Deadlock when calling System.Environment.Exit(int exitCode) during Startup.Configure(..)

[armingerten]

In some situations my web application requires to immediately quit during start-up. When doing so via System.Environment.Exit(int exitCode), the dotnet process does not exit.

Minimal set-up to reproduce:

public static void Main(string[] args)
{
    var host = new WebHostBuilder()
        .UseKestrel()
        .UseStartup<Startup>()
        .Build();

    host.Run();
}

public override void Configure(IApplicationBuilder app)
{
	System.Environment.Exit(1);
}

It seems that in this scenario Set() will no longer be called on the instance of ManualResetEventSlim passed to AttachCtrlcSigtermShutdown(..) resulting in the Shutdown() method to block indefinitely.

https://github.com/aspnet/Hosting/blob/97c9510a95e676324ed8fa03d8b6dcf3b1c19ccf/src/Microsoft.AspNetCore.Hosting/WebHostExtensions.cs#L134-L162

One possible solution could be applying the WebHostOptions.ShutdownTimeout when waiting for the manual reset event.

System Info:

• dotnet core: 2.1
• Microsoft.AspNetCore.Hosting: 2.1.1

[Tratcher]

Are you using 2.0 or 2.1?

Have you considered throwing an exception from Startup.Configure rather than calling exit?

[armingerten]

Thanks for the quick reply!

I am using 2.1.

I considered throwing exceptions from Startup.Configure, but I am using a JSON-based log-format and would like to keep the stacktrace in one log-entry (rather than plain-text, line-separated).

[muratg]

@Tratcher a bug?

[Tratcher]

Yes, with a workaround.

[b0wter]

I am encountering the same behaviour. When throwing an exception instead it results in the same behaviour. As strack trace is written and I am stuck at

Application is shutting down...

I am running 2.1 on Linux (Fedora).

[alex-sherman]

I encounter the same behavior in 2.2. I had relied on Environment.Exit in 2.0 on Linux/Windows without problem, but now in 2.2 it hangs on both Windows and Linux. Attached is a debugger which I believe shows the deadlock in the console logger.

[dadude999]

I see the same issue on Windows. One workaround appears to be simply P/Invoking the native C exit function in a class somewhere as follows:

private const string NativeCLibName = "ucrtbase.dll"; // assumes Windows; on Mac it will be "libSystem.dylib", on Linux probably "libc.so"

private const string ExitFunctionNativeName = "exit";

[DllImport(NativeCLibName, EntryPoint = ExitFunctionNativeName)]
public static extern void NativeExit(int exitCode);

Then wherever you would have called Environment.Exit, just call NativeExit instead.

[davidfowl]

If we can reproduce this with the generic host then we can move this to dotnet/runtime. It might require changes there anyways.

Thanks for contacting us.
We're moving this issue to the Next sprint planning milestone for future evaluation / consideration. Because it's not immediately obvious that this is a bug in our framework, we would like to keep this around to collect more feedback, which can later help us determine the impact of it. We will re-evaluate this issue, during our next planning meeting(s).
If we later determine, that the issue has no community involvement, or it's very rare and low-impact issue, we will close it - so that the team can focus on more important and high impact issues.
To learn more about what to expect next and how this issue will be handled you can read more about our triage process here.

[davidfowl]

This isn't something we want to fix in the webhost, but we should fix this in the generic host.