c# - Unique log file for each instance of class

Question

I am currently running a windows service that creates multiple instances of a class.

At the top of the service class and every other class in my solution, I have something like this:

private static readonly ILog _log = LogManager.GetLogger(typeof(SomeClassTypeHere));

In my App.config, I have Log4Net configured for a single file:

<log4net debug="true">
    <appender name="RollingFileAppender" type="log4net.Appender.RollingFileAppender">
      <file value="LogsSomeLogFileName.xml" />
      <appendToFile value="true" />
      <rollingStyle value="Size" />
      <countDirection value="1" />
      <maxSizeRollBackups value="30" />
      <maximumFileSize value="10MB" />
      <staticLogFileName value="true" />
      <lockingModel type="log4net.Appender.FileAppender+MinimalLock" />
      <layout type="log4net.Layout.XmlLayoutSchemaLog4j">
        <locationInfo value="true" />
      </layout>
    </appender>

    <root>
      <level value="INFO" />
      <appender-ref ref="RollingFileAppender" />
    </root>
  </log4net>

This works great in most respects, and everything logs to a single file. However, I'd really like to create a separate log file for each instance of a particular class that my service creates.
This is a class that we often need to monitor for support and we can have a handful of instances running at the same time.
We don't know which instances will be running at a given time, so it makes creating static files in the configuration kinda painful.

I tried taking off the readonly modifier and setting the following in the class constructor:

_log = LogManager.GetLogger("DataCollectionClass_" + deviceName + "_" + DateTime.Now.ToString("MMddyyyy"), typeof(SomeClassTypeHere));

But that requires that I define an appender manually in the configuration, which would be cumbersome and tough to keep up with.

Any thoughts on doing this in L4N? I have seen links here but don't really know if that much frameworking is necessary.

Answer 1

The code below shows how you can programatically configure log4Net without using a configuration file to achieve the effect you're looking for. Basically, it just involves creating a named logger and adding to the hierarchy.

I used as a starting point one of the answers from here.

using log4net;
using log4net.Appender;
using log4net.Layout;
using log4net.Repository.Hierarchy;

namespace LoggerTest
{
    class Program
    {
        static void Main(string[] args)
        {
            DeviceConnection dev1 = new DeviceConnection("Device1");
            DeviceConnection dev2 = new DeviceConnection("Device2");

            dev1.DoSomething();
            dev2.DoSomething();
        }
    }

    public class DeviceConnection
    {
        private string name;
        private readonly ILog logger;

        public DeviceConnection(string _name)
        {
            name = _name;

            logger = TestLogger.AddNamedLogger(name);

            logger.Info("----  Begin Logging for DeviceConnection: " + name);
        }

        public void DoSomething()
        {
            logger.Info("Doing something for device connection " + name);
        }
    }

    public static class TestLogger
    {
        private static PatternLayout _layout = new PatternLayout();
        private const string LOG_PATTERN = "%d [%t] %-5p %m%n";

        public static string DefaultPattern
        {
            get { return LOG_PATTERN; }
        }

        static TestLogger()
        {
            _layout.ConversionPattern = DefaultPattern;
            _layout.ActivateOptions();

            Hierarchy hierarchy = (Hierarchy)LogManager.GetRepository();
            hierarchy.Configured = true;
        }

        public static PatternLayout DefaultLayout
        {
            get { return _layout; }
        }

        public static ILog AddNamedLogger(string name)
        {
            Hierarchy hierarchy = (Hierarchy)LogManager.GetRepository();
            Logger newLogger = hierarchy.GetLogger(name) as Logger;

            PatternLayout patternLayout = new PatternLayout();
            patternLayout.ConversionPattern = LOG_PATTERN;
            patternLayout.ActivateOptions();

            RollingFileAppender roller = new RollingFileAppender();
            roller.Layout = patternLayout;
            roller.AppendToFile = true;
            roller.RollingStyle = RollingFileAppender.RollingMode.Size;
            roller.MaxSizeRollBackups = 4;
            roller.MaximumFileSize = "100KB";
            roller.StaticLogFileName = true;
            roller.File = name + ".log";
            roller.ActivateOptions();

            newLogger.AddAppender(roller);

            return LogManager.GetLogger(name);
        }
    }
}