Seq.Client.Log4Net

An Apache log4net appender that writes events to Seq.

Important

Like much of the log4net ecosystem, Seq's support for log4net is in maintenance mode.

Seq works best with richly-structured event data like that produced by Serilog, ASP.NET Core and NLog. These libraries are actively developed and have up-to-date support for modern application requirements.

Getting started

The Seq appender for log4net supports both .NET Framework 4.0+, and .NET Core via .NET Standard 2.0.

To install Seq.Client.Log4Net from NuGet, at the Visual Studio Package Manager console, type:

Install-Package Seq.Client.Log4Net

Then, add the appender to your log4net configuration:

<appender name="SeqAppender" type="Seq.Client.Log4Net.SeqAppender, Seq.Client.Log4Net" >
  <bufferSize value="1" />
  <serverUrl value="http://my-seq" />
  <apiKey value="" />
</appender>

Set the serverUrl value to the address of your Seq server. Set the apiKey value to your Seq API key, if required.

Finally, add a reference to the appender in the appropriate configuration section:

<root>
  <level value="INFO" />
  <appender-ref ref="SeqAppender" />
</root>

Writing events

That's it! When you write log events to your log4net ILogger:

log.InfoFormat("Hello, {0}, from log4net!", Environment.UserName);

They'll appear beautifully in Seq.

Performance

By default, the appender is synchronous. This can lead to application slowdowns.

For acceptable production performance, we recommend the use of Log4Net.Async and a buffer size of 100 or greater. See this log4net configuration for full configuation sample.

Note regarding NLog 4.0 and SLAB clients:

This repository originally included Seq.Client.NLog, targeting NLog 4.0, and Seq.Client.Slab, targeting Microsoft SLAB. The NLog client has been replaced with the much-improved NLog.Targets.Seq, while the SLAB client is now deprecated with no replacement currently planned. Both of these projects can be viewed in the deprecated-nlog-slab branch.