Worker 服务意外停止工作

我有 .NET Core 3+ 辅助服务，每 10 秒检查“一些内容”。有一次，它“随机”停止这样做，我不确定为什么。到目前为止，它发生了两次，并且没有异常日志或类似的东西，所以我只能假设我应该添加一个try-catch在 ExecuteAsync 内部，但我的问题是：是否有任何已知问题可能导致工作人员停止执行的类似行为？

是的，没有取消请求（否则，我想它会记录消息“发件人正在停止”）。

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

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

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        _logger.LogInformation("Sender is starting");
        stoppingToken.Register(() => _logger.LogInformation("Sender is stopping"));

        while (!stoppingToken.IsCancellationRequested)
        {
            await Task.Delay(10000, stoppingToken);

            _logger.LogDebug("Worker running at: {time}", DateTimeOffset.Now);

            if (!stoppingToken.IsCancellationRequested)
                await SendPendingMessages();
        }
    }

    private async Task SendPendingMessages()
    {
        var list = ...

        foreach (var item in list)
        {
            try
            {
                // Do stuff as expected
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, ex.Message);
            }
        }
    }
}

到目前为止，它发生了两次，并且没有异常日志或类似的东西，所以我只能假设我应该在 ExecuteAsync 中添加一个 try-catch，但我的问题是：是否有任何已知问题可能导致类似的行为，其中工人就停止执行？

对我来说这听起来确实是个例外。默认情况下，the BackgroundService实施将ignore抛出的任何异常ExecuteAsync。如果引发异常ExecuteAsync，它会被忽略，并且服务会停止运行。

我总是推荐顶级的try/catch通过日志记录，这样您至少知道发生了这种情况：

protected override async Task ExecuteAsync(CancellationToken stoppingToken)
{
  _logger.LogInformation("Sender is starting");
  try
  {
    while (!stoppingToken.IsCancellationRequested)
    {
      await Task.Delay(10000, stoppingToken);
      _logger.LogDebug("Worker running at: {time}", DateTimeOffset.Now);
      if (!stoppingToken.IsCancellationRequested)
        await SendPendingMessages();
    }
  }
  catch (Exception ex) when (stoppingToken.IsCancellationRequested)
  {
    _logger.LogInformation("Sender is stopping");
  }
  catch (Exception ex) when (!stoppingToken.IsCancellationRequested)
  {
    _logger.LogError(ex, "Sender had error");
  }
}
  

与此相关的是，如果这是您认为的“关键”后台服务，那么您还需要当该服务停止时停止应用程序主机:

private readonly ILogger<Worker> _logger;
private readonly IHostApplicationLifetime _hostApplicationLifetime;

public Worker(ILogger<Worker> logger, IHostApplicationLifetime hostApplicationLifetime)
{
  _logger = logger;
  _hostApplicationLifetime = hostApplicationLifetime;
}

protected override async Task ExecuteAsync(CancellationToken stoppingToken)
{
  _logger.LogInformation("Sender is starting");
  try
  {
    while (!stoppingToken.IsCancellationRequested)
    {
      await Task.Delay(10000, stoppingToken);
      _logger.LogDebug("Worker running at: {time}", DateTimeOffset.Now);
      if (!stoppingToken.IsCancellationRequested)
        await SendPendingMessages();
    }
  }
  catch (Exception ex) when (stoppingToken.IsCancellationRequested)
  {
    _logger.LogInformation("Sender is stopping");
  }
  catch (Exception ex) when (!stoppingToken.IsCancellationRequested)
  {
    _logger.LogError(ex, "Sender had error");
  }
  finally
  {
    _hostApplicationLifetime.StopApplication();
  }
}