Caching - A Primer

Transcript

1. Caching and Django A Primer @ashchristopher

2. What is a Cache?

3. Temporary storage of non-complex data

4. Provides very fast lookups

5. Django supports simple caching

6. Django includes support for a number of cache backends out-of-the-box

7. Memcache cluster of Memcache servers Database cache uses database table

   for cache Filesystem cache file on the local filesystem Local memory cache only good for local development

8. Easy to make your own cache backend

9. Extend core.cache.backends.base.BaseCache

10. Simple caching follows the same pattern

11. 1. Check the cache for data and if found, return

    it 2. If data is not in cache - get data from the database, put data in cache then return the data 3. Invalidate cache on data change.

12. Your system works even if your cache is offline

13. Some cool projects/apps to help you with it

14. Django Middleware (per-site and per-view)

15. Cache Machine

16. Johnny-Cache

17. None

18. Low-level Caching (doing it by hand)

19. Caching is simple...

20. ... except when it isn’t!

21. Cache invalidation is hard

22. Cache invalidation is especially hard at scale

23. What happens when an expensive operation falls out of cache?

24. Thundering Herd

25. Fundamental flaw?

26. I think so!

27. Caching doesn’t mean what it used to mean

28. What you want is probably not caching

29. Denormalized Data

30. Actively set new data instead of letting things fall out

    of cache

31. Nothing falls out of cache

32. Set your data via asynchronous processes

33. None

34. No Silver Bullet

35. Optimizing read speed by adding redundant data

36. Persistent storage

37. NoSQL

38. There is a problem with denormalized data at scale

39. Denormalized data becomes a requirement

40. What problem?

41. Embrace denormalized data

42. @ashchristopher ash.christopher@gmail.com