runtime: StopTheHostException should be made public to be dealt with gracefully

Description

In brief, StopTheHostException should be made public as it may need to be handled by framework users.

This commit introduced StopTheHostException thrown out of, ultimately, HostBuilder.Build() on, among other things, adding a migration to a EF/.NET Core 6.0 RC2 project.

The exception itself seems to be expected, and is supposed to be caught by HostFactoryResolver.

However, that private, formally undocumented exception reaches my code which I believe is quite a common pattern:

try
{
   CreateHostBuilder().Build().Run()
}
catch (Exception ex)
{
   _logger.Fatal(ex, "Unhandled exception");
   return 1;
}

The following output is produced on an attempt to add a migration:

PM> Add-Migration InitialCreate -Context PersistedGrantDbContext -OutputDir Migrations\PersistedGrantDbContext Build started… Build succeeded. 18:21:59 [FTL] Unhandled exception Microsoft.Extensions.Hosting.HostFactoryResolver+HostingListener+StopTheHostException: Exception of type ‘Microsoft.Extensions.Hosting.HostFactoryResolver+HostingListener+StopTheHostException’ was thrown. at Microsoft.Extensions.Hosting.HostFactoryResolver.HostingListener.OnNext(KeyValuePair`2 value) at System.Diagnostics.DiagnosticListener.Write(String name, Object value) at Microsoft.Extensions.Hosting.HostBuilder.Build() <snip> To undo this action, use Remove-Migration. PM>

Reproduction Steps

(1) Add try/catch similar to the above around IHostBulder.Build() in any .NET/EF Core 6.0 RC2 project, (2) Attempt to add a migration.

Expected behavior

StopTheHostException needs to be public and documented, to be able to be gracefully re-thrown. Alternatively, it should never propagate out of the framework.

Actual behavior

StopTheHostException is private, undocumented, and reaches customer code.

Regression?

Yes - introduced in .NET Core 6.

Known Workarounds

I fixed the issue with the following:

catch (Exception ex)
{
   string type = ex.GetType().Name;
   if (type.Equals("StopTheHostException", StringComparison.Ordinal))
   {
      throw;
   }

   _logger.Fatal(ex, "Unhandled exception");
   return 1;
}

Normally, I would use catch(StopTheHostException) or similar but I can’t because StopTheHostException is private.

Configuration

Any ASP.NET Core/EF project, and potentially other kinds of projects.

Other information

No response

About this issue

Original URL
State: closed
Created 3 years ago
Reactions: 26
Comments: 19 (15 by maintainers)

Commits related to this issue

Quickstart 4 - Add error handling for StopTheHost exception The EF CLI throws a starts up the host to read database configuration and then throws a StopTheHost exception to stop the host from doing a... — committed to josephdecock/Samples by josephdecock 2 years ago

Most upvoted comments

Video

We renamed StopTheHostException to HostAbortedException now that it’s a public type. (And sealed it, and added [Serializable] for .NET Framework interop concerns)

namespace Microsoft.Extensions.Hosting
{
    [Serializable]
    public sealed partial class HostAbortedException : Exception
    {
        public HostAbortedException() { }
        private HostAbortedException(System.Runtime.Serialization.SerializationInfo info, System.Runtime.Serialization.StreamingContext context) { }
        public HostAbortedException(string? message) { }
        public HostAbortedException(string? message, System.Exception? innerException) { }
    }
}

bartonjs on Mar 15, 2022

OK lets expose the exception. I’m sympathetic to the problems experienced here as well.

davidfowl on Mar 14, 2022

If that’s being done for other Exception-derived types, then yes. If not, then no 😄. (I don’t know off the top of my head, but that’s the formula)

bartonjs on May 16, 2022

@maryamariyan Thank you for waiting. I’ve been busy lately. The PR will be made this week.

deeprobin on May 2, 2022

When do you see this exception happen in practice? Locally during development right when adding Migrations right? Narrow doesn’t mean that its not important, but if there are more cases than we’re aware of, that would be nice to know.

davidfowl on Mar 11, 2022

@davidfowl - thoughts here? My assumption is that StopTheHostException is supposed to be an internal implementation detail.

Any idea on what the proper way to handle this would be?

my code is now:

protected void CreateHost()
{
    if (HostBuilder == null)
        throw new InvalidOperationException(nameof(HostBuilder) + " was null");

    try
    {
        Host = HostBuilder.Build();
            
        // Release resources
        HostBuilder = null;
    }
    catch (Exception e) when(e is not OperationCanceledException && e.GetType().Name != "StopTheHostException")
    {
        _logger?.LogCritical(e, "Caught exception whilst building Host");
        throw;
    }
}

I’m running into this ex with a custom bootstrapper and ef core - would this be the proper way to handle this?

sommmen on Mar 8, 2022