Missing Logging of Exceptions in IHostedService without await

[Tripletri]

Description

When an exception occures in IHostedService without calling await, it is not logged to the ILogger.
This make it difficult to identify the reason for the application shutdown when writing logs to an external service.

Reproduction Steps

IHost host = Host.CreateDefaultBuilder(args)
    .ConfigureServices(services =>
    {
        services.AddHostedService<Worker>();
    })
    .Build();

await host.RunAsync();

public class Worker : IHostedService
{
    public Task StartAsync(CancellationToken cancellationToken) =>
        throw new Exception();

    public Task StopAsync(CancellationToken cancellationToken) =>
        Task.CompletedTask;
}

Expected behavior

When an exception occurs within the StartAsync of IHostedService, whether or not method has await, the exception should be logged to the ILogger

Actual behavior

When an exception occurs in the StartAsync without calling await, the exception is not logged to the ILogger

Regression?

No response

Known Workarounds

No response

Configuration

Sdk: Microsoft.NET.Sdk.Worker
Framework: .NET 7.0.3

Other information

It is also lead to misunderstanding of BackgroundServiceExceptionBehavior.Ignore, which continue to stop host when exception occurs.

This can be relative to #67146

[ghost]

Tagging subscribers to this area: @dotnet/area-extensions-hosting
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Description

When an exception occures in IHostedService without calling await, it is not logged to the ILogger.
This make it difficult to identify the reason for the application shutdown when writing logs to an external service.

Reproduction Steps

IHost host = Host.CreateDefaultBuilder(args)
    .ConfigureServices(services =>
    {
        services.AddHostedService<Worker>();
    })
    .Build();

await host.RunAsync();

public class Worker : IHostedService
{
    public Task StartAsync(CancellationToken cancellationToken) =>
        throw new Exception();

    public Task StopAsync(CancellationToken cancellationToken) =>
        Task.CompletedTask;
}

Expected behavior

When an exception occurs within the StartAsync of IHostedService, whether or not method has await, the exception should be logged to the ILogger

Actual behavior

When an exception occurs in the StartAsync without calling await, the exception is not logged to the ILogger

Regression?

No response

Known Workarounds

No response

Configuration

Sdk: Microsoft.NET.Sdk.Worker
Framework: .NET 7.0.3

Other information

It is also lead to misunderstanding of BackgroundServiceExceptionBehavior.Ignore, which continue to stop host when exception occurs.

This can be relative to #67146

Author:	Tripletri
Assignees:	-
Labels:	untriaged, area-Extensions-Hosting
Milestone:	-

[buyaa-n]

It looks we did not had any exception hanlding for running hosted services:

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

Lines 68 to 77 in 417a015

	foreach (IHostedService hostedService in _hostedServices)
	{
	// Fire IHostedService.Start
	await hostedService.StartAsync(combinedCancellationToken).ConfigureAwait(false);
	if (hostedService is BackgroundService backgroundService)
	{
	_ = TryExecuteBackgroundServiceAsync(backgroundService);
	}
	}

This is updated recently with #84048 and #85191:

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

Lines 69 to 123 in 71c9c73

	List<Exception> exceptions = new List<Exception>();
	if (_options.ServicesStartConcurrently)
	{
	List<Task> tasks = new List<Task>();
	foreach (IHostedService hostedService in _hostedServices)
	{
	tasks.Add(Task.Run(() => StartAndTryToExecuteAsync(hostedService, combinedCancellationToken), combinedCancellationToken));
	}
	Task groupedTasks = Task.WhenAll(tasks);
	try
	{
	await groupedTasks.ConfigureAwait(false);
	}
	catch (Exception ex)
	{
	exceptions.AddRange(groupedTasks.Exception?.InnerExceptions ?? new[] { ex }.AsEnumerable());
	}
	}
	else
	{
	foreach (IHostedService hostedService in _hostedServices)
	{
	try
	{
	// Fire IHostedService.Start
	await StartAndTryToExecuteAsync(hostedService, combinedCancellationToken).ConfigureAwait(false);
	}
	catch (Exception ex)
	{
	exceptions.Add(ex);
	break;
	}
	}
	}
	if (exceptions.Count > 0)
	{
	if (exceptions.Count == 1)
	{
	// Rethrow if it's a single error
	Exception singleException = exceptions[0];
	_logger.HostedServiceStartupFaulted(singleException);
	ExceptionDispatchInfo.Capture(singleException).Throw();
	}
	else
	{
	var ex = new AggregateException("One or more hosted services failed to start.", exceptions);
	_logger.HostedServiceStartupFaulted(ex);
	throw ex;
	}
	}

So, the issues you are seeing might have already fixed. The repro you provided doesn't have a logger and the await that causing the logging work, so I cannot check. @Tripletri please tryout your code with the .NET 8 preview 5 bits and let us know.

[ghost]

This issue has been marked needs-author-action and may be missing some important information.

[Tripletri]

Yes, the issue is fixed in 8.0.100-preview.5.23301.12. Thanks!