Django缓存视图
一、今日学习内容概述
| 学习模块 | 重要程度 | 主要内容 |
|---|---|---|
| 视图缓存基础 | ⭐⭐⭐⭐⭐ | 缓存装饰器、缓存配置 |
| 基于会话缓存 | ⭐⭐⭐⭐⭐ | 会话存储、用户相关缓存 |
| 动态缓存处理 | ⭐⭐⭐⭐ | 条件缓存、缓存失效 |
| 缓存优化策略 | ⭐⭐⭐⭐ | 性能优化、最佳实践 |
二、缓存配置示例
# settings.py
CACHES = {'default': {'BACKEND': 'django.core.cache.backends.redis.RedisCache','LOCATION': 'redis://127.0.0.1:6379/1','OPTIONS': {'CLIENT_CLASS': 'django_redis.client.DefaultClient','PARSER_CLASS': 'redis.connection.HiredisParser','CONNECTION_POOL_CLASS': 'redis.connection.BlockingConnectionPool','CONNECTION_POOL_CLASS_KWARGS': {'max_connections': 50,'timeout': 20,}}},'session': {'BACKEND': 'django.core.cache.backends.redis.RedisCache','LOCATION': 'redis://127.0.0.1:6379/2','TIMEOUT': 86400, # 1天}
}# 会话引擎配置
SESSION_ENGINE = 'django.contrib.sessions.backends.cache'
SESSION_CACHE_ALIAS = 'session'
三、视图缓存实现
3.1 视图装饰器缓存
# views.py
from django.views.decorators.cache import cache_page
from django.views.decorators.vary import vary_on_cookie, vary_on_headers
from django.core.cache import cache
from django.shortcuts import render
from .models import Article# 简单的视图缓存
@cache_page(60 * 15) # 缓存15分钟
def article_list(request):articles = Article.objects.all()return render(request, 'blog/article_list.html', {'articles': articles})# 基于cookie的缓存
@cache_page(60 * 15)
@vary_on_cookie
def user_articles(request):articles = Article.objects.filter(author=request.user)return render(request, 'blog/user_articles.html', {'articles': articles})# 基于请求头的缓存
@cache_page(60 * 15)
@vary_on_headers('User-Agent')
def responsive_view(request):# 根据User-Agent返回不同的模板user_agent = request.META.get('HTTP_USER_AGENT', '')template = 'mobile.html' if 'Mobile' in user_agent else 'desktop.html'return render(request, template)
3.2 高级视图缓存
from django.core.cache import cache
from django.conf import settings
from django.utils.cache import get_cache_key
from functools import wraps
import hashlibdef smart_cache_page(timeout=None, cache_key_prefix=None):def decorator(view_func):@wraps(view_func)def wrapper(request, *args, **kwargs):# 生成缓存键cache_key = generate_cache_key(request, view_func, args, kwargs)# 尝试从缓存获取响应response = cache.get(cache_key)if response is not None:return response# 执行视图函数response = view_func(request, *args, **kwargs)# 只缓存成功的响应if response.status_code == 200:cache.set(cache_key, response, timeout)return responsereturn wrapperreturn decoratordef generate_cache_key(request, view_func, args, kwargs):# 基础键key_parts = [view_func.__name__,request.path,request.GET.urlencode(),]# 如果是认证用户，添加用户IDif request.user.is_authenticated:key_parts.append(str(request.user.id))# 生成hashkey = hashlib.md5(''.join(key_parts).encode()).hexdigest()return f'view_cache_{key}'# 使用示例
@smart_cache_page(timeout=300) # 5分钟缓存
def article_detail(request, article_id):article = Article.objects.get(id=article_id)return render(request, 'blog/article_detail.html', {'article': article})
3.3 基于会话的缓存管理器
# cache_managers.py
from django.core.cache import caches
from django.conf import settings
import jsonclass SessionCacheManager:def __init__(self, session_key):self.session_key = session_keyself.cache = caches['session']def _get_user_cache_key(self, key):"""生成用户特定的缓存键"""return f'session_{self.session_key}_{key}'def get(self, key, default=None):"""获取缓存数据"""cache_key = self._get_user_cache_key(key)value = self.cache.get(cache_key)return json.loads(value) if value else defaultdef set(self, key, value, timeout=None):"""设置缓存数据"""cache_key = self._get_user_cache_key(key)self.cache.set(cache_key, json.dumps(value), timeout)def delete(self, key):"""删除缓存数据"""cache_key = self._get_user_cache_key(key)self.cache.delete(cache_key)def clear_all(self):"""清除该会话的所有缓存"""pattern = f'session_{self.session_key}_*'self.cache.delete_pattern(pattern)# 使用中间件自动处理会话缓存
