This repository contains plugins for popular .NET logging frameworks that integrate with Amazon Web Services. The plugins use the Amazon CloudWatch Logs service to write log data to a configured log group. The logs can be viewed and searched using the AWS CloudWatch Console.

For a history of releases view the release change log

These packages batch logging messages in a queue and send messages to CloudWatch Logs using a background thread. The use of the background thread means that the messages are not guaranteed to be delivered when used in AWS Lambda. The reason is because the background thread will be frozen once a Lambda event is processed and may not ever be unfrozen if more Lambda events are not received for some time.

When using Lambda it is recommended to use either the ILambdaContext.Logger.LogLine or the Amazon.Lambda.Logging.AspNetCore package.

1. NLog
2. Apache log4net
3. ASP.NET Core Logging

• NuGet Package: AWS.Logger.Nlog

NLog uses targets that can be configured to receive log messages. Targets can be configured either through a config file or through code. The default config file that NLog will automatically search for is NLog.config. Here is an example config file that configures the AWS Region and the CloudWatch Logs log group.

<?xml version="1.0" encoding="utf-8" ?>
<nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      throwExceptions="true">
  <targets>
    <target name="aws" type="AWSTarget" logGroup="NLog.ConfigExample" region="us-east-1"/>
  </targets>
  <rules>
    <logger name="*" minlevel="Info" writeTo="aws" />
  </rules>
</nlog>

The AWS credentials will be found using the standard AWS SDK for .NET credentials search path. In this case it will look for a profile named default, search for environment variables or search for an instance profile on an EC2 instance. To use a specific AWS credential profile use the profile attribute on the target.

Here is an example of performing the same configuration via code.

var config = new LoggingConfiguration();

var awsTarget = new AWSTarget()
{
    LogGroup = "NLog.ProgrammaticConfigurationExample",
    Region = "us-east-1"
};
config.AddTarget("aws", awsTarget);

config.LoggingRules.Add(new LoggingRule("*", LogLevel.Debug, awsTarget));

LogManager.Configuration = config;

Checkout the NLog samples for examples on how you can use AWS and NLog together.

• NuGet Package: AWS.Logger.Log4net

Log4net configures appenders to receive log messages. Appenders can be configured either through a config file or through code. To use a config file add a file to your project. The file can be named anything but for this example call it log4net.config. Make sure that Copy to Output Directory is set to copy. Here is an example config file setting the CloudWatch Log log group and the AWS Region.

<?xml version="1.0" encoding="utf-8" ?>
<log4net>
  <appender name="AWS" type="AWS.Logger.Log4net.AWSAppender,AWS.Logger.Log4net">

    <LogGroup>Log4net.ConfigExample</LogGroup>
    <Region>us-east-1</Region>
    
    <layout type="log4net.Layout.PatternLayout">
      <conversionPattern value="%-4timestamp [%thread] %-5level %logger %ndc - %message%newline" />
    </layout>
  </appender>

  <root>
    <level value="DEBUG" />
    <appender-ref ref="AWS" />
  </root>
</log4net>

The AWS credentials will be found using the standard AWS SDK for .NET credentials search path. In this case it will look for a profile named default, search for environment variables or search for an instance profile on an EC2 instance. To use a specific AWS credential profile add a Profile under the appender node.

Add the following code during the startup of the application to have log4net read the configuration file.

// log4net is configured in the log4net.config file which adds the AWS appender.
XmlConfigurator.Configure(new System.IO.FileInfo("log4net.config"));

Here is an example of performing the same configuration via code.

static void ConfigureLog4net()
{
    Hierarchy hierarchy = (Hierarchy)LogManager.GetRepository();
    PatternLayout patternLayout = new PatternLayout();

    patternLayout.ConversionPattern = "%-4timestamp [%thread] %-5level %logger %ndc - %message%newline";
    patternLayout.ActivateOptions();

    AWSAppender appender = new AWSAppender();
    appender.Layout = patternLayout;

    // Set log group and region. Assume credentials will be found using the default profile or IAM credentials.
    appender.LogGroup = "Log4net.ProgrammaticConfigurationExample";
    appender.Region = "us-east-1";

    appender.ActivateOptions();
    hierarchy.Root.AddAppender(appender);

    hierarchy.Root.Level = Level.All;
    hierarchy.Configured = true;
}

Checkout the Log4net samples for examples of how you can use AWS and log4net together.

• NuGet Package: AWS.Logger.AspNetCore

ASP.NET Core introduced a new logging framework that has providers configured to send logs to destinations. The AWS.Logger.AspNetCore NuGet package provides a log provider which adds CloudWatch Logs as a destination for the logs.

The WebSample in this repository demonstrates how to configure this provider.

The configuration is setup in the appsettings.json file

"AWS.Logging": {
  "Region": "us-east-1",
  "LogGroup": "AspNetCore.WebSample",
  "LogLevel": {
    "Default": "Debug",
    "System": "Information",
    "Microsoft": "Information"
  }
}

In Startup.cs the configuration is built using the config files and assigned to the Configuration property.

public Startup(IHostingEnvironment env)
{
    // Read the appsetting.json file for the configuration details
    var builder = new ConfigurationBuilder()
        .SetBasePath(env.ContentRootPath)
        .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
        .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true)
        .AddEnvironmentVariables();
    Configuration = builder.Build();
}

The Configure method is used to configure the services added to the dependency injection system. This is where log providers are configured. For the AWS.Logger.AspNetCore the configuration for the provider is loaded from the Configuration property and the AWS provider is added to the ILoggerFactory.

public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
{
    // Create a logging provider based on the configuration information passed through the appsettings.json
    loggerFactory.AddAWSProvider(this.Configuration.GetAWSLoggingConfigSection());

    ...