Don't log an error when a BackgroundService is canceled due to the host being stopped.

src/libraries/Microsoft.Extensions.Hosting/src/Internal/Host.cs

@@ -22,6 +22,7 @@ internal sealed class Host : IHost, IAsyncDisposable
  private readonly IHostEnvironment _hostEnvironment;
  private readonly PhysicalFileProvider _defaultProvider;
  private IEnumerable<IHostedService> _hostedServices;
+ private volatile bool _stopCalled;
 
  public Host(IServiceProvider services,
  IHostEnvironment hostEnvironment,
@@ -84,6 +85,13 @@ private async Task TryExecuteBackgroundServiceAsync(BackgroundService background
  }
  catch (Exception ex)
  {
+ // When the host is being stopped, it cancels the background services.
+ // This isn't an error condition, so don't log it as an error.
+ if (_stopCalled && backgroundService.ExecuteTask.IsCanceled && ex is OperationCanceledException)
+ {
+ return;
+ }
+
  _logger.BackgroundServiceFaulted(ex);
  if (_options.BackgroundServiceExceptionBehavior == BackgroundServiceExceptionBehavior.StopHost)
  {
@@ -95,6 +103,7 @@ private async Task TryExecuteBackgroundServiceAsync(BackgroundService background
 
  public async Task StopAsync(CancellationToken cancellationToken = default)
  {
+ _stopCalled = true;
  _logger.Stopping();
 
  using (var cts = new CancellationTokenSource(_options.ShutdownTimeout))

src/libraries/Microsoft.Extensions.Hosting/tests/UnitTests/Internal/HostTests.cs

@@ -1367,6 +1367,45 @@ public async Task BackgroundServiceAsyncExceptionGetsLogged(
  }
  }
 
+ /// <summary>
+ /// Tests that when a BackgroundService is canceled when stopping the host,
+ /// no error is logged.
+ /// </summary>
+ [Fact]
+ public async Task HostNoErrorWhenServiceIsCanceledAsPartOfStop()
+ {
+ using TestEventListener listener = new TestEventListener();
+
+ using IHost host = CreateBuilder()
+ .ConfigureLogging(logging =>
+ {
+ logging.AddEventSourceLogger();
+ })
+ .ConfigureServices(services =>
+ {
+ services.AddHostedService<AsyncWaitingService>();
+ })
+ .Build();
+
+ host.Start();
+ await host.StopAsync();
+
+ EventWrittenEventArgs[] events =
+ listener.EventData.Where(
+ e => e.EventSource.Name == "Microsoft-Extensions-Logging").ToArray();
+
+ foreach (EventWrittenEventArgs eventArg in events)
+ {
+ int levelIndex = eventArg.PayloadNames.IndexOf("Level");
+ LogLevel level = (LogLevel)eventArg.Payload[levelIndex];
+ Assert.True(level < LogLevel.Error);
+
+ int eventNameIndex = eventArg.PayloadNames.IndexOf("EventName");
+ string eventName = (string)eventArg.Payload[eventNameIndex];
+ Assert.NotEqual("BackgroundServiceFaulted", eventName);
+ }
+ }
+
  private IHostBuilder CreateBuilder(IConfiguration config = null)
  {
  return new HostBuilder().ConfigureHostConfiguration(builder => builder.AddConfiguration(config ?? new ConfigurationBuilder().Build()));
@@ -1513,5 +1552,18 @@ protected override async Task ExecuteAsync(CancellationToken stoppingToken)
  throw new Exception("Background Exception");
  }
  }
+
+ private class AsyncWaitingService : BackgroundService
+ {
+ public AsyncWaitingService() { }
+
+ protected override async Task ExecuteAsync(CancellationToken stoppingToken)
+ {
+ while (!stoppingToken.IsCancellationRequested)
+ {
+ await Task.Delay(1000, stoppingToken);
+ }
+ }
+ }
  }
 }