title: Application Strangler Pattern Experiences & Thoughts
body: <p>Just recently I came over an idea called the <strong>Application Strangler Pattern</strong>. As I understand it it is a solution to the problem with large legacy systems. The idea is to create a new application <em>around</em> the old application. The cost and risk of this will be much less than a complete rewrite of the system. Slowly, over time, the new application will do more and more of the work and eventually strangle the old legacy application. In the mean time developers get to work in a clean, new system with higher efficiency and hopefully producing much better code.</p>
  
  <p>Where I work now we have come to the point were new functionality, even seemingly trivial things, takes a long time to develop, with a high risk of breaking something. We sit on about a million lines of code, with unit test coverage of perhaps 1-2%. The system is a SOA system using web services (neither is really necessary) and is more procedural in style than object oriented. The system is both web &amp; win, all written in .net programming languages.</p>
  
  <p><strong>Finally the question:</strong>
  In considering this new idea/pattern, I want to know if anyone has had any experience with using this pattern they would like to share. For example, what would be a good way of implementing it (hooking up to events from the old application, for example)? Also, if anyone has any thoughts on the subject, why it would be a good or bad idea, that would be appreciated as well.</p>
  
  <p><strong>References:</strong></p>
  
  <ul>
  <li><a href="http://martinfowler.com/bliki/StranglerApplication.html" rel="noreferrer">Martin Fowler blog post</a></li>
  <li><a href="http://www.hanselman.com/blog/HanselminutesPodcast165WorkingEffectivelyWithLegacyCodeWithMichaelFeathers.aspx" rel="noreferrer">Hanselminutes with Michael Feathers</a></li>
  </ul>