WebHost inside Generic host not logging startup messages

If you have a generic host, then inside this host you add a web host, and you are using .UseSerilog() for both, then the web host startup messages are not logged to Serilog.

This is what I mean by “startup messages”:

Hosting environment: Production Content root path: C:\Users\Me\Project\src\App\bin\Debug\netcoreapp3.0 Now listening on: http://localhost:5000 Application started. Press Ctrl+C to shut down.

Program.cs

public static async Task Main(string[] args)
{
    Log.Logger = new LoggerConfiguration()
        .MinimumLevel.Debug()
        .MinimumLevel.Override("Microsoft", LogEventLevel.Information)
        .Enrich.FromLogContext()
        .WriteTo.Console()
        .CreateLogger();

    IHostBuilder builder = new HostBuilder()
        .UseSerilog()
        .ConfigureServices(services => { collection.AddHostedService<MyService>(); });

    await builder.RunConsoleAsync();
}

MyService.cs

public class MyService : IHostedService
{
    private IWebHost _webHost;

    public async Task StartAsync(CancellationToken ct)
    {
        _webHost = WebHost.CreateDefaultBuilder()
            .UseStartup<MyService>()
            .UseSerilog()
            .Build();

        _webHost.RunAsync();
    }

    public async Task StopAsync(CancellationToken ct)
    {
        await _webHost.StopAsync();
    }

    public void ConfigureServices(IServiceCollection services) {
    }

    public void Configure(IApplicationBuilder app, IWebHostEnvironment env) {
    }
}

When this starts the logging from the generic host uses Serilog, but the logging in the web host startup does not. Logging of requests to the web host, on the other hand, does use Serilog. This is apparent in the output:

Hosting environment: Production Content root path: C:\Users\Me\Project\src\App\bin\Debug\netcoreapp3.0 Now listening on: http://localhost:5000 Application started. Press Ctrl+C to shut down. [15:32:01 INF] Application started. Press Ctrl+C to shut down. [15:32:01 INF] Hosting environment: Production [15:32:01 INF] Content root path: C:\Users\Me\Project\src\App\bin\Debug\netcoreapp3.0
[15:32:33 INF] Request starting HTTP/1.1 GET http://localhost:5000/ [15:32:33 INF] Request finished in 13.2002ms 404

Expected behaviour

The startup messages from a web host inside a generic host should still be logged to Serilog.

[gthvidsten]

@sungam3r Good find! So it seems this is an issue with ASP,NET Core outputting messages to the console regardless of logging, which basically explains everything. It also means this is not a Serilog issue at all, so I’ll close this issue and see if anybody has reported this for aspnet/AspNetCore (and report it myself if not).

Thanks for the assistance!

[sungam3r]

I missed a bit -https://github.com/aspnet/AspNetCore/blob/master/src/Hosting/Hosting/src/WebHostExtensions.cs#L116