5 Anti-Patterns in Api Design - NDC London 2016
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The document discusses five common API anti-patterns affecting service design, specifically in relation to the fashion retailer ASOS. These include issues such as 'transparent server' where internal implementations are exposed, 'chauvinist server' that prioritizes server perspective, and 'demanding client' where client needs dictate API signatures. It emphasizes the importance of understanding boundaries and responsibilities in client-server interactions within microservice architectures.
![Anti-Pattern Chauvinist Server
H A T E O A S
Client most likely a server [wasteful to navigate]2
3 Client uses more than one server
6 Microservices: servers smaller, containing a couple of resources
4 UndeďŹned caching directives for hypermedia
Server hasnât got a clue what the application is1
5 Donât try to spare the client composing URLs](https://image.slidesharecdn.com/5anti-patternsinapidesign-ndclondon-160115153019/85/5-Anti-Patterns-in-Api-Design-NDC-London-2016-33-320.jpg)
5 Anti-Patterns in Api Design - NDC London 2016
- 2. W iiiiiiire Wiie 5 Anti-PatternsWho Are WeASOS ASOS is a global fashion destination for 20-somethings. From fashion advice, stories and inspiration, to more than 80,000 products available to buy on any device, ASOS, with its unbeatable service, is a true home for fashion lovers.
- 3. 5 Anti-PatternsIn NumbersASOS ~1 bln Turnover (ÂŁ) 1.1 bln visits / year 9.9 mln Active customers 58% International 3.7 M 3.3 M 2.4 M 885 K
- 4. API The Art of Presentation
- 5. API, API . . . . . . everywhere
- 6. API Iceberg âThis huge mass underneath the water that you can't see, the private API, is the biggest part of the whole opportunity.â Daniel Jacobson, Netflix - 2011
- 7. @aliostad Micro services â ⌠the microservice architectural style is an approach to developing a single application as a suite of small services, each running in its own process and communicating with lightweight mechanisms, often an HTTP resource APIâ Martin Fowler - Bliki
- 10. REST Caching
- 11. @aliostad Resources and representations REST Uniform Interface S e l f - d e s c r i p t i v e messages Hypermedia
- 13. @aliostad HTTP Client-Server GET /api/catalogue/products/123456 GET /api/catalogue/Products/123456 S e r v e r C o n c e r n
- 14. @aliostad HTTP Client-Server GET /api/catalogue/Products/123456 301 Moved Permanently Location /api/catalogue/products/123456 C l i e n t C o n c e r n GET /api/catalogue/Products/123456 ??? 1 2
- 15. @aliostad HTTP Client-Server M i x e d C o n c e r n GET /api/catalogue/Products/123456 200 OK max-age: 300 GET /api/catalogue/Products/123456 If-Modified-Since: Fri, 15 Jan 2016 10:28:16 GMT 304 Not Modified
- 17. @aliostad CSDS Client-Server Domain Separation â Client and server must deďŹne and live within their own bounded context â
- 18. CSDS Client-Server Domain Separation S e r v e r
- 19. API Restaurant
- 21. @aliostad CSDS Client-Server Domain Separation C l i e n t Can be a server itself1 2 Uses services of server(s) to bring value to end-user (directly or indirectly) 3 Free to take dependency on Serverâs public domain (Resource Comprehension) Normally keeps state but does not master it4
- 25. âserver exposes its internal implementation to its clientsâ Anti-Pattern Transparent Server server's private domain or the domain of its underlying dependencies bleeds into its public API
- 26. @aliostad E x a m p l e 1 Anti-Pattern Transparent Server
- 27. E x a m p l e 2 Always for a customer1 2 Only for customers currently shopping 3 Get expired after inactivity A couple of tables or a document database 4 Max one basket per customer Anti-Pattern Transparent Server
- 28. @aliostad E x a m p l e 2 POST /baskets?cid=908 201 Created Location: /baskets/123435455456 POST /baskets/123435455456{...} 200 OK x Anti-Pattern Transparent Server
- 29. @aliostad E x a m p l e 2 POST customer/me/basket {âŚ} 200 OK â Anti-Pattern Transparent Server
- 31. âdesigning the API from server's perspectiveâ Anti-Pattern Chauvinist Server Server pushes its thinking and process to the client resulting in the client becoming a subordinate
- 32. @aliostad Anti-Pattern Chauvinist Server H A T E O A S(and not hypermedia itself) Hypermedia as the Engine of Application (state)
- 33. Anti-Pattern Chauvinist Server H A T E O A S Client most likely a server [wasteful to navigate]2 3 Client uses more than one server 6 Microservices: servers smaller, containing a couple of resources 4 UndeďŹned caching directives for hypermedia Server hasnât got a clue what the application is1 5 Donât try to spare the client composing URLs
- 34. Anti-Pattern Chauvinist Server H A T E O A S? R e a l l y ? ?
- 36. âclient enforces its special needs onto the API signatureâ Anti-Pattern Demanding Client certain clients limitations (or reluctance to implement) become server's default behaviour
- 37. @aliostad Anti-Pattern Demanding Client GET /api/catalogue/products.xml GET /api/catalogue/products.json GET /api/catalogue/products?format=xml GET /api/catalogue/products?format=json x E x a m p l e 1 Bioenergy KDF REST API
- 38. @aliostad Anti-Pattern Demanding Client GET /api/catalogue/products Accept: application/json E x a m p l e 1 â
- 39. @aliostad Anti-Pattern Demanding Client E x a m p l e 2 GET /api/catalogue/products?client=mobile GET /api/catalogue/products?model=summary x
- 40. @aliostad Anti-Pattern Demanding Client E x a m p l e 2 âGET /api/catalogue/products?fields=foo,bar,jazz GET /api/catalogue/products_summary
- 42. âserver assumes the role of deďŹning client experienceâ Anti-Pattern Assuming Server server makes decisions on issues that are inherently client concerns
- 43. @aliostad E x a m p l e 1 Anti-Pattern Assuming Server GET /api/catalogue/products/pages/1 GET /api/catalogue/products/pages/2 x
- 44. E x a m p l e 1 Anti-Pattern Assuming Server GET /api/catalogue/products?from=1&count=30 â GET /api/catalogue/products?offset=1&limit=30
- 45. E x a m p l e 2 Anti-Pattern Assuming Server B r o w s e r s n i f f i n g
- 47. âclient takes on responsibilities that cannot fulďŹlâ Anti-Pattern Presumptuous Client Client presumes it can fulďŹl some responsibilities that are inherently serverâs
- 48. E x a m p l e s Anti-Pattern Presumptuous Client A P I Identity
- 49. E x a m p l e s Anti-Pattern Presumptuous Client I D S E R V E R Long Expiry Token ID Request A P I Token
- 50. E x a m p l e s Anti-Pattern Presumptuous Client I D S E R V E R ID Token ID Request A P I Access TokenAccess Token . . . ID Token â
- 51. @aliostad E x a m p l e s Client act as an authority for authentication or authorisation1 2 Client implements an algorithm that needs to be centralised on server 3 Client takes control of cache invalidation Anti-Pattern Presumptuous Client
- 52. @aliostad Microservices take importance of APIs to a new level1 2 Think of your API as a restaurant and remember the contrast with kitchen 3 Transparent Server: Exposing internals Re Cap 4 Chauvinist Server: Client becoming a subordinate 5 Demanding Client: Client enforcing special needs to API signature 6 Assuming Server: Server deciding client experience 7 Presumptuous Client: Client taking responsibilities cannot fulďŹl