# -*- coding: utf-8 -*-
# @Time    : 2019/9/30 22:03
# @Author  : CRJ
# @File    : utils.py
# @Software: PyCharm
# @Python3.6
import math
import time
import uuid

import redis


# 获取锁（乐观锁）
def acquire_lock_with_timeout(conn, lockname, acquire_timeout=5, lock_timeout=10):
    # 128位随机标识符
    identifier = str(uuid.uuid4())
    lockname = 'lock:' + lockname
    lock_timeout = int(math.ceil(lock_timeout))  # 确保传给exprie是整数

    end = time.time() + acquire_timeout
    while time.time() < end:
        if conn.setnx(lockname, identifier):
            conn.expire(lockname, lock_timeout)
            return identifier
        elif not conn.ttl(lockname):  # 为没有设置超时时间的锁设置超时时间
            conn.expire(lockname, lock_timeout)

        time.sleep(0.001)
    return False


# 释放锁（乐观锁）
def release_lock(conn, lockname, identifier):
    lockname = 'lock:' + lockname
    with conn.pipeline(True) as pipe:
        while True:
            try:
                pipe.watch(lockname)
                value = pipe.get(lockname)
                # 判断标志是否相同
                if value is not None and value == identifier:
                    pipe.multi()
                    pipe.delete(lockname)
                    pipe.execute()
                    return True

                # 不同则直接退出 return False
                pipe.unwatch()
                break
            except redis.exceptions.WatchError:
                pass

        return False