EventSourceProxy

EventSourceProxy (ESP) is the easiest way to add scalable Event Tracing for Windows (ETW) logging to your .NET program.

Now in NuGet!

There are now two versions of ESP:

• EventSourceProxy - works with the .NET Framework - System.Diagnostics.Tracing
• EventSourceProxy.NuGet - works with the EventSource library in NuGet - Microsoft.Diagnostics.Tracing

Get EventSourceProxy (ESP) from NuGet

Follow @jonwagnerdotcom for latest updates on this library or code.jonwagner.com for more detailed writeups.

Why You Want This

• You really should be logging more than you do now.
• ETW is the best way to log in Windows.
• It's about zero effort to add logging to new code.
• It's zero effort to add logging to existing interfaces.
• Generated IL keeps overhead low, and it's almost nothing if tracing is off.

Here is ESP implementing a logging interface for you automatically:

public interface ILog
{
	void SomethingIsStarting(string message);
	void SomethingIsFinishing(string message);
}

// yeah, this is it
var log = EventSourceImplementer.GetEventSourceAs<ILog>();

log.SomethingIsStarting("hello");
log.SomethingIsFinishing("goodbye");

Here is ESP doing the hard work of implementing an EventSource if you really want to do that:

public abstract MyEventSource : EventSource
{
	public abstract void SomethingIsStarting(string message);
	public abstract void SomethingIsFinishing(string message);
}

// ESP does the rest
var log = EventSourceImplementer.GetEventSourceAs<MyEventSource>();

Here is ESP wrapping an existing interface for tracing:

public interface ICalculator
{
	void Clear();
	int Add(int x, int y);
	int Multiple(int x, int y);
}

public class Calculator : ICalculator
{
	// blah blah
}

Calculator calculator = new Calculator();

// again, that's it
ICalculator proxy = TracingProxy.CreateWithActivityScope<ICalculator>(calculator);

// all calls are automatically logged when the ETW source is enabled
int total = proxy.Add(1, 2);

And let's say that your interface doesn't look at all like what you want logged. You can add rules to clean all that up:

Say you have the following interface:

interface IEmailer
{
	void Send(Email email, DateTime when);
	void Receive(Email email);
	void Cancel(string from, string to, DateTime earliest, DateTime latest);
}

class Email
{
	public string From;
	public string To;
	public string Subject;
	public string Body;
	public IEnumerable<byte[]> Attachments; 
}

Set up rules on how ESP should trace the data to ETW:

TraceParameterProvider.Default
	.For<IEmailer>()
		.With<Email>()
			.Trace(e => e.From).As("Sender") 
			.Trace(e => e.To).As("Recipient")
			.Trace(e => e.Subject).As("s")
				.And(e => e.Body).As("b")
				.TogetherAs("message")
			.Trace(e => String.Join("/", e.Attachments.Select(Convert.ToBase64String).ToArray()))
				.As("attachments")
	.For<IEmailer>(m => m.Send(Any<Email>.Value, Any<DateTime>.Value)
		.Ignore("when");
	.ForAnything()
		.AddContext("user", () => SomeMethodThatChecksIdentity());

And now the Send method will log:

* Sender : From
* Recipient : To
* Message : { "s":subject, "b":body }
* Attachments : [ base64, base64 ]
* User : current user

So, this is great for adding logging to any interface in your application.

Features

• Automatically implement logging for any interface, class derived from EventSource.
• Takes all of the boilerplate code out of implementing an EventSource.
• Supports EventSource and Event attributes for controlling the generated events.
• Supports reusing Keyword, Opcode, and Task enums in multiple log sources.
• Automatically proxy any interface and create a logging source.
• Add rules to transform parameters and objects from your interface to your log.
• Proxies also implement _Completed and _Faulted events.
• Automatically convert complex types to JSON strings for logging.
• Optionally override the object serializer.
• Optionally provide a logging context across an entire logging interface.
• Easily manage Activity IDs with EventActivityScope.

New in v2.0 - Logging Transforms

• Use attributes and configuration rules to transform your interface calls to entirely different logging calls. See Controlling Logged Data and Adding Additional Logging Context.

Documentation

Full documentation is available on the wiki!

Good References

• Want to get the data out of ETW? Use the Microsoft Enterprise Library Semantic Logging Application Block. It has ETW listeners to log to the console, rolling flat file, and databases, so you can integrate ETW with your existing log destinations.