# Multi 命令用于標(biāo)記一個(gè)事務(wù)塊的開(kāi)始事務(wù)塊內(nèi)的多條命令會(huì)按照先后順序被放進(jìn)一個(gè)隊(duì)列當(dāng)中，最后由 EXEC 命令原子性( atomic )地執(zhí)行
> multi（開(kāi)始一個(gè)redis事物）
incr books
incr books
> exec （執(zhí)行事物）
> discard （丟棄事物）

> setnx lock:codehole true
.... do something critical ....
> del lock:codehole

> setnx lock:codehole true
> expire lock:codehole 5
.... do something critical ....
> del lock:codehole

> set lock:codehole true ex 5 nx
''' do something '''
> del lock:codehole

#! /usr/bin/env python
# -*- coding: utf-8 -*-
import redis
def sale(rs):
  while True:
    with rs.pipeline() as p:
      try:
        p.watch('apple')          # 監(jiān)聽(tīng)key值為apple的數(shù)據(jù)數(shù)量改變
        count = int(rs.get('apple'))
        print('拿取到了蘋果的數(shù)量: %d' % count)
        p.multi()             # 事務(wù)開(kāi)始
        if count> 0 :           # 如果此時(shí)還有庫(kù)存
          p.set('apple', count - 1)
          p.execute()          # 執(zhí)行事務(wù)
        p.unwatch()
        break               # 當(dāng)庫(kù)存成功減一或沒(méi)有庫(kù)存時(shí)跳出執(zhí)行循環(huán)
      except Exception as e:         # 當(dāng)出現(xiàn)watch監(jiān)聽(tīng)值出現(xiàn)修改時(shí)，WatchError異常拋出
        print('[Error]: %s' % e)
        continue              # 繼續(xù)嘗試執(zhí)行

rs = redis.Redis(host='127.0.0.1', port=6379)   # 連接redis
rs.set('apple',1000)                # # 首先在redis中設(shè)置某商品apple 對(duì)應(yīng)數(shù)量value值為1000
sale(rs)

import redis
import uuid
import time

# 1.初始化連接函數(shù)
def get_conn(host="127.0.0.1",port=6379):
  rs = redis.Redis(host=host, port=port)
  return rs

# 2. 構(gòu)建redis鎖
def acquire_lock(rs, lock_name, expire_time=10):
  '''
  rs: 連接對(duì)象
  lock_name: 鎖標(biāo)識(shí)
  acquire_time: 過(guò)期超時(shí)時(shí)間
  return -> False 獲鎖失敗 or True 獲鎖成功
  '''
  identifier = str(uuid.uuid4())
  end = time.time() + expire_time
  while time.time() < end:
    # 當(dāng)獲取鎖的行為超過(guò)有效時(shí)間，則退出循環(huán)，本次取鎖失敗，返回False
    if rs.setnx(lock_name, identifier): # 嘗試取得鎖
      return identifier
    # time.sleep(.001)
    return False

# 3. 釋放鎖
def release_lock(rs, lockname, identifier):
  '''
  rs: 連接對(duì)象
  lockname: 鎖標(biāo)識(shí)
  identifier: 鎖的value值，用來(lái)校驗(yàn)
  '''


  if rs.get(lockname).decode() == identifier: # 防止其他進(jìn)程同名鎖被誤刪
    rs.delete(lockname)
    return True      # 刪除鎖
  else:
    return False      # 刪除失敗

#有過(guò)期時(shí)間的鎖
def acquire_expire_lock(rs, lock_name, expire_time=10, locked_time=10):
  '''
  rs: 連接對(duì)象
  lock_name: 鎖標(biāo)識(shí)
  acquire_time: 過(guò)期超時(shí)時(shí)間
  locked_time: 鎖的有效時(shí)間
  return -> False 獲鎖失敗 or True 獲鎖成功
  '''
  identifier = str(uuid.uuid4())
  end = time.time() + expire_time
  while time.time() < end:
    # 當(dāng)獲取鎖的行為超過(guò)有效時(shí)間，則退出循環(huán)，本次取鎖失敗，返回False
    if rs.setnx(lock_name, identifier): # 嘗試取得鎖
      # print('鎖已設(shè)置: %s' % identifier)
      rs.expire(lock_name, locked_time)
      return identifier
    time.sleep(.001)
  return False


'''在業(yè)務(wù)函數(shù)中使用上面的鎖'''
def sale(rs):
  start = time.time()      # 程序啟動(dòng)時(shí)間
  with rs.pipeline() as p:
    '''
    通過(guò)管道方式進(jìn)行連接
    多條命令執(zhí)行結(jié)束，一次性獲取結(jié)果
    '''

    while 1:
      lock = acquire_lock(rs, 'lock')
      if not lock: # 持鎖失敗
        continue

      #開(kāi)始監(jiān)測(cè)"lock"
      p.watch("lock")
      try:
        #開(kāi)啟事務(wù)
        p.multi()
        count = int(rs.get('apple')) # 取量
        p.set('apple', count-1)   # 減量
        # time.sleep(5)
        
        #提交事務(wù)
        p.execute()
        print('當(dāng)前庫(kù)存量: %s' % count)
        #成功則跳出循環(huán)
        break
      except:
        #事務(wù)失敗對(duì)應(yīng)處理
        print("修改數(shù)據(jù)失敗")

      #無(wú)論成功與否最終都需要釋放鎖
      finally:

        res = release_lock(rs, 'lock', lock)
        #釋放鎖成功，
        if res:
          print("刪除鎖成功")
        #釋放鎖失敗，強(qiáng)制刪除
        else:
          print("刪除鎖失敗,強(qiáng)制刪除鎖")
          res = rs.delete('lock')
          print(res)

    print('[time]: %.2f' % (time.time() - start))

rs = redis.Redis(host='127.0.0.1', port=6379)   # 連接redis
# rs.set('apple',1000)               # # 首先在redis中設(shè)置某商品apple 對(duì)應(yīng)數(shù)量value值為1000
sale(rs)

def acquire_expire_lock(rs, lock_name, expire_time=10, locked_time=10):
  '''
  rs: 連接對(duì)象
  lock_name: 鎖標(biāo)識(shí)
  acquire_time: 過(guò)期超時(shí)時(shí)間
  locked_time: 鎖的有效時(shí)間
  return -> False 獲鎖失敗 or True 獲鎖成功
  '''
  identifier = str(uuid.uuid4())
  end = time.time() + expire_time
  while time.time() < end:
    # 當(dāng)獲取鎖的行為超過(guò)有效時(shí)間，則退出循環(huán)，本次取鎖失敗，返回False
    if rs.setnx(lock_name, identifier): # 嘗試取得鎖
      # print('鎖已設(shè)置: %s' % identifier)
      rs.expire(lock_name, locked_time)
      return identifier
    time.sleep(.001)
  return False