Simple Djano cache system for function/class-based views with automatic key generation

django_cache_for_views.py

#!/usr/bin/env python
# coding: utf-8

from asset.models import *
from common.models import *
from cost.models import *
from django.core.cache import cache
import inspect
from django.contrib.contenttypes.models import ContentType
from django.db.models.signals import pre_save, pre_delete


KeyRegistry = "KeyRegistry"


def generate_key(seperator, *args):
    """
    :param seperator: key中的分隔符, 比如'-', '.'
    :param args: 需要添加到key中的参数
    :return: 生成的key
    这个函数用来生成缓存的key, 有两种模式
    1. class based view
        会读取class name和method name
    2. function view
        会读取function name
    最后用传入的seperator把所有东西, 包括args连接起来, 作为key返回
    """
    key = []
    frame_back = inspect.currentframe().f_back
    func_name = frame_back.f_code.co_name

    key.append(func_name)
    if 'self' in frame_back.f_locals:
        class_name = frame_back.f_locals['self'].__class__.__name__
        key.insert(0, class_name)

    key = seperator.join(key + [str(arg) for arg in args])
    return key


def get_cachevalue(key):
    """
    :param key: 缓存key值
    :return: cached value
    从缓存中获取结果, 结果可能为空
    """
    cached_value = cache.get(key)
    return cached_value


def set_cachevalue(key, value, models):
    """
    :param key: 缓存key值
    :param value: 和key对应的value值
    :param models: model列表, 字符串类型, e.g. ["Switch", "Server"]
    :return:
    """
    if (isinstance(models, list) and all(isinstance(m, str) for m in models)):
        try:
            for modelname in models:
                model_cls = ContentType.objects.get(model=modelname).model_class()
                if KeyRegistry in dir(model_cls):
                    model_cls.KeyRegistry.append(key)
                else:
                    model_cls.KeyRegistry = [key]
        except KeyError:
            print("必须使用Model定义时的名字")
        cache.set(key, value)
    else:
        print("models必须是字符串构成的列表!")


def _clear_cache_when_save(sender, **kwargs):
    '''
    逻辑是, 只要某个Model的数据发生改变, 那么缓存中相关联的所有key-value都删除
    因为没有办法在Model中知晓views中的逻辑, 无法【更新】缓存, 只能删除
    '''
    if KeyRegistry not in sender.__dict__:
        pass
    else:
        for key in sender.__dict__[KeyRegistry]:
            cache.delete(key)


def _clear_cache_when_delete(sender, **kwargs):
    if KeyRegistry not in sender.__dict__:
        pass
    else:
        for key in sender.__dict__[KeyRegistry]:
            cache.delete(key)


pre_save.connect(_clear_cache_when_save)
pre_delete.connect(_clear_cache_when_delete)

How to use it, an example (which is using djangorestframwork but you get the idea):

@api_view(['GET'])
def cost_month_detail(request):
    """  
    获取某个成本某月的详细采购记录
    """
    costs = Cost.objects.all()
    item = request.QUERY_PARAMS.get('item', 'undefined')
    cost_type = COST_TYPE_KEY_MAP.get(item, COST_TYPE_UNDEFINED)
    month = request.QUERY_PARAMS.get('month', None)
    key = generate_key('.' , *[item, month])
    data = get_cachevalue(key)
    if not data:
        req_ym_str = month.split('.')
        req_ym_int = [int(req_ym_str[0]), int(req_ym_str[1])]

        if cost_type and req_ym_int:
            costs = costs.filter( cost_type=cost_type,\
                    purchase_date__year=req_ym_int[0],\
                    purchase_date__month=req_ym_int[1])
        serializer = CostSerializer(costs)
        data = serializer.data
        set_cachevalue(key, data, [models[item]])
    return Response(data)