Setting up Serilog in ASP.NET Core

WHAT TO LOG

It is not enough to log errors in order to use them for troubleshooting purposes. It is also useful to log successful requests so we can have a clear idea of how users work with the application .

Logs are also useful to detect  mistakes that users make, as well as for security purposes. Writing good logs about a user’s activity can alert us about malicious activity or any other kind of problems that we didn’t detect .

Why use Serilog ?

Serilog provides basic diagnostic logging not only to the console, files, Amazon, Azure, but more ,it’s easy to integrate and to use in a few steps .

This article will demonstrate the console and file sinks. It is easy as 1, 2, 3 to set up with appsettings configurations.

Steps : 

 

First thing that we are going to do is to create a new empty solution (Web Api )

Now we need to use the package manager to install some extensions as in pictures below or you can use the command :

Serilog.AspNetCore package

 

Logger initialization in Program.cs :

To start working with Serielog we need to initilize it first in the program.cs  .
You can copy replace your code with the below code :

public static void Main(string[] args)
       {
           var configuration = new ConfigurationBuilder()
           .AddJsonFile("appsettings.json")
           .Build();

           Log.Logger = new LoggerConfiguration()
               .ReadFrom.Configuration(configuration).WriteTo.Console().CreateLogger();

           try
           {
               Log.Information("Application startinng up");
               CreateHostBuilder(args).Build().Run();
           }
           catch (Exception ex)
           {

               Log.Fatal(ex, "The application failed to start correctly");
           }
           finally
           {
               Log.CloseAndFlush();

           }



       }

Also , we need to add : .UseSerilog() inside the CreateHostBuilder :

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

 

Next , inside the Startup.cs we need to add : app.UseSerilogRequestLogging();

 

Now if we run our solution , we should see inside the console a message saying : Application startinng up ,

if you remember we added a line of code that will fire when the application start :

Log.Information("Application startinng up");

 

 

Cleaning up The default logger :

There are a few more changes that we are going to do and now inside the appsettings.json .

Serilog completely replaces the logging implementation on .NET Core,it will not work together  but it will replace the default implementation . The benefit of this is that you’re not running two different logging frameworks with tricky edge cases where they overlap in functionality.

{
  "AllowedHosts": "*",
  "Serilog": {
    "Using": [],
    "MinimumLevel": {
      "Default": "Information",
      "Override": {
        "Microsoft": "Warning",
        "System": "Warning"
      }
    },
    "Enrich": [ "FromLogContext", "WithMachineName", "WithProcessId", "WithThreadId" ],
    "WriteTo": [
      { "Name": "Console" },
      {
        "Name": "File",
        "Args": {
          "path": "Logs/log.txt",
          "rollingInterval": "Day",
          "outputTemplate": "{Timestamp:G} {Message}{NewLine:1}{Exception:1}"
        }
      },
      {
        "Name": "File",
        "Args": {
          "path": "Logs/log.json",
          "rollingInterval": "Day",
          "formatter": "Serilog.Formatting.Json.JsonFormatter, Serilog"
        }
      }
   
    ]
  }
}

The “Name” key here specifies the sink desired. To write to multiple sinks, add another object to the “WriteTo” array , in our case we want to create files inside a logs folder and each day we want to create a new different file that contain the date time .

The MinimumLevel configuration object provides for one of the log event levels to be specified as the minimum.

If you see ,we have “path“: “Logs/log.txt”, where we define where we want our file to be written to and stored .

rollingInterval here mean that we want to create a new file per day .

as you can see inside write to , we defined to object , one that will write to a text file and another one that’s going to write inside a json file .

Now let’s run our solution :

 

As you can see there is a new Folder created : Logs , that contain a json file and a txt file .
let explore those 2 files :

{"Timestamp":"2020-09-13T15:04:23.3942682+01:00","Level":"Information","MessageTemplate":"Application startinng up"}
{"Timestamp":"2020-09-13T15:04:25.9319025+01:00","Level":"Information","MessageTemplate":"Getting WeatherForecast details","Properties":{"ActionId":"9612d1c8-4c4e-44b7-b7fd-374fe905687c","ActionName":"SerielogDemoDay.Controllers.WeatherForecastController.Get (SerielogDemoDay)","RequestId":"0HM2NTNM09MCA:00000001","RequestPath":"/weatherforecast","SpanId":"|b35b87a8-42a0adeaed09085c.","TraceId":"b35b87a8-42a0adeaed09085c","ParentId":""}}
{"Timestamp":"2020-09-13T15:04:25.9642904+01:00","Level":"Information","MessageTemplate":"HTTP {RequestMethod} {RequestPath} responded {StatusCode} in {Elapsed:0.0000} ms","Properties":{"RequestMethod":"GET","RequestPath":"/weatherforecast","StatusCode":200,"Elapsed":134.7792,"SourceContext":"Serilog.AspNetCore.RequestLoggingMiddleware","RequestId":"0HM2NTNM09MCA:00000001","SpanId":"|b35b87a8-42a0adeaed09085c.","TraceId":"b35b87a8-42a0adeaed09085c","ParentId":""},"Renderings":{"Elapsed":[{"Format":"0.0000","Rendering":"134.7792"}]}}

As You can see the json file is very detailed file that contain all the event that happened .

while the txt file below , contain the actions with date time .

09/13/2020 15:04:23 Application startinng up
09/13/2020 15:04:25 Getting WeatherForecast details
09/13/2020 15:04:25 HTTP "GET" "/weatherforecast" responded 200 in 134.7792 ms

and now you can log anywhere inside your application by just using :

Log.Debug("debug test!");
Log.Information("Informations here.....!");
Log.Error("Error here ....!");

 

Link to demo project .