Redesigning a public web service API is a major undertaking: 3 years, thousands of hours of work, new clients, new documentation, a series of releases... This is the story of the DNSimple API v2, a project that started with a single, innocuous GitHub pull request with the title "Proposal for versioned API" in December 2013, and which came to a successful general availability launch at the end of 2016. Simone will explain some of the decisions that the team took over the last 3 years that shaped the development of the API as well as challenges the team faced, and provide you with tips and techniques that may help you in your next major API project. Finally, the important question: what’s next?

1. The Great API Redesign
Simone Carle,, DNSimple

5. "This PR is a first step towards API versioning and
using a dedicated hostname for API."

6. "This PR is a first step towards API versioning and
using a dedicated hostname for API."
Dec 28, 2013

7. Dec 28, 2013
v0
API v0

8. API v0
• Same hostname as website
• No versioning
• No metrics
• Shared Rails controllers

9. It worked ™ 😬

10. GET https://dnsimple.com/domains.json
GET https://dnsimple.com/domains.json

11. Jan 14, 2014Dec 28, 2013
v0 v1
API v1

12. API v1
• Introduce hostname api.dnsimple.com
• Introduce path-based versioning
• SGll uses the same Rails controllers
• Simple transiGon through minimal changes

13. GET https://api.dnsimple.com/v1/domains

14. Why a separate hostname?
• Easily flag requests as API requests
• Improved error handling due to clear indicaGon of what
is an API call
• Adds the ability to extract API code from controllers
• Provides easier scaling

15. Why path-based versioning?
The approach I followed is simple.
May be not the most restful, but it's the one very
commonly adopted that will also allow us to
switch to a mime-based approach (in case we
want to follow that route in the future).

16. Why path-based versioning?
• API version is embedded in the path and it prefixes the URL
• Everything in the URL is easily visible in logs
• Easiest implementaGon for both producGon and
consumpGon
• Hi,ng path-based versioned APIs with a browser is easy
• New versions increase the major number
• Path and verb changes can be introduced at major version

17. Jan 14, 2014Dec 28, 2013
v0 v1
API v1

18. Jan 14, 2014Dec 28, 2013
v0 v1 v2
API v2

19. Separate ApplicaDon
• Use of a separate
(sub)applicaGon
• No longer Gghtly coupled to
the Rails controllers
hWp://hanamirb.org
hWp://confreaks.tv/videos/railsconf2016-developing-and-maintaining-a-plaorm-with-rails-and-lotus

20. the Roadmap
• MulG-account
• Reusable shared business logic
• Response serializaGon
• PaginaGon, SorGng and Filtering
• AuthenGcaGon
• Rate limiGng
• Webhooks
• API clients

23. May 2, 2016
API clients
Java PHP
May 2, 2016 Sep 6, 2016 Sep 13, 2016
hWps://slidr.io/weppos/using-go-to-guide-api-design-decisions-dotgo-2016

24. API clients
• Developing clients gets easier with each new client
• Common design paWerns emerge
• Shared HTTP fixtures
• We built a foundaGon for API clients development
hWps://blog.dnsimple.com/2017/01/api-client-tesGng-with-hWp-fixtures/

25. PrioriDes
• Gathered metrics on v1 endpoint usage
• PrioriGzed implementaGon based on usage

26. Jan 14, 2014 Mar 9, 2016 (Beta)
Dec 13, 2016 (GA)
Dec 28, 2013
v0 v1 v2
API v2

27. Stats
• 717 Days from "Start" to "Finish"
• 3 (almost) full-Gme team members out of 11 total, with a
collaboraGve effort from the enGre DNSimple team
• 4 official API clients, with 2 more under development
• 75 API methods currently available (*)
• 251 Dckets across 7 major milestones
• ~423 API related support Dckets handled in the last year
• ~1934 commits across the 4 API clients and applicaGon

28. What's next?
• Facilitate transiGon to API v2
• Implement new methods (e.g. cerGficate, pricing)
• Adopt a formal language to describe the API

29. Open API
hWps://www.openapis.org/

30. Lessons
• Simple transiGon through minimal changes
• Be a producer and a consumer
• Provide official clients (and/or contribute)
• Measure decisions
• Invest into the API

31. Thanks!
DNSimple
dnsimple.com
@dnsimple
Simone CarleS
simonecarle,.com
@weppos
hWps://slidr.io/weppos