TPL Data Flow Debugger Visualizer

TPL Data Flow

I first encounter TPL data flow (part of .NET 4.5 - TPL DTF) during the build conference (I attended  last year) but I must say I didn’t get it then. It sounded too much like RX which I was familiar with. Recently during one of my projects that required high performance CPU bounded – high throughput and low latency my colleague Alon the gave the idea – why not using TPL data flow and from then my world changed forever. It’s amazing to how many systems this technology can be suitable to,and for the project I was working on it was perfect. For those of you that are not yet familiar with this technology I suggest reading the article from here and see this amazing example of kinect and TPL DTF here – you’ll thank me later.

So I created some crazy TPL data flow networks on runtime (~100k different networks) and it worked getting 100% CPU most of the time, leveraging all the cores and getting really good performance – but it was really hard to debug and to understand the flow from the code. It was Alon again that suggested to write debug visualizer – so I did. This is my insights from the process.

Writing Debugger Visualizer

I don’t know how many of you had the chance to implement debugger visualizer but it is really straightforward if you need only view on a simple object just follow 5-6 steps:read here. Finally put your assembly in the visualizer folder (e.g. for VS 11 C:\Program Files (x86)\Microsoft Visual Studio 11.0\Common7\Packages\Debugger\Visualizers) and you’re done. This is very simple if your debugging target is simple and serializable. I from the other hand had few issues.

The Issues I encountered during the implementation

Debugger Visualizer Target cannot be interface

   This really surprised me because I know the target I wanted was IDataFlow which is the common interface of TPL data flow which all the blocks need to implement and I discovered that it’s impossible,the target must be a type (can be common base class but not an interface). My solution to this issue was not perfect – I added multiple attributes with all the build in blocks as target.  It’s not that bad because the build in blocks are a good start and as long as you start from build in block (what you normally do) then it will discover the rest of the linked block even if they are not part of the build in blocks. In addition it’s not recommended to implement IDataFlow block on your own – there is a lot to take care of: locking synchronization,buffering and more. If one of you Microsoft guys are listening I think adding support of Interface as target of debug visualizer can be very handy.

Read more: Offir Shvartz

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