Alois Kraus


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Most people using Workflow Foundations only know TrackingParticipants to enable activity tracing. With WF 4 the Sql TrackingParticipant was deprecated and replaced by EtwTrackingParticipant. WF has been wasteful with system resources since its very beginning but it has become better with WF 4. If you think that a SQL tracking participant is a good idea think again why MS did deprecate it:

[ObsoleteAttribute("The System.Workflow.* types are deprecated.  Instead, please use the new types from System.Activities.*")]
public sealed class SqlTrackingService : TrackingService, 

You should not try to create your own version of it because it is such a brilliant idea. It never was and never will be a well performing tracing destination. Lets see how far we get with the new ETW support for WF. The easiest way for e.g. a WF Console application is to add it directly to your WorkflowInvoker:

static void Main(string[] args)
    Activity workflow1 = new Workflow1();
    var invoker = new WorkflowInvoker(workflow1);
    invoker.Extensions.Add(new EtwTrackingParticipant());

Another option is to enable it indirectly via your App.config

    <source name="System.Activities"
            switchValue="Information, ActivityTracing"
        <add name="console" type="System.Diagnostics.DefaultTraceListener"/>

There is no mention of ETW in the used listeners but the ETW listener is added automatically when you have trace listeners for System.Activities configured.

Now you can enable ETW tracing with xperf like this:

xperf -on proc_thread+Loader -start workflow -on c651f5f6-1c0d-492e-8ae1-b4efd7c9d503  

The guid is the ETW provider for WCF and WF tracing. Its name is "Microsoft-Windows-Application Server-Applications". This xperf command will create in your root folder a kernel.etl and user.etl file to which the events are logged to. The default buffer size is 20 MB which you can alter if the event rate is higher than the buffer can be flushed to disc.

To stop tracing you can use

xperf -stop -stop workflow -d c:\temp\workflow.etl   

Finally you want to watch your traces WPA. Navigate to Generic Events and open the "Microsoft-Windows-Application Server-Applications" event provider:


There you see directly how your activities were scheduled and executed along with their activity arguments as long as they have a string representation. Since we have ETW we can add our own traces to ETW and the system wide profiling events as well to get the full picture in one file with a good analysis tool. Besides being central you have also chosen one of the fasted possible ways to write tracing information to an output device. The slowest thing is the DefaultTraceListener in your App.config which writes them via OutputDebugString. These events show up in VS in the output window which is nice but the output speed of OutputDebugString is not great. If you want to get maximum performance you need to write your own NullTraceListener which simply discards all traced data to enable writing only to ETW.

posted on Thursday, February 6, 2014 10:21 AM