Who Am I?
• Chris Anderson <jchris@apache.org>
• CouchDB committer
• Blog: http://jchrisa.net

Couch History
• Damien Katz <http://damienkatz.net/>
• Worked on Lotus Notes & MySQL
• Started CouchDB in 2005
• 2006: Moved to Erlang, JSON and JavaScript
• Approaching 0.9 Release

2008 Erlang User of the Year

This Talk
• Hello CouchDB
• Hands on with CouchApp
• The Future
• Get Involved

Hello CouchDB
• JSON Documents
• HTTP / REST (You already know the API)
• ACID Storage Engine
• Map Reduce Views
• Replication for Freedom
• Portable Standalone Applications

JSON Documents
{“json” : “key / value pairs”,
“_id” : “some uuid”,
“_rev” : “mvcc key”,
“string keys” : [1,2,3,”four”,null],
“schema free” : true}
Your programming
language supports JSON.

JSON Documents
{“json” : “key / value pairs”,
“_id” : “some uuid”,
“_rev” : “mvcc key”,
“string keys” : [1,2,3,”four”,null],
“schema free” : “flexible”}
Adapt data as your
application changes.

HTTP / CRUD
You already know the API.
GET read
PUT create or update
DELETE delete
POST bulk operation

ACID Storage Engine
• Append Only
• Multi Version Concurrency Control
• B-Tree Indexes O(log n)
• Attachment Streaming
Oooh, self-similar

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

Peer-Based Replication
for Freedom
Triggered
Incremental
Filtered*

Let’s Replicate
Everything!
• Take full advantage of CouchDB
• View-source Open Source
• The Future is Distributed

But that’s not RESTful!
Representational State Transfer...
it’s more than just verbs,
it’s the hyperlinks.
Webpage
Webpage Webpage
Webpage
∴
We need HTML.

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

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

Hands On with CouchApp
• CouchApp is just some filesystem helpers
• Embodies “best practices”
• CouchApp is not opinionated, CouchDB is.
• Don’t shoot the messenger.

Install CouchApp
sudo easy_install couchapp
or
git clone git://github.com/jchris/couchapp.git

Check Your CouchDB
http://127.0.0.1:5984/_utils/

Setup Credentials
Leaky Abstraction!
edit:
/usr/local/etc/couchdb/local.ini
add:
[admins]
username = secretpassword

Get the Example App
(ajax version)
couchapp clone
http://jchrisa.net/sofa-ajax/_design/sofa
cd sofa
couchapp push
http://user:pass@localhost:5984/sofa-ajax

The Guts

First Post!

Firebug to see requests

Upgrade to real HTML
couchapp clone
http://jchrisa.net/drl/_design/sofa
cd sofa
couchapp push
http://user:pass@localhost:5984/sofa

How’s it Work?
Macros so functions
can be in multiple files.

Templating

The Future
• Key-Centric Identity?
• P2P Topologies don’t leave room to trust
the server.
• Multi-Node clusters
• High performance, large databases

Resources
• #couchdb and #couchapp on
irc.freenode.net
• http://couchdb.apache.org for mailing lists
• http://planet.couchdb.org/
• http://books.couchdb.org/relax/
• Twitter search for “couchdb”

Thank You!