Getting the most out of Varnish (DrupalCamp Galway 2014)

Best practices for tuning cache configuration
Recording: https://www.youtube.com/watch?v=u0G6PUe-n30&feature=youtu.be

1. Getting the most out of Varnish
2. Basics • Reverse HTTP caching proxy • Load balancing • High performance • No SSL • Avoids "Thundering herd" • Caching logic in VCL
3. Setup
4. Configure sane resource limits • cache memory • thread_pools • threadpoolmin, threadpoolmax
5. Caching logic
6. vcl_recv • Normalize and rewrite client input • Pick a backend web server • Decide caching policy • Access control
7. Enable grace mode
8. Drop unnecessary cookies
9. Force pass for sensitive URLs
10. vcl_hash • Defines what is unique about a request. • Executed directly after vcl_recv
11. Do not Vary on User- Agent
12. vcl_hit • Right after an object has been found (hit) in the cache • You can change the TTL or issue purge • Often used to throw out an old object
13. vcl_miss • Right after an object was looked up and not found in cache • Mostly used to issue purge • Can also be used to modify backend request headers
14. vcl_pass • Run after a pass in vcl_recv or after a lookup that returned a hitpass • Not run after vcl_fetch
15. vcl_fetch • Sanitize server response • Override cache duration
16. Understand hit_for_pass
17. vcl_deliver • Common last exit point for all (except vcl_pipe) code paths • Often used to add and remove debug-headers
18. Application
19. Use Far Future Expiration
20. Operation
21. Monitor KPI • cache_hit • cache_miss • backend_fail • backend_toolate • lru_nuked
22. Monitor syslog
23. Questions?
24. Thanks! • Sad Cookie by Hey Paul Studios, on Flickr