Log4net, eliminate duplicate messages

Question

is there any option to setup log4net to eliminate duplicate messages? I have an application which works in cycles...there is an infinate while cycle. If any error occure (for example database is not accesible), same message is logged again and again in every loop. I need to log the message just once.

Answer 1

I have implemented log4net filter to eliminate same messages during specified time interval.

The class:

public class DuplicityFilter : FilterSkeleton
{
    private String lastMessage = null;
    private List<Tuple<DateTime, String>> lastMessages = new List<Tuple<DateTime,string>>();

    private Int32 _timeWindow = 0;
    public Int32 timeWindow
    {
        get { return _timeWindow; }
        set { _timeWindow = value; }
    }

    public Boolean _lastOnly = false;
    public Boolean lastOnly
    {
        get { return _lastOnly; }
        set { _lastOnly = value; }
    }

    public override FilterDecision Decide(log4net.Core.LoggingEvent loggingEvent)
    {
        if (_lastOnly)
        {
            if (lastMessage == loggingEvent.RenderedMessage)
            {
                return FilterDecision.Deny;
            }
            else
            {
                lastMessage = loggingEvent.RenderedMessage;
                return FilterDecision.Accept;
            }
        }
        else
        {
            if (_timeWindow <= 0)
                return FilterDecision.Accept;

            // Removes old messages
            lastMessages.RemoveAll(m => m.Item1 < DateTime.Now.AddSeconds(0 - _timeWindow));

            if (!lastMessages.Any(m => m.Item2 == loggingEvent.RenderedMessage))
            {
                lastMessages.Add(new Tuple<DateTime, string>(loggingEvent.TimeStamp, loggingEvent.RenderedMessage));
                return FilterDecision.Accept;
            }
            else
            {
                return FilterDecision.Deny;
            }
        }
    }

And the XML definition:

  <filter type="your.namespace.here.DuplicityFilter">
    <timeWindow value="900" /> <!-- 15min -->
    <lastOnly value="false" />
  </filter>