利用flask上下文管理原理，实现线程之间的数据安全

Posted 2022-01-01 zjbacke

 

由于一般的程序基本上都是IO密集型，如果只是为了保证数据的安全而去开启进程，这必定是浪费资源的行为；为了保证数据的安全，借用flask的上下文的原理，如下代码实现

 

from threading import Thread
import time

try:
    from greenlet import getcurrent as get_ident  # 协程的唯一标识
except ImportError:
    try:
        from thread import get_ident
    except ImportError:
        from _thread import get_ident  # 线程的唯一标识


class Local(object):
    def __init__(self):
        # 这里一定要用object来调用，因为用self调用的就会触发__setattr__方法，__setattr__方法里
        # 又会用self去赋值就又会调用__setattr__方法，就变成递归，最后循环调用，最后报错

        # __setattr__添加/修改属性会触发它的执行
        # __delattr__删除属性的时候会触发
        # __getattr__只有在使用点调用属性且属性不存在的时候才会触发

        object.__setattr__(self, ‘__storage__‘, )
        object.__setattr__(self, ‘__ident_func__‘, get_ident)

        self.i = 0

    def __getattr__(self, name):
        try:
            return self.__storage__[self.__ident_func__()][name]
        except KeyError:
            raise AttributeError(name)

    def __setattr__(self, name, value):
        ident = self.__ident_func__()
        storage = self.__storage__
        try:
            storage[ident][name] = value
        except KeyError:
            storage[ident] = name: value

    def __delattr__(self, name):
        try:
            del self.__storage__[self.__ident_func__()][name]
        except KeyError:
            raise AttributeError(name)


local_values = Local()


def demo1_process():
    local_values.i = 1
    time.sleep(1)
    print(local_values.i)


def demo2_process():
    local_values.i = 2
    time.sleep(1)
    print(local_values.i)


def run():
    print("start:")
    t = Thread(target=demo1_process)
    t.start()
    t1 = Thread(target=demo2_process)
    t1.start()


run()