Simon Willison: Ajax and the Flickr API

• Flickr: totally buzzword compliant (“Social software, Tags/Folksonomies, Web Services, Ajax”)
• The developers said: “we wouldn’t trust a service with no export option”
• Don’t want to build an export tool
• Built an API instead – let the users build an export tool
• No-one’s built one yet, though they have built loads of other cool things
• Related tags browser
• Flickr upload tools: iPhoto plugin; various Linux ones; FlickrFS – virtual filesystem for Linux!
• The ultimate geo-spatial mashup! magic tags in photos: geo-long, geo-lat, geotagged XXX

Web services
* Lets software talk to other software over the web
* SOAP and XML-RPC – magic function calls
* REST
* Flickr API calls made by sending named parameters to an endpoint
* Required: method, api_key
* All data is expected to be UTF-8, if not, it’s converted from iso-8859-1
* Public, private and authentication-dependent methods
* API Explorer
* Community API kits in various languages

Scrümjax! (Flickr’s own buzzword)
* Inline editing – titles, descriptions, tags
* Notes
* Misc. niceties
* All uses the public web services API!! (Martin: this is SOA on speed…)
* They’re eating their own dogfood
* Firefox LiveHttpHeaders extension is useful for debugging Ajax apps.

Benefits of adding web services to apps
* User trust
* External innovation & creativity
* Encourages better app design
* XMLHttpRequest and REST make a great combination
* www.flickr.com/services/
* If you only want read-only, there are also RSS feeds

Audience questions
* What percentage of usage is via the API? Not sure, but Flickr is the biggest user of its own API.
* How much load is introduced by exposing the API? Absolutely loads, as some queries are really expensive.
* How has the API design evolved? Simon’s only been there three weeks, but he thinks the API has been there from very early on.
* Server-side tech? PHP/MySQL (!). Loads of caching used, plus some java to distribute photos between servers. Performance-intensive stuff in C/C++.
* Organizr uses the API? Yes, but the XML-RPC version.
* What stops someone building their own site on top? API keys, and Ts&Cs