Logging

IdentityServer uses the standard logging facilities provided by ASP.NET Core. The Microsoft documentation has a good intro and a description of the built-in logging providers.

We are roughly following the Microsoft guidelines for usage of log levels:

  • Trace For information that is valuable only to a developer troubleshooting an issue. These messages may contain sensitive application data like tokens and should not be enabled in a production environment.
  • Debug For following the interal flow and understanding why certain decisions are made. Has short-term usefulness during development and debugging.
  • Information For tracking the general flow of the application. These logs typically have some long-term value.
  • Warning For abnormal or unexpected events in the application flow. These may include errors or other conditions that do not cause the application to stop, but which may need to be investigated.
  • Error For errors and exceptions that cannot be handled. Examples: failed validation of a protocol request.
  • Critical For failures that require immediate attention. Examples: missing store implementation, invalid key material...

Setup

We personally like Serilog a lot. Give it a try.

You want to setup logging as early as possible in your application host, e.g. in the constructor of your startup class, e.g:

public class Startup
{
    public Startup(ILoggerFactory loggerFactory, IHostingEnvironment environment)
    {
        var serilog = new LoggerConfiguration()
            .MinimumLevel.Verbose()
            .Enrich.FromLogContext()
            .WriteTo.File(@"identityserver4_log.txt");

        if (environment.IsDevelopment())
        {
            serilog.WriteTo.LiterateConsole(outputTemplate: "[{Timestamp:HH:mm:ss} {Level}] {SourceContext}{NewLine}{Message}{NewLine}{Exception}{NewLine}");
        }

        loggerFactory
            .WithFilter(new FilterLoggerSettings
            {
                { "IdentityServer", LogLevel.Debug },
                { "Microsoft", LogLevel.Information },
                { "System", LogLevel.Error },
            })
            .AddSerilog(serilog.CreateLogger());
    }
}