The document discusses strategies for achieving high availability in Django applications, emphasizing the importance of monitoring, profiling, and performance optimization techniques. It recommends tools for query optimization and caching, as well as robust hardware and infrastructure practices for handling requests. The document also compares mod_wsgi and uwsgi, highlighting their respective advantages and community support.

1. High-Availability Django
Frankie Dintino
The Atlantic

4. Performance woes…

5. …and crises

6. Today

7. First steps
• Monitoring and profiling: understand your
bottlenecks
• Tackle the “easy” stuff first: query optimization,
caching
• Don’t neglect front-end performance

8. Profiling
• Hosted services: New Relic, Opbeat
• django-debug-toolbar, django-silk
• cProfile / pyprof2calltree / KCacheGrind for
masochists
• WSGI middleware

9. Monitoring
• Downtime notifications: Alertra, New Relic,
Opbeat, Chartbeat
• Nagios and its many forks, Zabbix

10. Caching
• Use a CDN
• Proxy cache (Nginx, Squid, Varnish)
• {% cache %}, @cached_property,
CachedStaticFilesStorage, cached template
loader
• Page caching frameworks
• ORM caching: a mixed bag

11. Query optimization
• .prefetch_related(), .select_related()
• prefetch_related_objects() for generic
foreign keys
• .values() and .values_list() where it
counts, if possible
• Database parameter tuning, judicious indexing

12. Throwing more hardware at the
problem also works.

13. “Request Queuing?”

14. “Request Queuing?”

15. theatlantic :4000
citylab :5000
admin :6000
:80

16. upstream theatlantic {
server apps1:4000;
server apps2:4000;
server apps3:4000;
}
upstream citylab {
server apps1:5000;
# ...
}

17. upstream theatlantic_stage {
server apps1:4500;
server apps2:4500;
server apps3:4500;
}
upstream citylab_stage {
server apps1:5500;
# ...
}

18. /www/site/
stage/
live/
a/
b/

19. /www/site/
stage/
live/
a/
b/

20. Basic principles
• “a” and “b” repositories are always “production-
ready.”
• Force as much Django code to load as possible
before defining def application() in your
WSGI file.
• Before swapping the upstreams, “warm up” the
workers with concurrent HTTP requests.

21. mod_wsgi vs. uWSGI

22. mod_wsgi
• In general, comparable performance
• Runs on Apache HTTP server
• Mostly the work of a single developer
• Documentation terminally out-of-date
• Important configuration options missing or only
discoverable in the release notes

24. uWSGI
• Broad and active community
• Very thorough documentation (overwhelming, in
fact)
• Highly configurable

31. github.com/hadjango
@frankiedintino
frankie@theatlantic.com

32. High-Availability Django