The document discusses Redis usage at Guardian.co.uk and for a Soulmates architecture. Redis is used to track reviewed articles, count requests and SQL operations in Django, and implement management switches across processes and servers without a centralized database. Switches can be toggled from any server or process by hitting a URL, and all processes can later check the switch value stored in Redis.

1. REDIS AT GUARDIAN.CO.UK
Michael Brunton-Spall - @bruntonspall

2. MPS’ EXPENSES (2)

3. MPs’ Expenses 2

4. Before Redis
Originally selected a random article to start reviewing
SQL = ORDER BY RAND() LIMIT 1
Inefficient and horrible

5. If in doubt, ask

6. With Redis
Maintain redis set of all available pages per assignment
Maintain redis set of reviewed pages per assignment
SDIFFSTORE the two sets
Use SRANDMEMBER on the stored set

7. SDIFFSTORE

8. SRANDMEMBER

9. SOULMATES

10. Soulmates

11. What do we use it for?
github.com/simonw/django-redis-monitor
Written internally by Simon Willison and Daniel Vydra
Counts requests per second / SQLops per second in django
Management switches

12. Management Switches
Whats the problem?
We’re basically a java shop
In Java, management switches are easy
In python not so much

13. How Java Works

14. How Python Works

15. Soulmates Architecture
Django Django
Frontend Frontend
Redis Redis
Scala API Scala API Solr Slave
Solr Slave
WebApp WebApp
Solr Master
MongoDB
MongoDB

16. Switches must be externalised
Normally we’d use the database but
Soulmates django app doesn’t have a database
So we used redis

17. Define and initialise

18. Implementation

19. Redis Switches
Hit a URL on any server, any process to toggle switch
All processes are able to check that switch later
Redis processes are local to the machine