get_lock(str,timeout);

得到一个锁，锁名为str，持续时间为timeout。可以使用release_lock()或连接断开(正常非正常)解锁

若加锁成功：返回1

操作超时未：返回0

发生错误：返回去NULL

release_lock(str)

解开被get_lock加锁的锁

若锁被解开：返回1

若该线程尚未被创建锁：返回0（此时锁还没有解开）

若命名的锁不存在：返回NULL

若该锁从未被get_lock()的调用获取，或锁已经被提前解开：则该锁不存在

is_free_lock(str);

检查名为str的锁是否可以使用（没有被封锁）

若该锁可以使用（没有人在用这个锁）：返回1

若锁正在被使用：返回0

出现错误：返回NULL

is_used_lock(str); //检查锁名为str的锁是否正在被使用（被封锁）

被封锁：返回使用该锁用户的客户端的连接标识符（connection ID）

否则：返回NULL

示例

#!/usr/bin/env python3# -*- coding:utf-8 -*-import logging, timeimport pymysqlclass MysqLock:    def __init__(self, db):        self.db = db    def _execute(self, sql):        cursor = self.db.cursor()        try:            ret = None            cursor.execute(sql)            if cursor.rowcount != 1:                logging.error("Multiple rows returned in mysql lock function.")                ret = None            else:                ret = cursor.fetchone()            cursor.close()            return ret        except Exception as ex:            logging.error("Execute sql \"%s\" failed! Exception: %s", sql, str(ex))            cursor.close()            return None    def get_lock(self, lockstr, timeout):        """        设置锁        """        sql = "SELECT GET_LOCK('%s', %s)" % (lockstr, timeout)        ret = self._execute(sql)        if ret[0] == 0:            logging.debug("Another client has previously locked '%s'.", lockstr)            return False        elif ret[0] == 1:            logging.debug("The lock '%s' was obtained successfully.", lockstr)            return True        else:            logging.error("Error occurred!")            return None    def release_lock(self, lockstr):        """        释放锁        """        sql = "SELECT RELEASE_LOCK('%s')" % lockstr        ret = self._execute(sql)        if ret[0] == 0:            # 线程尚未被创建锁            logging.debug("The lock '%s' the lock is not released(the lock was not established by this thread).",                          lockstr)            return False        elif ret[0] == 1:            # 锁被解开            logging.debug("The lock '%s' the lock was released.", lockstr)            return True        else:            # 锁不存在            logging.error("The lock '%s' did not exist.", lockstr)            return None        # Init loggingdef init_logging():    sh = logging.StreamHandler()    logger = logging.getLogger()    logger.setLevel(logging.DEBUG)    formatter = logging.Formatter('%(asctime)s -%(module)s:%(filename)s-L%(lineno)d-%(levelname)s: %(message)s')    sh.setFormatter(formatter)    logger.addHandler(sh)    logging.info("Current log level is : %s", logging.getLevelName(logger.getEffectiveLevel()))def main():    init_logging()    db = pymysql.connect(host='localhost', user='root', passwd='123456')    lock_name = 'queue'    lock = MysqLock(db)    ret = lock.get_lock(lock_name, 10)    if not ret:        logging.error("Can't get lock! exit!")        quit()    time.sleep(10)    logging.info("You can do some synchronization work across processes!")    # TODO    # 可以处理一些事情    lock.release_lock(lock_name)if __name__ == "__main__":    main()

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