UdpTraceListener - a UDP TraceListener compatible with log4net/log4j

March 13, 2013

This class is a TraceListener implementation that uses the log4j XML format and sends the XML to a UDP socket. This means you can configure a trace listener to send all your logs to something like http://log2console.codeplex.com.. There is also Harvester which has a TraceListener implementation for streaming over a network.

Just configure a new UDP receiver in log4console and they messages will start to stream through. This works nicely with LightSpeed, where you can configure it to send its SQL statements to a TraceListener.

Feel free to include the source wherever you need it, it’s under an MIT licence.

	class Program
	{
	static void Main(string[] args)
	{
	Trace.Listeners.Add(new UdpTraceListener());

	Thread thread1 = new Thread(() => {
	Trace.WriteLine("I'm in a new thread 1");
	Trace.WriteLine("I'm in a new thread 2");
	Trace.WriteLine("I'm in a new thread 3");
	});

	Thread thread2 = new Thread(() =>
	{
	Trace.WriteLine("I'm in a new thread also 1");
	Trace.WriteLine("I'm in a new thread also 2");
	Trace.WriteLine("I'm in a new thread also 3");
	});

	thread1.Start();
	Trace.WriteLine("Hello world");
	Trace.WriteLine("Warning Will Robinson", "warning");
	thread2.Start();
	Trace.WriteLine("Catastrophic failure", "error");
	Trace.WriteLine(42, "fatal");
	}
	}

view raw gistfile1.cs hosted with ❤ by GitHub

	public class UdpTraceListener : TraceListener
	{
	// For 3.5/2 you can use a List but the class is no longer thread safe.
	//private Stack<string> _messageBuffer;

	private UdpClient _udpClient;
	private ConcurrentStack<string> _messageBuffer;
	private string _loggerName;

	private static readonly string _xmlPrefix = "log4j";
	private static readonly string _xmlNamespace = "http://jakarta.apache.org/log4j/";

	public override bool IsThreadSafe
	{
	get
	{
	return true;
	}
	}

	public UdpTraceListener()
	: this("localhost", 7071, "UdpTraceListener")
	{

	}

	public UdpTraceListener(string host, int port, string loggerName)
	{
	_loggerName = loggerName;
	_messageBuffer = new ConcurrentStack<string>();
	_udpClient = new UdpClient();
	_udpClient.Connect(host, port);
	}

	public override void Write(string message)
	{
	Write(message, "info");
	}

	public override void WriteLine(string message)
	{
	Write(message, "info");
	Flush();
	}

	public override void WriteLine(string message, string category)
	{
	_messageBuffer.Push(GetEventXml(message, category));
	Flush();
	}

	public override void Write(string message, string category)
	{
	_messageBuffer.Push(GetEventXml(message, category));
	}

	private string GetEventXml(string message, string category)
	{
	// The format:
	//<log4j:event logger="{LOGGER}" level="{LEVEL}" thread="{THREAD}" timestamp="{TIMESTAMP}">
	// <log4j:message><![CDATA[{ERROR}]]></log4j:message>
	// <log4j:NDC><![CDATA[{MESSAGE}]]></log4j:NDC>
	// <log4j:throwable><![CDATA[{EXCEPTION}]]></log4j:throwable>
	// <log4j:locationInfo class="org.apache.log4j.chainsaw.Generator" method="run" file="Generator.java" line="94"/>
	// <log4j:properties>
	// <log4j:data name="log4jmachinename" value="{SOURCE}"/>
	// <log4j:data name="log4japp" value="{APP}"/>
	// </log4j:properties>
	//</log4j:event>

	string level = "INFO";
	if (string.IsNullOrEmpty(category))
	category = "info";

	switch (category.ToLower())
	{
	case "fatal":
	level = "FATAL";
	break;

	case "warning":
	case "warn":
	level = "WARN";
	break;

	case "error":
	level = "ERROR";
	break;

	case "debug":
	level = "DEBUG";
	break;

	case "trace":
	level = "TRACE";
	break;

	default:
	break;
	}

	StringBuilder builder = new StringBuilder();

