A FileLifecycleHooks-based plugin for the Serilog File Sink that works with rolling log files, archiving completed log files before they are deleted by Serilog's retention mechanism.

The following archive methods are supported:

• Compress logs in the same directory (using GZip compression)
• Copying logs to another directory
• Compress logs (using GZip compression) and write them to another directory

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

Install-Package Serilog.Sinks.File.Archive -Version 1.0.1

To enable archiving, use one of the new LoggerSinkConfiguration extensions that has a FileLifecycleHooks argument, and create a new ArchiveHooks. For example, to write GZip compressed logs to another directory (the directory will be created if it doesn't already exist):

Log.Logger = new LoggerConfiguration()
    .WriteTo.File("my-app.log", hooks: new ArchiveHooks(CompressionLevel.Fastest, "C:\\My\\Archive\\Path"))
    .CreateLogger();

Or to copy logs as-is to another directory:

Log.Logger = new LoggerConfiguration()
    .WriteTo.File("my-app.log", hooks: new ArchiveHooks(CompressionLevel.NoCompression, "C:\\My\\Archive\\Path"))
    .CreateLogger();

Or to write GZip compressed logs to the same directory the logs are written to:

Log.Logger = new LoggerConfiguration()
    .WriteTo.File("my-app.log", hooks: new ArchiveHooks(CompressionLevel.Fastest))
    .CreateLogger();

Note that archival only works with rolling log files, as files are only deleted by Serilog's rolling file retention mechanism.

As is standard with Serilog, it's important to call Log.CloseAndFlush(); before your application ends.

The targetDirectory constructor parameter supports replacement of tokens at runtime.

Tokens take the form {Name:FormatString}, where Name is the name of a supported token, and FormatString defines how the token value should be formatted.

At present, 2 tokens are supported, UtcDate and Date. These use standard .NET date format strings to insert components of the current date/time into the path. For example, you may wish to organise archived files into folders based on the current year and month:

new ArchiveHooks(CompressionLevel.Fastest, "C:\\Archive\\{UtcDate:yyyy}\\{UtcDate:MM}")

It's also possible to enable archival 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 ArchiveHooks:

using Serilog.Sinks.File.Archive;

namespace MyApp.Logging
{
    public class SerilogHooks
    {
        public static ArchiveHooks MyArchiveHooks => new ArchiveHooks(CompressionLevel.Fastest, "C:\\My\\Archive\\Path");
    }
}

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

{
  "Serilog": {
    "WriteTo": [
      {
        "Name": "File",
        "Args": {
          "path": "my-app.log",
          "fileSizeLimitBytes": 10485760,
          "rollOnFileSizeLimit": true,
          "retainedFileCountLimit": 5,
          "hooks": "MyApp.Logging.SerilogHooks::MyArchiveHooks, 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 ArchiveHooks, using Serilog.Settings.Configuration's special :: syntax to point to the MyArchiveHooks member.

FileLifecycleHooks is a Serilog File Sink mechanism that allows hooking into log file lifecycle events, enabling scenarios such as wrapping the Serilog output stream in another stream, or capturing files before they are deleted by Serilog's retention mechanism.

Other available hooks include:

• serilog-sinks-file-header: writes a header to the start of each log file
• serilog-sinks-file-gzip: compresses logs as they are written, using streaming GZIP compression