Loki Logging Provider

Send logs directly to Grafana Loki from your .NET application. The Loki Logging Provider is a simple library that plugs into the logging framework provided in .NET.

For more information about logging, please checkout Logging in .NET and Logging in .NET Core and ASP.NET Core.

Warning: This package has not been optimized for high performance logging.

Usage

Step 1. Install the Package

The Loki logging provider is available from Nuget.org. Add it to your project with the command;

dotnet add package LokiLoggingProvider --version <version>

Step 2. Add the Logging Provider

For host based apps using the WebApplicationBuilder introduced in .NET 6, add the Loki logging provider by calling the AddLoki() extension method on the WebApplicationBuilder.Logging builder instance.

WebApplicationBuilder builder = WebApplication.CreateBuilder(args);
builder.Logging.AddLoki();

For older host based apps, add the Loki logging provider by calling the AddLoki() extension method on the ILoggingBuilder instance when configuring your host.

using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;

public class Program
{
    public static void Main(string[] args)
    {
        CreateHostBuilder(args).Build().Run();
    }

    public static IHostBuilder CreateHostBuilder(string[] args)
    {
        return Host.CreateDefaultBuilder(args)
            .ConfigureLogging(logBuilder =>
            {
                logBuilder.AddLoki();
            })
            .ConfigureWebHostDefaults(webBuilder =>
            {
                webBuilder.UseStartup<Startup>();
            });
    }
}

For non-host based apps, add the Loki logging provider by calling the AddLoki() extension method when creating your ILoggerFactory.

using Microsoft.Extensions.Logging;

public class Program
{
    public static void Main()
    {
        using ILoggerFactory loggerFactory = LoggerFactory.Create(builder =>
        {
            builder.AddLoki();
        });

        ILogger<Program> logger = loggerFactory.CreateLogger<Program>();

        logger.LogInformation("Hello from my Console App!");
    }
}

Step 3. Configure Logging

By default, the Loki logging provider does nothing. You must specify the type of push client (Grpc or Http) to use before any logs will be sent to Loki. Configure the Loki logging provider by modifying appsettings.json or its variants. An example is below.

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft": "Warning",
      "Microsoft.Hosting.Lifetime": "Information"
    },
    "Loki": {
      "LogLevel": {
        "Default": "Information",
        "Microsoft": "Warning",
        "Microsoft.Hosting.Lifetime": "Information"
      },
      "Client": "Grpc",
      "Grpc": {
        "Address": "http://localhost:9095"
      },
      "StaticLabels": {
        "JobName": "Example.WebApp"
      }
    }
  }
}

For a complete list of all the options you can configure and their defaults, please checkout the LokiLoggerOptions class and its related classes. The Loki section in appsettings.json basically binds to this class.

Alternatively, you can configure the Loki logging provider by passing an Action delegate that configures an instance of LokiLoggerOptions to the AddLoki() extension method.

Examples

There are two example projects that use the Loki logging provider which you can use as a reference.

• Example.ConsoleApp
• Example.WebApp

There is also a docker-compose.yml file which you can use to help spin up an instance of Grafana and Loki in Docker for local development purposes.