class SessionCacheMiddleware:def __init__(self, get_response):self.get_response = get_responsedef __call__(self, request):# 为请求添加缓存管理器request.cache_manager = SessionCacheManager(request.session.session_key)response = self.get_response(request)return response
四、缓存流程图
五、实际应用示例
5.1 商品列表缓存
# views.py
from django.views.decorators.cache import cache_page
from django.core.cache import cache
from .models import Productclass ProductListView:def get_products(self, category=None, page=1):# 生成缓存键cache_key = f'products_list_{category}_{page}'products = cache.get(cache_key)if products is None:# 查询数据库queryset = Product.objects.all()if category:queryset = queryset.filter(category=category)# 分页paginator = Paginator(queryset, 20)products = paginator.get_page(page)# 缓存结果cache.set(cache_key, products, 300) # 5分钟缓存return products@cache_page(60 * 5)def list_view(self, request):category = request.GET.get('category')page = request.GET.get('page', 1)products = self.get_products(category, page)return render(request, 'shop/product_list.html', {'products': products})
5.2 用户购物车缓存
# cart.py
class CartManager:def __init__(self, request):self.session_key = request.session.session_keyself.cache = caches['session']def get_cart_key(self):return f'cart_{self.session_key}'def get_cart(self):return self.cache.get(self.get_cart_key()) or {}def add_item(self, product_id, quantity=1):cart = self.get_cart()product_id = str(product_id)if product_id in cart:cart[product_id]['quantity'] += quantityelse:cart[product_id] = {'quantity': quantity,'added_at': datetime.now().isoformat()}self.cache.set(self.get_cart_key(), cart, 86400) # 1天def remove_item(self, product_id):cart = self.get_cart()product_id = str(product_id)if product_id in cart:del cart[product_id]self.cache.set(self.get_cart_key(), cart)def clear(self):self.cache.delete(self.get_cart_key())
六、性能优化建议
-
缓存键设计
- 使用有意义的前缀
- 避免过长的键名
- 包含版本信息
-
缓存粒度控制
- 合理设置过期时间
- 避免过度缓存
- 考虑缓存成本
-
缓存更新策略
- 主动更新
- 被动失效
- 版本控制
-
缓存监控
- 命中率统计
- 内存使用监控
- 性能分析
七、测试用例
# tests.py
from django.test import TestCase, Client
from django.core.cache import cache
from django.urls import reverseclass ViewCacheTests(TestCase):def setUp(self):self.client = Client()cache.clear()def test_cached_view(self):# 第一次请求response1 = self.client.get(reverse('article_list'))content1 = response1.content# 修改数据Article.objects.create(title='Test Article')# 第二次请求应该返回缓存的内容response2 = self.client.get(reverse('article_list'))content2 = response2.contentself.assertEqual(content1, content2)
八、常见问题和解决方案
- 缓存穿透
def get_data(self, key):# 使用空值标记value = cache.get(key)if value is None:data = expensive_operation()if data is None:# 缓存空值，避免频繁查询cache.set(key, 'NULL', 300)else:cache.set(key, data)return datareturn None if value == 'NULL' else value
- 缓存雪崩
import randomdef set_with_jitter(key, value, timeout):"""添加随机过期时间，避免同时失效"""jitter = random.randint(-60, 60)final_timeout = timeout + jittercache.set(key, value, final_timeout)
- 缓存一致性
def update_data(self, key, value):"""先更新数据库，再删除缓存"""try:# 更新数据库self.model.objects.filter(pk=key).update(value=value)# 删除缓存cache.delete(f'data_{key}')except Exception as e:# 记录错误，可能需要后续处理logger.error(f'Failed to update data: {e}')
九、总结
通过本章学习，你应该掌握：
- Django视图缓存的基本使用
- 会话缓存的实现方法
- 缓存性能优化策略
- 常见缓存问题的解决方案
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