Serilog.Sinks.File.Header 1.0.0-dev

Serilog.Sinks.File.Header

A FileLifecycleHooks-based plugin for the Serilog File Sink that writes a configurable header at the start of each log file.

Getting started

FileLifecycleHooks is a new Serilog File Sink mechanism that allows hooking into log file lifecycle events, and allows scenarios such as wrapping the Serilog output stream in another stream.

This new mechanism is so far only available in the the dev Serilog packages, so note that if you already have a production version of the Serilog.Sinks.File package installed, you will need to switch it out for the latest dev version.

To get started, install the latest Serilog.Sinks.File.Header dev package from NuGet:

Install-Package Serilog.Sinks.File.Header -Version 1.0.0-dev

To enable writing a header, use one of the new LoggerSinkConfiguration extensions that has a FileLifecycleHooks argument, and create a new HeaderWriter:

Log.Logger = new LoggerConfiguration()
    .WriteTo.File("log.txt", hooks: new HeaderWriter("Timestamp,Level,Message"))
    .CreateLogger();

Note this also works if you enable rolling log files.

Instead of writing a static string, you can instead provide a factory method that resolves the header at runtime:

Func<string> headerFactory = () => $"My dynamic header {DateTime.UtcNow}";

Log.Logger = new LoggerConfiguration()
    .WriteTo.File("log.txt", hooks: new HeaderWriter(headerFactory))
    .CreateLogger();

JSON appsettings.json configuration

It's also possible to enable log file headers when configuring Serilog from a configuration file using Serilog.Settings.Configuration. To do this, you will first need to create a public static class that can provide the configuration system with a configured instance of HeaderWriter:

using Serilog.Sinks.File.Header;

namespace MyApp.Logging
{
    public class SerilogHooks
    {
        public static HeaderWriter MyHeaderWriter => new HeaderWriter("Timestamp,Level,Message");
    }
}

The hooks argument in Your appsettings.json file should be configured as follows:

{
  "Serilog": {
    "WriteTo": [
      {
        "Name": "File",
        "Args": {
          "path": "log.gz",
          "hooks": "MyApp.Logging.SerilogHooks::MyHeaderWriter, MyApp"
        }
      }
    ]
  }
}

To break this down a bit, what you are doing is specifying the fully qualified type name of the static class that provides your HeaderWriter, using Serilog.Settings.Configuration's special :: syntax to point to the MyHeaderWriter member.

Sample application

A basic console app is provides as a sample.