ASP.NET Core 启动消息日志

Question

I have an ASP.NET Core 3.1 app, which was upgraded from ASP.NET Core 2.0. We would like to get the old startup messages ("Now listening on: http://localhost:5000", etc) to log through the configured structured logging options. This works out of the box with new 3.1 projects, but I cannot figure out how to enable it in an existing project that does not use the ConfigureWebHostDefaults() method at startup. For example, this logs startup through structured logging:

public static void Main(string[] args)
{
    CreateHostBuilder(args).Build().Run();
}

public static IHostBuilder CreateHostBuilder(string[] args) =>
    Host.CreateDefaultBuilder(args)
        .ConfigureWebHostDefaults(webBuilder =>
        {
            webBuilder.UseStartup<Startup>();
        });

But this doesn't:

public static void Main(string[] args)
{
    new WebHostBuilder()
        .UseKestrel()
        .ConfigureLogging((hostingContext, logging) =>
        {
            logging.AddDebug();
            logging.AddConsole();
        })
        .UseStartup<Startup>()
        .Build()
        .Run();
}

I found this question:

What is the difference between ConfigureWebHostDefaults and ConfigureWebHost methods?

and scanned through the code linked there, but I'm coming up blank. What's the magic incantation to connect Kestrel to the logging infrastructure?

Answer 1

In the end, we just needed to fully switch over to the new host builder ( CreateHostBuilder vs the older CreateWebHostBuilder ). We had tried it before, but when we added our custom logging provider in ConfigureLogging we ended up with duplicated log messages, so we rolled back to the old way without fully understanding the difference. The missing bit was calling ClearProviders() . Before, we had:

public static void Main(string[] args)
{
    CreateWebHostBuilder(args).Build().Run();
}

public static IWebHostBuilder CreateWebHostBuilder(string[] args) => WebHost.CreateDefaultBuilder(args)
    .UseKestrel()
    .ConfigureAppConfiguration((context, config) => { ... }))
    .ConfigureLogging((hostingContext, logging) =>
    {
        logging.AddConfiguration(hostingContext.Configuration.GetSection("Logging"));

        logging.AddProvider(new CustomLoggerProvider());
        logging.AddDebug();
    })
    .UseStartup<Startup>();

And now:

public static void Main(string[] args)
{
     CreateHostBuilder(args).Build().Run();
}

public static IHostBuilder CreateHostBuilder(string[] args) => Host.CreateDefaultBuilder(args)
    .ConfigureAppConfiguration((hostingContext, config) => { ... } ))
    .ConfigureLogging((hostBuilder, logging) =>
    {                
        logging.ClearProviders();

        logging.AddConfiguration(hostBuilder.Configuration.GetSection("Logging"));

        logging.AddProvider(new CustomLoggerProvider());
        logging.AddDebug();
    })
    .ConfigureWebHostDefaults(webBuilder =>
    {
        webBuilder.UseStartup<Startup>();
    });

Now Kestrel nicely logs it's status messages to the preferred logger along with everything else.