Serilog Logging in ASP.Net core

Author : MD TAREQ HASSAN

Installing packages

Install-Package Serilog.AspNetCore

Serilog.AspNetCore already has references to the following packages:

Install-Package Serilog.Settings.Configuration
Install-Package Serilog.Sinks.Console
Install-Package Serilog.Sinks.File
Install-Package Serilog.Formatting.Compact

Extra packages (if you want/need):

Install-Package Serilog.Sinks.Async

Install-Package Serilog.Enrichers.Environment
Install-Package Serilog.Enrichers.Process
Install-Package Serilog.Enrichers.Thread

appsettings json

appsettings.Development.json
appsettings.Production.json

{
  "Serilog": {
    "MinimumLevel": {
      "Default": "Warning"
    },
    "Enrich": [
      "FromLogContext"
    ],
    "Properties": {
      "Application": "HovermindApp"
    },
    "WriteTo": [
      {
        "Name": "Console",
        "Args": {
          "outputTemplate": "[{Timestamp:HH:mm:ss} {Level:u3}] {Message:lj} <s:{SourceContext}>{NewLine}{Exception}",
          "theme": "Serilog.Sinks.SystemConsole.Themes.SystemConsoleTheme::Literate, Serilog.Sinks.Console"
        }
      },
      {
        "Name": "Async",
        "Args": {
          "configure": [
            {
              "Name": "File",
              "Args": {
                "formatter": "Serilog.Formatting.Compact.CompactJsonFormatter, Serilog.Formatting.Compact",
                "path": "D:/home/LogFiles/Application/HovermindApp.ndjson",
                "shared": "true",
                "fileSizeLimitBytes": "1000000",
                "rollOnFileSizeLimit": true,
                "flushToDiskInterval": "1"
              }
            }
          ]
        }
      }
    ]
  }
}

Logger initialization in Program class

all settings are in appsettings.json & can be overriden by fluent api (some settings are not possible by appsettings.json, those seeting are set by fluent api)
try/catch used to log application start-up exceptions
Plugging into ASP.NET Core with UseSerilog()
Important: Serilog in ASP.NET Core 3 plugs into the generic host and not webBuilder
https://github.com/serilog/serilog-aspnetcore

Program.cs

public class Program
{
	public static IConfiguration Configuration { get; } = new ConfigurationBuilder()
		.SetBasePath(Directory.GetCurrentDirectory())
		.AddJsonFile("appsettings.json", optional: false, reloadOnChange: true)
		.AddJsonFile($"appsettings.{Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT") ?? "Production"}.json", optional: true)
		.AddEnvironmentVariables()
		.Build();

	public static int Main(string[] args)
	{
		Log.Logger = new LoggerConfiguration().ReadFrom.Configuration(Configuration).CreateLogger();

		try
		{
			Log.Information("Getting the motors running...");

			CreateHostBuilder(args).Build().Run();

			return 0;
		}
		catch (Exception ex)
		{
			Log.Fatal(ex, "Host terminated unexpectedly");
			return 1;
		}
		finally
		{
			Log.CloseAndFlush();
		}
	}

	public static IHostBuilder CreateHostBuilder(string[] args){
	
		// Serilog in ASP.NET Core 3 plugs into the generic host and not webBuilder
		
		return Host.CreateDefaultBuilder(args).ConfigureWebHostDefaults(webBuilder => {
				webBuilder.UseStartup<Startup>();
			})
			.UseSerilog(); // <- Plug Serilog into the pipeline;
	}
}

Another way:

public class Program
{


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

	public static IHostBuilder CreateHostBuilder(string[] args){
	
		// Serilog in ASP.NET Core 3 plugs into the generic host and not webBuilder
		return Host.CreateDefaultBuilder(args).ConfigureWebHostDefaults(webBuilder => {
			webBuilder.UseStartup<Startup>();
		})
        .UseSerilog((context, config) =>
        {
            config.ReadFrom.Configuration(context.Configuration);
        })
	}
}

Logging section in appsettings json

Since Serilog is plugged into ASP.Net core, all logging will be done by Serilog
Even if logging is done by ILogger<T> of ASP.Net core (by DI), logging will be done by Serilog
Logging section in appsettings.json will not be used by Serilog, so remove Logging section from all appsettings.json (default, Development, Production etc.)

