1. Embeddable Discussions Ivelin Elenchev

2. Project Goal
Provide easy to configure discussions using <iframe>
Advanced configurable discussions using a web based API

3. Forums

4. Website Comments

5. Ecommerce reviews

6. System Level Requirements
The system should be able to recognize discussion hosting websites and applications and return the requested information
The system should be able to filter malicious requests via user activity, browser signature and IP
The system should be able to monitor its resource usage and automatically reconfigure the storage and application cluster as needed

7. Moderator Level Requirements
Administrators should be able to specify the discussion type (hierarchical, rating, review)
Administrators should be able to specify custom discussion templates
Administrators should be able to moderate discussions and assign privileges to users
Administrators should be able to view usage statistics

8. User Level Requirements
Users should be able to comment and reply to others
Users should be able to log in from third party services via authentication tokens
Users should be able to rate and flag other comments
Users should be able to receive push & notifications in special events (reply, rating, achievment)

9. Requirements
Administrators should be able to specify the discussion type (hyrarchial, rating, review)
Users should be able to comment and reply to others
Users should be able to log in from third party services via authentication tokens
Users should be able to rate and flag other comments
Administrators should be able to specify custom discussion templates

10. Performance Requirements
The system architecture should allow for cheap horizontal scaling
The system should be able to function under high levels of IO (IO bound not CPU bound)
Crashes in parts of the database or application clusters should not affect the rest of the system

11. Roadmap ✅ Storage “schema” + cluster configuration ✅ Storage caching
✅ User API
Administrator API
System API
API Cluster configuration + monitoring
Application Caching

12. Storage
Postgres pros: battle tested, consistency (transactions) cons: partitioning relies on a master node, querying hirarchial comment data is slow (at least 2 joins)
Cassanda: pros: reliable scaling, fault tolerant, performance under high IO cons: query language

13. Storage Caching
Redis queries to Cassandra for the last minute are storedd in Redis. Cassandra is hit only if the Redis cache is too old, or does not exist. Non-priority users always get the Redis cache

14. Application
Python pros: asynchronous web frameworks (Tornado), community cons: heavy system threading model
Erlang / Elixir pros: asynchronous web framework (Phoenix), light VM threads, application cluster support cons: community

15. Webserver Architecture
Nginx reverse proxy, static file caching, access limitation
Cowboy Erlang webserver dealing with WSGI requests
Varnish Cache API request caching

16. Questions?