IdentityServer has two logging related features. Development-time logging and production-time events (see here).

Development-time logging produces a quite extensive output and is mostly useful for developers that customize IdentityServer. Logging might store sensitive data like passwords and thus is typically not suitable for production use.

IdentityServer uses LibLog for logging. Liblog picks up any of the following logging libraries automatically:

There is no IdentityServer3 specific configuration required - you just need to configure one of the above logging frameworks in your host.

Warning: LibLog will pick the first library in the above order and will discard the others. So if you have a reference to SeriLog for example and you’re trying to configure Log4net it will not work.

Configuring Diagnostics

The LoggingOptions class has the following settings:

Example: Using Serilog to log to System.Diagnostics tracing

The following example wires up Serilog to log to the diagnostics trace (put that e.g. in Startup or in your hosting code). Note: Serilog provides various logging sinks as separate packages, so you may need to install the Serilog.Sinks.Trace package to get WriteTo.Trace() to work as expected.

Log.Logger = new LoggerConfiguration()

Add the following snippet to your configuration file to funnel all logging messages to a simple text file. We use Baretail for viewing the log files.

  <trace autoflush="true"
      <add name="myListener"
           initializeData="Trace.log" />
      <remove name="Default" />

Note: If you use this method you need to ensure that the account running the application pool has write access to the directory containing the log file. If you don’t specify a path, this will be the application directory, which is not recommended for production scenarios. For production log to a file outside the application directory.

Example: Log to the console

Logging to the console gives you a friction free and immediate insight into the internals of IdentityServer. Serilog has a nice colored console logging sink called Serilog.Sinks.Literate. Wire it up like this:

Log.Logger = new LoggerConfiguration()

Instrumenting your own code

You can also use the logging system in your own extensibility code.

Add a static ILog instance to your class

private readonly static ILog Logger = LogProvider.For<MyClass>();

Log your messages using the logger

Logger.Debug("Getting claims for identity token");

Using your own Logging Infrastructure

You may have an existing logging infrastructure in place and want IdentityServer logging to use that. The recommended approach for this is to write a custom sink using one of the supported logging frameworks (our favourite is Serilog). You can find a sample here.

See here for a post about logging and eventing.

Suppressing all logging output

(added in v2.5)

For certain scenarios (e.g. production) you want to make sure that no logging output is produced. For this you can configure a no-op logger (typically done in Startup or in the hosting code):

LogProvider.SetCurrentLogProvider(new NoopLogProvider());