GOTO: https://github.com/dwyl/learn-api-design (latest version)

Essential learning for people building an API

Joking aside, starting a project "from scratch" is a opportunity (and privilege) few people get.
If you are fortunate enough to be in that position, do not take the task lightly.

Building the interface for a new project is nothing short of a Golden Ticket! So do your homework before you start!

Intro

Having a great API will make or break your project/product.

A few quotes from Joshua Bloch's Google Talk on "How To Design A Good API and Why it Matters"
and Kevin Lacker's (@Parse) "How to Design Great APIs"

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"You have one chance to get it right." 3:17

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"A bad API can be amoung a company's greatest liabilities... can cause an un-ending stream of support phonecalls ... and it can inhibit a company's ability to move forward" 2:51

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"Once you have a bad API, you can't change it, you are pretty much stuck with it forever." 3:12

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" ... A good API needs to appeal to the most powerful emotion: Laziness". 3:23

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"You need to be opinionated even when there is no right and wrong" 31:02

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"Always make your REST API as small/short as possible" 31:19

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Characteristics of a Good API

• Easy to learn (notice the priority placement of learn-ability...)
• Intuitive / Easy to use even without documentation
• Hard to misuse (write tests for "undesireable" behaviour)
• Easy to read and maintain code that uses it
• Sufficiently powerful to satisfy requirements
• Easy to evolve (the simpler the initial API the easier it will be to extend)
• Appropriate to audience (make it beginner friendly...)
• Opinionated (means people don't have to think)

Types of API

REST

Representational State Transfer (REST) is a software architecture style consisting of guidelines and best practices for creating scalable web services.

What is a RESTful web service?

ReST is a structured way of building web services and applications. When something is described as "RESTful" it simply means it follows a predefined predictable pattern for how it responds to requests.

Video Explanation of REST

• Intro to REST: http://youtu.be/llpr5924N7E
• Google Developers Intro to REST: https://www.youtube.com/watch?v=YCcAE2SCQ6k

Read more about REST APIs / RESTful Web Services

• REST Wikipedia: http://en.wikipedia.org/wiki/REST (Skim and make sure you understand the concepts)
• Beginners Guide: http://www.restapitutorial.com/
• Basic Q&A for REST: http://katgleason.tumblr.com/post/37836552900/how-i-explained-rest-to-my-wife
• What are RESTful web services: http://stackoverflow.com/a/3636470/1148249
• What is "CRUD"? http://en.wikipedia.org/wiki/Create,_read,_update_and_delete

Why REST?

• Scalability (dissemination - more people use your API)
• Generality
• Independence
• Latency (Caching)
• Security
• Encapsulation

Verbs

• GET = read an existing record or collection (list of records)
• POST = create and partial update.
• PUT = create and indepotent update (always send all the fields required - not partial update)
• DELETE = does exactly what it says

Examples

• GET /comment - Returns a list of all comments
• GET /comment/:id - Returns a comment with the given id
• POST /comment - Creates a new comment
• PUT /comment/:id - Updates a comment with the given id
• DELETE /comment/:id - Deletes a comment with the given id

Tips

To reduce the amount of data retrieved, we can specify the exact fields we want in url e.g:

GET /accounts/1234/fields=firstname,surname,etc

see: 52:29

Reading / Watching

• What is REST? (if you haven't already read it, read the REST Wikipedia article): http://en.wikipedia.org/wiki/Representational_state_transfer
• The 5 Things Every API Must Have: https://blog.newrelic.com/2014/09/08/apipunchlist/
• Best Practices for Designing a Pragmatic RESTful API (Great article) http://www.vinaysahni.com/best-practices-for-a-pragmatic-restful-api
• REST+JSON API Design - Best Practices for Developers http://youtu.be/hdSrT4yjS1g (comprehensive overview)
• Secure Your API - Tips for REST + JSON Developers http://youtu.be/FeSdFhsKGG0
• PUT vs POST in REST: http://stackoverflow.com/questions/630453/put-vs-post-in-rest

Examples of Successful (Good) APIs

• Parse REST API: https://www.parse.com/docs/rest (really good example of good interactive documentation)
• GitHub: https://developer.github.com/
• Twitter: https://dev.twitter.com/rest/public
• Google: https://developers.google.com/custom-search/json-api/v1/using_rest
• Stripe: https://stripe.com/docs/api

Useful Resources

• lout API documentation generator (for hapi.js apps): https://github.com/hapijs/lout
• RESTful web API Documentation Generator. http://apidocjs.com
• Swagger - The World's Most Popular Framework for APIs: http://swagger.io

