Serilog console sink that logs exception message without stacktrace

Question

Some of Serilog's standard template properties can be customised, e.g. {Timestamp:HH:mm:ss}, {Level:u3} and {Message:lj}. Not so for {Exception}, which prints both message and stack trace, on multiple lines.

For the human-readable console sink, a stack trace adds significant noise and friction, especially when tailing a remote docker container which is already ugly (no colour, for example). If I need the stack trace, I would consult a durable sink, e.g. file, Seq.

How can I log just the exception message to the console sink?

(I'm aware of Serilog.Expressions, but for something so simple I hope there's a solution without another dependency.)

Answer 1

As per a comment on the repo, here's a solution using a custom enricher.

Create the enricher ExceptionMessageEnricher.cs:

using Serilog.Core;
using Serilog.Events;

namespace Serilog.Enrichers;

public sealed class ExceptionMessageEnricher : ILogEventEnricher
{
  public const string PROPERTY_NAME = "ExceptionMessage";

  public void Enrich(LogEvent logEvent, ILogEventPropertyFactory propertyFactory)
  {
    ArgumentNullException.ThrowIfNull(logEvent, nameof(logEvent));
    ArgumentNullException.ThrowIfNull(propertyFactory, nameof(propertyFactory));

    if (logEvent.Exception == null) return;

    var property = propertyFactory.CreateProperty(PROPERTY_NAME, $"\"{logEvent.Exception.Message}\"");
    logEvent.AddPropertyIfAbsent(property);
  }

}

Then use it in the Serilog config:

var outputTemplate = "[{Timestamp:HH:mm:ss} {Level:u3}] {Message:lj} {ExceptionMessage}{NewLine}";

services.AddSerilog((services, config) => config
  // ...
  .WriteTo.Logger(x => x
    .Enrich.With<ExceptionMessageEnricher>()
    .WriteTo.Console(outputTemplate:outputTemplate)
  )
);

A rendered message would look something like this:

[13:04:44 ERR] Something bad happened "The exception message"

Notes:

• The custom enricher adds an ExceptionMessage property, which is then referenced in the log template
• The ExceptionMessage property is not needed in durable sinks (e.g. file, Seq) as they receive the full exception anyway; thus the console sink and custom enricher are defined in a sub-logger - I'm unaware whether there are perf considerations, but I suspect it should be fine
• If needed, the console sink can be wrapped in an async sink

An alternative approach, using Serilog.Expressions: {Inspect(@x).Message}.