Message);

            // Terminates this process and returns an exit code to the operating system.
            // This is required to avoid the 'BackgroundServiceExceptionBehavior', which
            // performs one of two scenarios:
            // 1. When set to "Ignore": will do nothing at all, errors cause zombie services.
            // 2. When set to "StopHost": will cleanly stop the host, and log errors.
            //
            // In order for the Windows Service Management system to leverage configured
            // recovery options, we need to terminate the process with a non-zero exit code.
            Environment.Exit(1);
        }
    }

I've tried catching TaskCanceledException. When I do that and add Environment.Exit(0), I still get the error. If I take out Environment.Exit, the service terminates without an error, but it logs "Service stopped successfully" twice.

What is the proper way I should be ending my service?

Thank you.

EDIT: I added a handler for TaskCanceledException as follows:

catch (TaskCanceledException ex)
{
    //Do nothing, we're exiting normally.
    Environment.Exit(0);
}

When I do that, stopping the service through MMC shows an error "Error 1067: The process terminated unexpectedly" and a message is not logged indicating the service was stopped. Stopping it with sc on the command line doesn't show an error, but it also doesn't log a message that the service was stopped.

If I remove the Environment.Exit(0) line, MMC no longer shows an error, but the "Service stopped successfully" log message is written twice.

Answer 1

Catch the OperationCancelledException and log something different to the console in the handler. I suspect in your original handler (not shown) you were still probably doing this: _logger.LogError(ex, "{Message}", ex.Message);

protected override async Task ExecuteAsync(CancellationToken stoppingToken)
{
    try
    {
        while (!stoppingToken.IsCancellationRequested)
        {
            string joke = _jokeService.GetJoke();
            _logger.LogWarning("{Joke}", joke);

            await Task.Delay(TimeSpan.FromMinutes(1), stoppingToken);
        }
    }
    catch (OperationCancelledException)
    {
        _logger.LogInformation("The service has stopped");
        Environment.Exit(0);
    }
    catch (Exception ex)
    {
        _logger.LogError(ex, "{Message}", ex.Message);
    }
}