Logging in Controller

Using Dependency Injection

HomeController.cs

using Serilog;

public class HomeController : Controller
{
	private ILogger<HomeController> _logger;
	
    private static IFooService _fs;
    
    public HomeController(ILogger<HomeController> logger, IFooService fs, ...)
    {
		_logger = logger;
        _fs = fs;
		
		// ... ... ...
    }
    
    public IActionResult Index()
    {

        var foo = new Foo { Id = 2, FooName = "FooTwo" };
		
        _logger.Information("Object: {@FooMan}", foo); // @ : destructuring operator
        
        return View();
    }
}

Using static Log

HomeController.cs

using Serilog;

public class HomeController : Controller
{
    private static IFooService _fs;
    
    public HomeController(IFooService fs)
    {
        _fs = fs;
    }
    
    public IActionResult Index()
    {

        var foo = new Foo { Id = 2, FooName = "FooTwo" };
		
        Log.Information("Object: {@FooMan}", foo); // @ : destructuring operator
        
        return View();
    }
}

seq sink

seq in docker: Running seq in docker

seq sink package installation

Install-Package Serilog.Sinks.Seq

configuration for seq in appsettings.json

{
  "Serilog": {
    "MinimumLevel": {
      "Default": "Debug",
      "Override": {
        "Microsoft": "Warning",
        "System": "Warning"
      }
    },
    "Enrich": [
      "FromLogContext"
    ],
    "Properties": {
      "Application": "HoverApp"
    },
    "WriteTo": [
      // ... ... ...
      {
        "Name": "Seq",
        "Args": {
          "serverUrl": "http://localhost:5341",
          "compact": true
        }
      }
    ]
  }
}

Request logging

Serilog.AspNetCore includes middleware for smarter HTTP request logging ( The default request logging implemented by ASP.NET Core is noisy, with multiple events emitted per request)
UseSerilogRequestLogging() => plugs request logging middleware
It’s important that the UseSerilogRequestLogging() call appears before handlers such as MVC
to exclude noisy handlers from logging, such as UseStaticFiles(), by placing UseSerilogRequestLogging() after them
https://github.com/serilog/serilog-aspnetcore#request-logging

To enable the middleware, first change the minimum level for Microsoft.AspNetCore to Warning

{
  "Serilog": {
    "MinimumLevel": {
      "Default": "Debug",
      "Override": {
        "Microsoft.AspNetCore": "Warning"
      }
    },
    // ... ... ...
}

In Startup.cs, add the middleware with UseSerilogRequestLogging()

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
	if (env.IsDevelopment())
	{
		app.UseDeveloperExceptionPage();
	}
	else
	{
		app.UseExceptionHandler("/Home/Error");
	}

	app.UseSerilogRequestLogging(); // <-- Add this line

	// Other app configuration
	// ... ... ...
}

options callback on UseSerilogRequestLogging() (modify message template, events, properties etc.)

// ... ... ...

app.UseSerilogRequestLogging(options =>
{
    // Customize the message template
    options.MessageTemplate = "Handled {RequestPath}";
    
    // Emit debug-level events instead of the defaults
    options.GetLevel = (httpContext, elapsed, ex) => LogEventLevel.Debug;
    
    // Attach additional properties to the request completion event
    options.EnrichDiagnosticContext = (diagnosticContext, httpContext) =>
    {
        diagnosticContext.Set("RequestHost", httpContext.Request.Host.Value);
        diagnosticContext.Set("RequestScheme", httpContext.Request.Scheme);
    };
});

// ... ... ...

Response logging

Logging to Azure Blob Storage

/aspnet-core/logging#logging-to-azure-blob-storage-using-serilog