	XmlWriterSettings settings = new XmlWriterSettings();
	settings.OmitXmlDeclaration = true;

	XmlWriter writer = XmlWriter.Create(builder, settings);
	WriteLog4jElement(writer, "event");
	writer.WriteAttributeString("logger", _loggerName);
	writer.WriteAttributeString("level", level);
	writer.WriteAttributeString("thread", Thread.CurrentThread.ManagedThreadId.ToString());
	writer.WriteAttributeString("timestamp", XmlConvert.ToString(ConvertToUnixTimestamp(DateTime.Now)));

	WriteLog4jElement(writer, "message");
	writer.WriteCData(RemoveInvalidXmlChars(message));
	writer.WriteEndElement();
	WriteLog4jElementString(writer, "NDC", "");
	WriteLog4jElementString(writer, "throwable", "");

	WriteLog4jElement(writer, "locationInfo");
	writer.WriteAttributeString("class", "");
	writer.WriteAttributeString("run", "");
	writer.WriteAttributeString("file", "");
	writer.WriteAttributeString("line", "1");
	writer.WriteEndElement();

	WriteLog4jElement(writer, "properties");
	WriteLog4jElement(writer, "data");
	writer.WriteAttributeString("name", "log4jmachinename");
	writer.WriteAttributeString("value", Environment.MachineName);
	writer.WriteEndElement();

	WriteLog4jElement(writer, "data");
	writer.WriteAttributeString("name", "log4japp");
	writer.WriteAttributeString("value", Assembly.GetCallingAssembly().FullName);
	writer.WriteEndElement();
	writer.WriteEndElement();

	writer.WriteEndElement();

	writer.Flush();
	return builder.ToString();
	}

	private string RemoveInvalidXmlChars(string text)
	{
	var validXmlChars = text.Where(x => XmlConvert.IsXmlChar(x)).ToArray();
	return new string(validXmlChars);
	}

	private void WriteLog4jElement(XmlWriter writer, string name)
	{
	writer.WriteStartElement(_xmlPrefix, name, _xmlNamespace);
	}

	private void WriteLog4jElementString(XmlWriter writer, string name, string value)
	{
	writer.WriteElementString(_xmlPrefix, name, _xmlNamespace, value);
	}

	private double ConvertToUnixTimestamp(DateTime date)
	{
	DateTime epoch = new DateTime(1970, 1, 1, 0, 0, 0, 0);
	TimeSpan sinceEpoch = date.ToUniversalTime() - epoch;
	return Math.Floor(sinceEpoch.TotalMilliseconds);
	}

	public override void Flush()
	{
	foreach (string xmlMessage in _messageBuffer)
	{
	byte[] payload = Encoding.UTF8.GetBytes(xmlMessage);
	_udpClient.Send(payload, payload.Length);
	}

	_messageBuffer.Clear();
	base.Flush();
	}

	protected override void Dispose(bool disposing)
	{
	Flush();
	_udpClient.Close();

	base.Dispose(disposing);
	}

	public override void TraceEvent(TraceEventCache eventCache, string source, TraceEventType eventType, int id, string format, params object[] args)
	{
	switch (eventType)
	{
	case TraceEventType.Critical:
	case TraceEventType.Error:
	WriteLine(string.Format(format, args), "error");
	break;

	case TraceEventType.Verbose:
	WriteLine(string.Format(format, args), "debug");
	break;

	case TraceEventType.Warning:
	WriteLine(string.Format(format, args), "warn");
	break;

	case TraceEventType.Information:
	case TraceEventType.Resume:
	case TraceEventType.Start:
	case TraceEventType.Stop:
	case TraceEventType.Suspend:
	case TraceEventType.Transfer:
	default:
	WriteLine(string.Format(format, args), "error");
	break;
	}
	}
	}

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I'm Chris Small, a software engineer working in London. This is my tech blog. Find out more about me via Github, Stackoverflow, Resume