asp.net-coreserilogserilog-aspnetcoreserilog-sinks-seq

Toggle Serilog sink at runtime

I'm using code-based Serilog config (not appsettings). I want to toggle a sink at runtime; specifically Seq, but others too.

I know of the WriteTo.Conditional feature:

var isFooEnabled = true;
var isSeqEnabled = true;

services.AddSerilog((services, config) => config
  // ...
  .WriteTo.Console()
  .WriteTo.Conditional(x => isFooEnabled, x => x.Foo())
  .WriteTo.Conditional(x => isSeqEnabled, x => x.Seq(SEQ_URL))
);

But that code is located in the composition root (i.e. it's run during app start). I need to toggle a sink much later.

I'd probably need to resolve some service which can make the toggling decision. But how would I connect that to the above config code, at runtime? I couldn't find a hook for such functionality.

(Please note that switching to the appsettings approach is not feasible.)

Solution

  • I found a solution, based on this and this.

    Add a type that encapsulates LoggingLevelSwitch:

    public class SinkSwitch
{

  private readonly LoggingLevelSwitch _switch;
  private LogEventLevel _level;

  public SinkSwitch(LogEventLevel level)
  {
    if (!Enum.IsDefined(level)) throw new ArgumentOutOfRangeException(nameof(level));
    _level = level;
    _switch = new LoggingLevelSwitch(level);
  }

  public LoggingLevelSwitch Switch => _switch;

  public bool IsEnabled => _switch.MinimumLevel != LevelAlias.Off;

  public void Toggle()
  {
    _switch.MinimumLevel = _switch.MinimumLevel == LevelAlias.Off
      ? _level
      : LevelAlias.Off;
  }

  public void Change(LogEventLevel level)
  {
    if (!Enum.IsDefined(level)) throw new ArgumentOutOfRangeException(nameof(level));
    _level = level;
    _switch.MinimumLevel = level;
  }

}

    During startup, before configuring Serilog, create the switch and store it as a singleton:

    var sinkSwitch = new SinkSwitch(LogEventLevel.Information);
services.AddSingleton(sinkSwitch);

    Then configure Serilog:

    services.AddSerilog((services, config) => config
  // ...
  .WriteTo.Console(levelSwitch:sinkSwitch.Switch)
  .WriteTo.Seq(SEQ_URL, controlLevelSwitch:sinkSwitch.Switch)
);

    Notes: