Improving the Deployment Experience of a Ten-Year Old Application - Code as Craft
In 2018, Etsy migrated its service infrastructure from self-managed data centers to cloud provisioning. (We blogged about it at the time.) The change opened up opportunities for improvements to technical processes across the company. For the Search team, the flexible scaling that comes with a cloud environment allowed us to completely reevaluate a somewhat cumbersome deployment process. Inspired by the existing architectural pattern of canary rollouts, we wrote a new custom tool to supplement our existing deployment infrastructure.
What we ended up with, after three months of effort, was a more scalable, more developer-friendly, and ultimately a more robust way to roll out changes to Search.
Historically, we deployed our stack on two separate sets of hosts, in what’s known as a blue-green strategy. At any one time, only one set of hosts is live; the other set, or “side,” is dark. Both sides were always fully scaled and ready to serve traffic, but only the live side was accessible to the public internet.
We refer to the two sets of hosts as “flip” and “flop”, named after the circuit that is a fundamental building block of modern computers. We point our monolithic PHP web application to whichever side should be active via some lines of code in a configuration file.
