1. Apache
CouchDB

2. Relax

3. Hello
• J Chris Anderson
• Apache CouchDB committer
• Web programmer (Rails, Ajax, etc)
• Director, couch.io

4. About You?
• Web developers are easy
• Scalable key/value store
• Peer-based Replication
• Append-only IO pattern

5. Scaling Up
• Hot. Literally.
• You don’t have to think.

6. X
Scaling Up
• Hot. Literally.
• You don’t have to think.

7. Scale Enforces Constraints
• Distributed key / value stores
• Context is expensive
• No joins or autoincrement
• Eventual consistency

8. e Web Scales

9. Why CouchDB?
Native to the Web
Scale from a cluster to a smartphone
Local data == low latency
Replicated applications - the p2p web

10. Of the Web
Let me tell you something: Django may be built
for the Web, but CouchDB is built of the Web.
I've never seen software that so completely
embraces the philosophies behind HTTP. ... this
is what the software of the future looks like.
Jacob Kaplan-Moss
October 19, 2007
http://jacobian.org/writing/of-the-web/

11. JSON
HTTP
Local
Robust

12. JSON Documents
{
"_id": "BCCD12CBB", Schema Free
"_rev": "1-AB764C",
"type": "person",
"name": "Darth Vader",
Self-Contained
"age": 63,
"headware":
["Helmet", "Sombrero"], JavaScript Map
}
"dark_side": true
Reduce Views

13. Map Reduce Views
Docs
{ “user” : “Chris”,
Map
{ “key” : “Alice”, “value” : 5 }
“points” : 3 } { “key” : “Bob”, “value” : 7 }
{ “user” : “Joe”, function(doc) { { “key” : “Chris”, “value” : 3 }
“points” : 10 } if (doc.user && doc.points) { { “key” : “Joe”, “value” : 10 }
{ “user” : “Alice”, emit(doc.user, doc.points); { “key” : “Mary”, “value” : 9 }
“points” : 5 } }
{ “user” : “Mary”, }
“points” : 9 }
{ “user” : “Bob”, Reduce
“points” : 7 }
Alice ... Chris: 15
function(keys, values, rereduce) { Everyone: 34
return sum(values);
}

14. JavaScript Map Reduce

16. ful 
You already know the API
Use existing HTTP tools
Talk directly to the browser

17. ful 
CRUD
• Create
HTTP PUT /db/mydocid
• Read
HTTP GET /db/mydocid
• Update
HTTP PUT /db/mydocid
• Delete
HTTP DELETE /db/mydocid

18. Local Data
Low latency (fast)
Peer-based incremental replication
View source --> Open source

19. Gives Control to Users
CC-BY-SA http://www.flickr.com/photos/kelleys/492253912/

20. Robust Storage
Append Only
File Structure
Designed to Crash
Instant-On

21. Happy IO Patterns

22. Bandwidth Explosion

29. “no bars”

30. http://www.flickr.com/photos/hercwad/2290378571/

32. http://www.flickr.com/photos/mcpig/872293700/

33. Latency Sucks

34. Scaling Down
4 MB RAM

35. Erlang
Parallel
Fault tolerant
Addictive
Ninja Syntax http://www.sics.se/~joe/apachevsyaws.html

36. Browser Couch
JavaScript port
Uses HTML5 storage
Replicates with CouchDB
http://hg.toolness.com/browser-couch/

37. No SQL
in
HTML5

38. Incremental Replication

39. curl -X POST http://127.0.0.1:5984/_replicate -d
'{"source":"http://couch.example.com:5984/remote-db",
"target":"local-db"}'

40. curl -X POST http://127.0.0.1:5984/_replicate -d
'{"source":"http://couch.example.com:5984/remote-db",
"target":"local-db"}'

52. Document Oriented
Not Relational
• Documents in the Real World™
• Bills, letters, tax forms…
• Same type != same structure
• Self contained
• Can be out of date (so what?)
• No references

53. Document Oriented
Not Relational
• Documents in the Real World™
Bills, letters, tax forms…
Natural Data
•
• Same type != same structure
•
Behaviour
Can be out of date (so what?)
• No references

58. Render JSON Docs as HTML
shows/post.js /drl/_design/sofa/_show/post/Hello-World-For-Real-This-Time

60. Render Views as HTML
lists/index.js /drl/_list/sofa/index/recent-posts?descending=true&limit=8

69. Resources
@CouchDB
http://couchdb.apache.org/
Dress like a Couch: http://shop.couchdb.com
http://planet.couchdb.org/
https://peepcode.com/products/couchdb-with-rails

70. @couchdbinaction
http://books.couchdb.org/relax

71. couch.io
Berlin – London – Portland

72. anks!

73. CC-by-nd http://www.flic.kr/photos/eifelyeti110/273939759/