Using EntLib6 ETW Listeners

Using EntLib6 ETW Listeners

*NOTE: this is based on a preview release and may not be the same as the final release *

One of the reasons that developers haven't adopted ETW yet is that they already have logging solutions. Usually they are home-grown flat-file or database logs, or are based on a library such as nLog or Log4Net. If you have one of these solutions, you can start using ETW now as your EventSources, but log the data to your existing back-end store.

The Microsoft Patterns and Practices Team is releasing a set of ETW listeners to handle all your logging target needs. The Semantic Logging Application Block is available on NuGet. It can handle logging to:

• ConsoleEventListener - logging to the console for development
• FlatFileEventListener - logging to a set of flat files as XML, JSON or Text
• RollingFlatFileEventListener - logging to a set of flat files that automatically rotates to a new file
• DatabaseEventListener - logging to a .NET database
• SqlDatabaseEventListener - logging to a SQL Server database
• AzureTableEventListener - logging to SQL Azure in the cloud

Let's take a look at a few of the listeners. The simplest is the ConsoleEventListener:

// create a logger
var log = EventSourceImplementer.GetEventSourceAs<ICalculatorEventSource>();

// create a console listener
ConsoleEventListener listener = new ConsoleEventListener();

// enable listening
listener.EnableEvents((EventSource)log, EventLevel.LogAlways, (EventKeywords)(-1));

log.Clear();
log.Add(1, 2);

This generates the following output:

SourceId : 5534a855-95dc-5099-33e3-5b8e79fed6fa
EventId : 1
Keywords : 1
Level : Informational
Message : Clear
Opcode : Info
Task : 65533
Version : 0
Payload :
EventName : ClearInfo
Timestamp : 2013-03-04T18:31:38.7621609Z

SourceId : 5534a855-95dc-5099-33e3-5b8e79fed6fa
EventId : 2
Keywords : 2
Level : Informational
Message : Add 1 2
Opcode : Info
Task : 65532
Version : 0
Payload : [x : 1] [y : 2]
EventName : AddInfo
Timestamp : 2013-03-04T18:31:38.7701619Z

As you can see, the listener found the events from our source and logged them to the console.

You can log them to a file just as easily:

// create a file listener
var listener = new FlatFileEventListener(@"c:\temp\calc.log");

The file listeners even let you control the format of the output, with built-in support for JSON or XML serialization:

var listener = new FlatFileEventListener(@"c:\temp\calc.log", new JsonEventTextFormatter());

The output is now:

{
	"SourceId":"5534a855-95dc-5099-33e3-5b8e79fed6fa",
	"EventId":2,
	"Keywords":"2",
	"Level":"Informational",
	"Message":"Add 1 2",
	"Opcode":"Info",
	"Task":65532,
	"Version":0,
	"Payload":{"x":1,"y":2},
	"EventName":"AddInfo",
	"Timestamp":"2013-03-04T18:36:03.1511259Z"
},

Try it out. It supports almost any kind of output you might need.