Django и HTTP-кэширование

Ринат Хабибиев (zvooq.com, ведущий разработчик) @ Moscow Python Conf 2017
"Много лет работая с Django, мне часто приходилось дорабатывать встроенные решения, либо заменять их на свои собственные реализации. На встрече речь пойдёт о механизме HTTP-кэширования Django, об эффективном его использовании и о том, как сделать этот инструмент ещё более эффективным, устранив в нем несколько проблем и добавив новых возможностей. Заодно, разберём лучшие практики HTTP-кэширования и попробуем решить главнейшую проблему в программировании - инвалидацию кэша".
Видео: https://conf.python.ru/django-and-http-cash/

Transcript

1. Django: HTTP-cache Developer’s guide Rinat Khabibiev, 2017
2. RINAT KHABIBIEV 2 https://github.com/renskiy https://www.facebook.com/rinat.khabibiev PostgreSQL
3. Музыкальный сервис для массовой аудитории
4. HTTP-CACHE • What is it • How it works • Cache management • Django HTTP tools
5. SERVER-SIDE CACHE HTML JSON XML …
6. CLIENT-SIDE CACHE
7. ALL CACHES (HTTP-CACHING)
8. CACHEABLE REQUESTS AND RESPONSES GET HEAD POST RFC 7231 HTTP 1.1: Semantics and Content Requests 200 203 204 300 301 404 405 410 414 501 Responses
9. SERVER-SIDE CACHE MANAGEMENT
10. SERVER-SIDE CACHE MANAGEMENT Expires: Tue, 31 Jan 2012 15:02:53 GMT Last-Modified: Mon, 30 Jan 2012 15:02:53 GMT ETag: W/"56d-9989200-1132c580" Cache-Control: public, max-age=86400 Age: 3600 Vary: Cookie, Accept-Language
11. CLIENT-SIDE CACHE MANAGEMENT
12. CLIENT-SIDE CACHE MANAGEMENT If-Modified-Since: Tue, 31 Jan 2012 15:02:53 GMT If-Unmodified-Since: Tue, 31 Jan 2012 15:02:53 GMT Pragma: no-cache Cache-Control: max-age=30 If-None-Match: W/"56d-9989200-1132c580" If-Match: "56d-9989200-1132c580" If-Range: "56d-9989200-1132c580"
13. DJANGO HTTP-CACHING: MIDDLEWARES # settings.py MIDDLEWARE = [ ‘django.middleware.http.ConditionalGetMiddleware', 'django.middleware.cache.UpdateCacheMiddleware', 'django.middleware.common.CommonMiddleware', 'django.middleware.cache.FetchFromCacheMiddleware', ] CACHES = { 'default': { 'BACKEND': 'django.core.cache.backends.locmem.LocMemCache', }, } CACHE_MIDDLEWARE_ALIAS = 'default' CACHE_MIDDLEWARE_SECONDS = 600 CACHE_MIDDLEWARE_KEY_PREFIX = ''
14. DJANGO HTTP-CACHING: DECORATORS from django.utils import timezone def get_last_modified(request: HttpRequest, *args, **kwargs): return timezone.now() def get_etag(request: HttpRequest, *args, **kwargs): return "56d-9989200-1132c580" @cache_page(600, cache='default', key_prefix='') @last_modified(get_last_modified) @etag(get_etag) def my_view(request: HttpRequest, *args, **kwargs): return HttpResponse()
15. DJANGO HTTP-CACHING # settings.py MIDDLEWARE = [ 'django.middleware.cache.UpdateCacheMiddleware', ... 'django.middleware.cache.FetchFromCacheMiddleware', ]
16. HTTP/1.1 200 OK Date: Sun, 01 Jan 2017 00:00:00 GMT Expires: Sun, 01 Jan 2017 02:00:00 GMT Cache-Control: max-age=7200 Client #1 makes request at 00:00 AM HTTP/1.1 200 OK Date: Sun, 01 Jan 2017 00:01:00 GMT Expires: Sun, 01 Jan 2017 02:00:00 GMT Cache-Control: max-age=7200 Age: 3600 Client #2 makes request 1 hour later and gets response from cache This makes cache expiration at 03:00, not at 02:00 DJANGO HTTP-CACHE: MAX-AGE BUG
17. DJANGO HTTP-CACHING WITH CONDITIONAL REQUESTS
18. DJANGO HTTP-CACHING WITH CONDITIONAL REQUESTS
19. Sets header "Vary: Cookie" DJANGO HTTP-CACHE: VARY HEADER BUG
20. DJANGO HTTP-CACHE: VARY HEADER BUG HTTP/1.1 200 OK Date: Sun, 01 Jan 2017 00:00:00 GMT Expires: Sun, 01 Jan 2017 02:00:00 GMT Cache-Control: max-age=7200 Vary: Cookie Authorised client makes request for private data HTTP/1.1 200 OK Date: Sun, 01 Jan 2017 00:01:00 GMT Expires: Sun, 01 Jan 2017 02:00:00 GMT Cache-Control: max-age=7200 Another authorised client makes request later and gets response generated for another user!! Actual and very critical when using @cache_page (bug #15855) Set by SessionMiddleware after response was saved to cache
21. @cache_page(600) @vary_on_headers('Cookie', 'Accept-Language') def my_view(request: HttpRequest, *args, **kwargs): return HttpResponse() DJANGO HTTP-CACHE: VARY HEADER BUG FIX (FORCED)
22. DJANGO: CACHE INVALIDATION from django.utils.functional import lazy def get_key_prefix(): return 'v1' @cache_page(600, key_prefix=lazy(get_key_prefix, str)()) def my_view(request: HttpRequest, *args, **kwargs): return HttpResponse() threading.local() can be used to access current request
23. DJANGO HTTP-CACHE Not too hard, isn’t it?
24. DJANGOCACHE pip install django-cache from djangocache import cache_page def get_etag(request: HttpRequest, *args, **kwargs): return "56d-9989200-1132c580" @cache_page(cache_timeout=600, key_prefix=get_etag) @etag(get_etag) def my_view(request: HttpRequest, *args, **kwargs): return HttpResponse() • No middlewares needed • Works with Django >= 1.8 • Fixed Django cache bugs • Callable ‘key_prefix’ for cache invalidation • Callable ‘cache_timeout’ • Cache max-age can be limited by client https://github.com/renskiy/django-cache
25. LINKS & THANKS • RFC 7231 HTTP/1.1: Semantics and Content • RFC 7232 HTTP/1.1: Conditional Requests • RFC 7234 HTTP/1.1: Caching • https://www.djangoproject.com Thanks!