The Site Reliability Workbook

Chapter 16. Canarying Releases

By Alec Warner and Štěpán Davidovič with Alex Hidalgo, Betsy Beyer, Kyle Smith, and Matt Duftler

Release engineering is a term we use to describe all the processes and artifacts related to getting code from a repository into a running production system. Automating releases can help avoid many of the traditional pitfalls associated with release engineering: the toil of repetitive and manual tasks, the inconsistency of a nonautomated process, the inability of knowing the exact state of a rollout, and the difficulty of rolling back. The automation of release engineering has been well covered in other literature—for example, books on continuous integration and continuous delivery (CI/CD).¹

We define canarying as a partial and time-limited deployment of a change in a service and its evaluation. This evaluation helps us decide whether or not to proceed with the rollout. The part of the service that receives the change is “the canary,” and the remainder of the service is “the control.” The logic underpinning this approach is that usually the canary deployment is performed on a much smaller subset of production, or affects a much smaller subset of the user base than the control portion. Canarying is effectively an A/B testing process.

We’ll first cover the basics of release engineering and the benefits of automating releases to establish a shared vocabulary.

Release Engineering Principles

The basic principles of release engineering are as follows:

Reproducible ...