Duende IdentityServer uses the standard logging facilities provided by ASP.NET Core. You don’t need to do any extra configuration.

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 internal 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…

In production, logging might produce too much data. It is recommended you either turn it off, or default to the Warning level. Have a look at events for more high-level production instrumentation.

Setup for Serilog

We personally like Serilog and the Serilog.AspNetCore package a lot. Give it a try:

Activity.DefaultIdFormat = ActivityIdFormat.W3C;

Log.Logger = new LoggerConfiguration()
    .MinimumLevel.Override("Microsoft", LogEventLevel.Warning)
    .MinimumLevel.Override("Microsoft.Hosting.Lifetime", LogEventLevel.Information)
    .MinimumLevel.Override("System", LogEventLevel.Warning)
    .MinimumLevel.Override("Microsoft.AspNetCore.Authentication", LogEventLevel.Information)
    .WriteTo.Console(outputTemplate: "[{Timestamp:HH:mm:ss} {Level}] {SourceContext}{NewLine}{Message:lj}{NewLine}{Exception}{NewLine}", theme: AnsiConsoleTheme.Code)