<p>Last week, I <a href="began">http://spring.io/blog/2014/03/27/project-sagan-open-sourcing-spring-io">began this series</a> by announcing that the <a href="Sagan">http://github.com/spring-io/sagan">Sagan reference app is now open source and <a href="showed">https://vimeo.com/90126708">showed how to get up and running with it on your own machine.</p> <p>In this post, I want to walk through how we push Sagan into production at spring.io multiple times a day with zero downtime using <em>blue-green deployments</em>. You may have heard of this technique before; <a href="Martin">http://martinfowler.com/bliki/BlueGreenDeployment.html">Martin Fowler gave it a write-up</a> a few years ago, and there is a section on it in the highly-recommended book <a href="Continuous">http://www.amazon.com/gp/product/0321601912">Continuous Delivery</a>. In a nutshell, it goes like this:</p>