Project Logistics

• http://sourceforge.net/projects/lighttracker
• Beta Status
• SVN coming soon
• database schema: db.sql
• main source code: lightTracker.py
• wrapper: runserver.py
• automated integration test: testtracker.py
• A quick demo
• Contribution is encouraged. (CSDN competition?)

BitTorrent 101: Components

• peers
• torrent file
• seeding
• tracker
• True P2P with DHT

BitTorrent 101: Scenario

1. create .torrent file
2. initial seeding
3. peers contacts tracker
4. inter-peer communication
5. seeding after completion

Tracker Protocol Specification

• Recommended: Technical Specification
• Official Protocol Specification
• Announce: info_hash, peer_id, port, status, and downloaded
• Scrap: info_hash
• bencode: Python specification encoding spec

Why lightTracker

• Not scalable: local pickled file.
• Twisted based: powerful but difficult to understand
• Tracker is a typical web application
• Which web framework then?
• web.py: one single very light web framework.
• django: great community support. comprehensive.
• We choose web.py because easy to deploy and its lightweight nature.

web.py 101

• Three fundamental elements:
1. How data is retrieved and passed around.
2. How presentation layer works with data.
3. How URL, cookie, and session are supported.
• web.py's 'Pythonic' answer:
1. lightweight database gateway and the magic storify
2. HTML based "cheetah" template, bound with objects
3. Thinnly wrapped via storify objects.

Code Walkthrough

• database schema
• runserver.py
• lightTracker.py
1. Section: Book keeping
2. Section: Prepare response
• testtracker.py: unittest based.
1. class MetaInstruction
2. _status_assertion (idea to make it less verbose?)

Questions?