Streaming

WebSockets

Reading

• Q: Can we use WebSockets? http://caniuse.com/#feat=websockets
  Answer: YES! IE 10+, Safari/iOS Safari 7.1+, Android 4.4+ & Android Chrome
• About WebSockets: https://www.websocket.org/aboutwebsocket.html
• WebSocket MDN: https://developer.mozilla.org/en/docs/WebSockets
• W3C WebSocket API: http://www.w3.org/TR/2011/WD-websockets-20110419/
• CloudFlare WebSockets (good intro): https://blog.cloudflare.com/cloudflare-now-supports-websockets/
• SitePoint article on WebSockets in HTML5: http://www.sitepoint.com/introduction-to-the-html5-websockets-api/
• Socket.io Chat Example (uses express): http://socket.io/get-started/chat/
• Socket.io Max Connections? 250k: http://stackoverflow.com/questions/10161796/how-many-users-nodejs-socket-io-can-support

Examples

• Twitter Streaming API: https://dev.twitter.com/streaming/overview
• Salesforce Streaming API: http://www.salesforce.com/developer/docs/api_streaming/

Versioning your API?

There is on-going debate on whether APIs should be versioned and if so, how should this be done.

There are two primary approaches to versioning 32:43

Intro Reading

• Your API versioning is wrong: http://www.troyhunt.com/2014/02/your-api-versioning-is-wrong-which-is.html
• The debate on API versioning: http://stackoverflow.com/questions/389169/best-practices-for-api-versioning
• Issues with API version in the URL/URI: https://www.mnot.net/blog/2012/12/04/api-evolution
• Evolving HTTP APIs https://www.mnot.net/blog/2012/12/04/api-evolution

### Wrong way 1 – URL versioning

HTTP GET:
https://haveibeenpwned.com/api/v2/breachedaccount/foo

Wrong way 2 - custom request header

HTTP GET:
https://haveibeenpwned.com/api/breachedaccount/foo
api-version: 2

### Wrong way 3 - content type:

HTTP GET:
https://haveibeenpwned.com/api/breachedaccount/foo
Accept: application/vnd.haveibeenpwned.v2+json

Further Reading (Versioning)

• Pivotal Labs API Versioning guide: http://pivotallabs.com/api-versioning/
• SemVer: http://semver.org/
• Stripe's API Versioning: https://stripe.com/docs/api#versioning
• Comprehensive List of how others are doing versioning: http://www.lexicalscope.com/blog/2012/03/12/how-are-rest-apis-versioned/

Caching

• Caching API Requests: http://robots.thoughtbot.com/caching-api-requests
• Caching your REST API http://restcookbook.com/Basics/caching/
• API Caching http://www.fastly.com/blog/api-caching-part-1/
• Caching and rate limiting: https://blog.apigee.com/detail/api_scalability_part_2_-_caching_rate_limits_and_offloading
• Thoughtbot caching insights (mostly ruby-focussed): http://robots.thoughtbot.com/caching-api-requests

General Background Reading + Watching

• What is an API? (very basic intro): http://youtu.be/B9vPoCOP7oY
• BASIC Introduction to APIs by Derek Dahmer @ General Assembly:
  https://www.youtube.com/watch?v=FknvOGcLHmc (Google for Entrepreneurs - absolute beginner?)
• Wikipedia: http://en.wikipedia.org/wiki/Application_programming_interface
• The REST Cookbook: http://restcookbook.com (comprehensive guide)
• How to Design Great APIs - Parse: https://www.youtube.com/watch?v=qCdpTji8nxo
• How To Design A Good API and Why it Matters: http://youtu.be/heh4OeB9A-c + http://lcsd05.cs.tamu.edu/slides/keynote.pdf (mostly related to the Java Language API but a few general insights)
• Best practices (mostly relating to library APIs not REST/Stream): http://stackoverflow.com/questions/2619854/best-practices-and-guidelines-for-designing-an-api
• Parse interactive API reference: http://youtu.be/qCdpTji8nxo?t=21m15s
• Principals of good RESTful API design: http://codeplanet.io/principles-good-restful-api-design/
• Building Hypermedia APIs with HTML5 and Node: http://www.amazon.com/Building-Hypermedia-APIs-HTML5-Node/dp/1449306578
• Designing APIs for Asynchrony: http://blog.izs.me/post/59142742143/designing-apis-for-asynchrony
• API Design Principles: http://qt-project.org/wiki/API-Design-Principles (general principals. ignore the QT-specific parts)