Runtime Flow blog (Understanding a control flow in a running .NET application)

Runtime Flow v1.5.1 released: Fixed incorrect monitoring started for an auxiliary process when it was launched by the main target executable.

Download links: Visual Studio edition, Portable edition.

Runtime Flow v1.5.0 released: added support for Visual Studio 2015 and fixed the “Output file name required for the Start Project option” error when starting monitoring in a localized Visual Studio edition.

Download the Visual Studio edition.

Runtime Flow v1.3.5 released: added support for Visual Studio 2013 and added the ability to run without .NET 3 installed in Visual Studio 2010+.

Download link: Visual Studio edition.

Runtime Flow v1.3.4 released: fixed a problem with Visual Studio 2012 registration on 64bit Windows.

Download link: Visual Studio edition.

Runtime Flow v1.3.3 released: added support for Visual Studio 2012 RC.

Download link: Visual Studio edition.

Runtime Flow can monitor a .NET application running in IIS, but currently it requires manual configuration and only one IIS worker process (w3wp.exe) can be monitored. Below are the steps I used to monitor a sample ASP.NET MVC2 application configured to use local IIS Web server, created in Visual Studio 2010 and running on Windows 7:

1. Enable profiling for w3wp.exe.

a) Find the application pool for the app.

Check IIS Manager, Sites – Default Web Site – MvcApplication1, Basic Settings. In my case the pool is DefaultAppPool:

b) Enable user profile loading for the pool.

IIS Manager, Application Pools, DefaultAppPool, Advanced Settings, Process Model – Load User Profile, set to True:

c) Find SID of the pool account.

From the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProfileList key find ProfileImagePath with DefaultAppPool. In my case the SID is S-1-5-82-3006700770-424185619-1745488364-794895919-4004696415:

d) Set environment variables to invoke Runtime Flow profiler.

Using the found SID, add two string values to HKEY_USERS\S-1-5-82-3006700770-424185619-1745488364-794895919-4004696415\Environment:

Cor_Enable_Profiling=1
COR_PROFILER={C967CF3F-79BF-49a5-A10F-D5B269DB9E54}

Note that if you use IntelliTrace it can overwrite these registry values.

2. Close all running w3wp.exe processes.

In IIS Manager restart server.

3. Run monitoring.

In Runtime Flow – Customized Run, uncheck Stop monitoring when the command completes. Set Command to “C:\Program Files\Internet Explorer\iexplore.exe”. Set Command arguments to “http://localhost/MvcApplication1”. Optionally set Options – Monitoring Filter to “Module == MvcApplication1.dll”:

After you click Run, you will see how your application runs:

Update (July 28, 2018): For Windows 7 SP1 you may need to additionally edit the applicationHost.config file. See How to configure environment variables in an IIS 7 application? for details.

Runtime Flow v1.3.2 released: fixed compound exceptions handling.

Download links: Visual Studio edition, Portable edition.

Runtime Flow v1.3.1 released – added a .NET 4.0 portable edition executable with deeper call stack support, enabled Options during monitoring.

Download links: Visual Studio edition, Portable edition.

When viewing deep function calls in the Runtime Flow window you may hit a WPF layout recursion limit. To illustrate this problem I created a very simple application:

    class Program
    {
        static void Main(string[] args)
        {
            f(1);
        }

        static void f(int i)
        {
            if (i < 500)
                f(i + 1);
        }
    }

In Runtime Flow portable you can open maximum 58 recursive calls:

If you try to see more calls you get the following error:

The same problem exists when you view monitoring results in Visual Studio 2008/2005. In .NET 4.0 the layout recursion limit is increased from 255 to 4096. So in Visual Studio 2010 you can view much deeper stacks (though not 1024 deep due to other limitations).

I’ve created an additional Runtime Flow portable binary built for .NET 4.0 to enable more deep stack investigations:

If you have .NET 4.0 installed on the machine, it is now recommended to use RuntimeFlowPortable.NET40.exe instead of RuntimeFlowPortable.NET35.exe. It supports stacks up to 285 function calls:

Download link: Runtime Flow portable edition v1.3.1.

I’ve added the ability to pause and resume monitoring. After you’ve started monitoring (with Run or Customized Run) and have executed a use case, you can press the Pause button on the Runtime Flow toolbar:

Pause stops all updates to the Runtime Flow and Runtime Summary windows and eliminates most of monitoring overhead (speeding up the monitored application and limiting memory consumption). In this mode you can browse collected events and execute tasks in your application not required monitoring.

When you are ready to run a next use case, press the Resume button:

Resume clears the Runtime Flow and Runtime Summary windows and resumes normal monitoring events processing.

The most common case to not collect monitoring data is to skip application startup. For convenience, I’ve added the Monitor application startup option:

With Monitor application startup unchecked, no flow data is collected until you click the Resume button. This is useful when monitoring complex apps with very big initialization routines that you are not interested in.

Download links for Runtime Flow v1.3.0: Visual Studio edition, Portable edition.