This document provides an introduction and overview of CouchDB including: - Background on the creators and history of CouchDB's development - An explanation of how CouchDB differs from traditional SQL databases through its use of RESTful HTTP, schemaless JSON documents, map/reduce views, and incremental replication - A description of CouchDB's internal architecture and key modules - An invitation for readers to get involved with the CouchDB community

2. Hello
• Chris Anderson <jchris@apache.org>
• Blog: http://jchris.mfdz.com
• Founder, Grabb.it (web analytics for music)
• Ruby on Rails veteran
• CouchDB committer

3. And You?
• Used CouchDB (for fun)
• Evaluating or using it (for a project)
• Interested in contributing?
• Just here for the pizza?

4. History
• Damien Katz <http://damienkatz.net/>
• Worked on Lotus Notes & MySQL
• Started in 2005: C++ and XML, on Windows
• 2006: Moved to Erlang, JSON, and POSIX
• 0.7.0 first release of today’s CouchDB
• Version 1.0 Planned for the end of 2008

5. Why CouchDB?
• Common use cases no longer fit RDBMS
• Native to web applications
• Peer-based replication for freedom
• Takes today’s scalability lessons to heart

6. This Talk
• How is CouchDB different (from RDBMS)?
• Example HTML/Javascript application
• Quick tour of the internals

7. How Is CouchDB Different?
RESTful HTTP
Schemaless JSON Documents
Map/Reduce Views
Incremental Replication

8. How Is CouchDB Different?
(from SQL RDBMS)
RESTful HTTP
Binary Protocol
Schemaless JSON Documents
Typed Columns & Primary Keys
Map/Reduce Views
Ad-hoc Queries
Incremental Replication
Replication Logs

9. RESTful HTTP
Built for the web
Javascript Test Suite
Standard HTTP Clients,
Proxies, Load Balancers & Caches

10. RESTful HTTP
Built for the web
Enterprisey
Javascript Test Suite
Battle Hardened
Standard HTTP Clients,
Proxies, Load Balancers & Caches
Protocol Specific Tools

11. Schemaless JSON
Documents
Flat Namespace
Arbitrary JSON Structures
Identified By URIs
Optimistic Locking (ACID/MVCC)

12. Schemaless JSON
Documents
Flat Namespace
Tables
Arbitrary JSON Structures
Typed Columns and Key Constraints
Identified By URIs
Primary Keys
Optimistic Locking (ACID/MVCC)
Row or Column Level Locking

13. Map/Reduce Views
Functional Javascript
Incremental Updates
Predefined
High-Performance Reads

14. Map/Reduce Views
Functional Javascript
SQL Statements
Incremental Updates
Independent
Predefined
Ad-hoc and Complex
High-Performance Reads
Indexes Computed on Writes

15. Incremental Replication
User Triggered
Offline Clients
Resilient & Restartable
HTTP

16. Incremental Replication
User Triggered
Continuous
Offline Clients
Master/Slave
Resilient & Restartable
Critical Path
HTTP
Log Based

17. CouchDB
A new way to write web applications.
HTML / Javascript
_design Documents
p2p Replication

18. Live Code!
http://169.254.251.59:5984/_utils/

19. CouchDB Internals
• couch_httpd.erl
• Request Dispatch
• Create Database
• Get Document
• Other Modules

20. Request Dispatch

21. Create Database

22. Get Document

23. Other Modules
• couch_btree.erl
• The heart of the storage module (stores
Erlang terms sorted by key using user
specified sort funtions)
• couch_db_updater.erl
• Translates document requests into Btree
actions.
• couch_query_servers.erl
• Communicates with the external
(Javascript etc) view servers.

24. Join Us
• #couchdb on irc.freenode.net
• http://couchdb.org
• mailing lists
• links to wiki and subversion checkout

25. Thank You!
Any Questions?