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I am using(trying) redis as a cache to my django app. This is how I am trying to do it.

def postview(request):
    post_list = []
    if cache.get("posts") == None:
           post_list = Post.objects.all()
           cache.set("posts", post_list, timeout=None)
    else : 
           post_list = cache.get("posts")
    context = {"post_list" : post_list}
    return render(request, 'post_list.html', context)

@cache_page(60*15, key_prefix="test_cache")
def new(request):
    print("testing")
    return HttpResponse("hello, I am mohammed")

This is the output in redis-cli

luvpreet@DHARI-Inspiron-3542:~/test_venv_wrapper/test_redis$ redis-cli
127.0.0.1:6379> select 2 # I have redis db 2 as backend in django settings
OK
127.0.0.1:6379[2]> keys *
1) ":1:views.decorators.cache.cache_page.cache_test.GET.26488770af116d67b33750e5f304aa3e.d41d8cd98f00b204e9800998ecf8427e.en-us.UTC"
2) ":1:views.decorators.cache.cache_header..d314df08d6409ed165873dfa23271c50.en-us.UTC"
3) ":1:posts"
4) ":1:views.decorators.cache.cache_page..GET.d314df08d6409ed165873dfa23271c50.d41d8cd98f00b204e9800998ecf8427e.en-us.UTC"
5) ":1:views.decorators.cache.cache_header..26488770af116d67b33750e5f304aa3e.en-us.UTC"
6) ":1:views.decorators.cache.cache_page..GET.26488770af116d67b33750e5f304aa3e.d41d8cd98f00b204e9800998ecf8427e.en-us.UTC"
7) ":1:views.decorators.cache.cache_header.cache_test.26488770af116d67b33750e5f304aa3e.en-us.UTC"

This is the value under one of the keys,

127.0.0.1> get :1:views.decorators.cache.cache_page.cache_test.GET.26488770af116d67b33750e5f304aa3e.d41d8cd98f00b204e9800998ecf8427e.en-us.UTC
"\x80\x02cdjango.http.response\nHttpResponse\nq\x01)\x81q\x02}q\x03(U\x0e_handler_classq\x04NU\b_headersq\x05}q\x06(U\rlast-modifiedU\rLast-ModifiedU\x1dWed, 05 Apr 2017 10:56:58 GMT\x86U\aexpiresU\aExpiresU\x1dWed, 05 Apr 2017 15:06:58 GMT\x86U\x0ccontent-typeU\x0cContent-TypeU\x18text/html; charset=utf-8\x86U\rcache-controlU\rCache-ControlU\rmax-age=15000\x86uU\b_charsetq\aNU\x11_closable_objectsq\b]U\acookiesq\tcdjango.http.cookie\nSimpleCookie\nq\n)\x81q\x0b}q\x0cbU\x06closedq\r\x89U\n_containerq\x0e]q\x0fU\x14Hello, I am Mohammedq\x10aU\x0e_reason_phraseq\x11Nub."

This is some serialized value.

The queryset Post.objects.all() is cached and I have no problem in getting this from cache. But I am failing to understand this @cache_page() decorator.

Why is it making so many keys in the redis database ? Please explain the keys made in the redis database. How can I get to know this is working or not ?

4

1 回答 1

2

cache_pagedecorator 是 django 装饰器，而不是 django-redis 装饰器。所以，如果你在 django 中使用像 memcached 这样的默认缓存，cache_page 装饰器会在 memcached 中创建相同的键。这是文档字符串中的装饰器基本代码：

https://github.com/django/django/blob/711123e1cdaf3b08c876c045d8d38decdc7a63d3/django/views/decorators/cache.py#L8

""" 视图的装饰器，用于尝试从缓存中获取页面并在页面尚未在缓存中时填充缓存。缓存由 URL 和一些来自标头的数据作为键。此外，还有键前缀用于区分多站点设置中的不同缓存区域。例如，您可以使用 get_current_site().domain，因为它在 Django 项目中是唯一的。此外，响应的 Vary 标头中的所有标头都将被考虑在内关于缓存——就像中间件一样。"""

因此，它本质上是创建多个键，一个用于标头，另一个用于 HTTPResponse 内容。它基于标头和内容创建键，因此标头中的任何更改都会使缓存无效（例如，在不同标头的情况下），即即使 url 中的参数相同，但请求标头中的内容不同，您将拥有单独的缓存. 不同请求标头的示例可以是为不同的登录用户发送有关同一页面的登录信息，或者根据标头中存在的移动/桌面用户代理信息为相同的 url 提供不同的内容。这是django中的缓存键代码：

def _generate_cache_key(request, method, headerlist, key_prefix):
    """Return a cache key from the headers given in the header list."""
    ctx = hashlib.md5()
    for header in headerlist:
        value = request.META.get(header)
        if value is not None:
            ctx.update(force_bytes(value))
    url = hashlib.md5(force_bytes(iri_to_uri(request.build_absolute_uri())))
    cache_key = 'views.decorators.cache.cache_page.%s.%s.%s.%s' % (
        key_prefix, method, url.hexdigest(), ctx.hexdigest())
    return _i18n_cache_key_suffix(request, cache_key)


def _generate_cache_header_key(key_prefix, request):
    """Return a cache key for the header cache."""
    url = hashlib.md5(force_bytes(iri_to_uri(request.build_absolute_uri())))
    cache_key = 'views.decorators.cache.cache_header.%s.%s' % (
        key_prefix, url.hexdigest())
    return _i18n_cache_key_suffix(request, cache_key)


def get_cache_key(request, key_prefix=None, method='GET', cache=None):
    """
    Return a cache key based on the request URL and query. It can be used
    in the request phase because it pulls the list of headers to take into
    account from the global URL registry and uses those to build a cache key
    to check against.
    If there isn't a headerlist stored, return None, indicating that the page
    needs to be rebuilt.
    """
    if key_prefix is None:
        key_prefix = settings.CACHE_MIDDLEWARE_KEY_PREFIX
    cache_key = _generate_cache_header_key(key_prefix, request)
    if cache is None:
        cache = caches[settings.CACHE_MIDDLEWARE_ALIAS]
    headerlist = cache.get(cache_key)
    if headerlist is not None:
        return _generate_cache_key(request, method, headerlist, key_prefix)
    else:
        return None
于 2017-04-09T19:07:07.363 回答