主要是滲透了解 asyncio  相關概念

提及部分描述：1.執行緒（阻塞，非阻塞）

　　　　　　　2.執行緒之間通訊（執行緒之間的傳遞（import queue））

　　   　　　　 3.程序之間通訊（程序之間通訊from multiprocessing import Process,Queue  用程序Queue）單獨詳解）

舉例圖：

場景描述：

資料庫的要操作的表的資訊為：

     當多個請求都到資料庫操作介面程式的時候，針對同一個name的count進行增加或者減少，就要保證操作的同一個時刻只有一個可以去獲取count的值並進行update操作，所以我是在這一步增加了鎖，因為使用aiohttp寫的，所以想要在這裡也用了aiorwlock，但是在我測試的過程中發現了，當一個協程獲取鎖還沒釋放鎖的時候，另外一個協程也獲取到鎖，下面我是具體的程式碼

核心程式：

class CntHandler(object):

    def __init__(self, db, loop):
        self.db = db
        self.loop = loop
        self.company_lock = {}

    def response(self, request, msg):
        peer = request.transport.get_extra_info('peername')
        logging.info("request url[%s] from[%s]: %s
 
", request.raw_path, peer, msg)
        origin = request.headers.get("Origin")
        if origin is not None:
            headers = {"Access-Control-Allow-Origin": origin, "Access-Control-Allow-Credentials": "true"}
            resp = web.Response(text=util.dictToJson(msg), content_type='application/json
 
', headers=headers)
        else:
            resp = web.Response(text=util.dictToJson(msg), content_type='application/json')
        return resp

    async def cnt_set(self, request):
        """
        用於設定company表中的count值
        :param request: 
        :return: 
        """
        post = await request.post()
        logging.info('post %s', post)
        company_name = post.get("company")
        cnt = post.get("cnt")
        sql = "update shield.company set count=%s where name=%s"
        args_values = [cnt, company_name]
        rwlock = self.company_lock.get(company_name, "")
        if not rwlock:
            rwlock = aiorwlock.RWLock(loop=self.loop)
            self.company_lock[company_name] = rwlock
        async with rwlock.writer:
            msg = dict()
            po_sql = "select * from shield.company where name=%s"
            po = await self.db.get(po_sql, company_name)
            if not po:  # 找不到企業
                logging.error("not found company name [%s]", company_name)
                msg["code"] = 404
                msg["code"] = "not found company"
                return self.response(request, msg)
            res = await self.db.execute(sql, args_values)
            if not isinstance(res, int):
                logging.error("sql update is err:", res)
                msg["code"] = 403
                msg["reason"] = "set fail"
                return self.response(request, msg)
            logging.info("company [%s] set cnt [%s] is success", company_name, cnt)
            msg["code"] = 200
            msg["reason"] = "ok"
            return self.response(request, msg)

    async def cnt_inc(self, request):
        """
        用於增加company表中的count值
        :param request: 
        :return: 
        """
        post = await request.post()
        logging.info('post %s', post)
        company_name = post.get("company")
        cnt = int(post.get("cnt", 0))
        rwlock = self.company_lock.get(company_name, "")
        if not rwlock:
            rwlock = aiorwlock.RWLock(loop=self.loop)
            self.company_lock[company_name] = rwlock
        async with rwlock.writer:
            uuid_s = uuid.uuid1().hex
            logging.debug("[%s]---[%s]", uuid_s, id(rwlock))
            msg = dict()
            sql = "select * from shield.company where name=%s"
            po = await self.db.get(sql, company_name)
            if not po:  # 找不到企業
                logging.error("not found company name [%s]", company_name)
                msg["code"] = 404
                msg["code"] = "not found company"
                return self.response(request, msg)
            old_cnt = po.get("count")
            po_cnt = int(po.get("count"))
            res = po_cnt + cnt
            update_sql = "update shield.company set count=%s where name=%s"
            args_values = [res, company_name]
            update_res = await self.db.execute(update_sql, args_values)
            if not isinstance(update_res, int):  # 資料庫update失敗
                logging.error("sql update is err:", update_res)
                msg["code"] = 403
                msg["reason"] = "inc fail"
                return self.response(request, msg)
            logging.info("uuid [%s] lock [%s] company [%s] inc cnt [%s] old cnt [%s]  true will is [%s] success", uuid_s,id(rwlock), company_name, cnt, old_cnt, res)
            msg["code"] = 200
            msg["reason"] = "ok"
            return self.response(request, msg)

    async def cnt_dec(self, request):
        """
        用於減少company表中count的值
        :param request: 
        :return: 
        """
        post = await request.post()
        logging.info('post %s', post)
        company_name = post.get("company")
        cnt = int(post.get("cnt", 0))
        rwlock = self.company_lock.get(company_name, "")
        if not rwlock:
            rwlock = aiorwlock.RWLock(loop=self.loop)
            self.company_lock[company_name] = rwlock
        async with rwlock.writer:
            uuid_s = uuid.uuid1().hex
            logging.debug("[%s]---[%s]", uuid_s, id(rwlock))
            msg = dict()
            sql = "select * from shield.company where name=%s"
            po = await self.db.get(sql, company_name)
            if not po:      # 找不到企業
                logging.error("not found company name [%s]", company_name)
                msg["code"] = 404
                msg["code"] = "not found company"
                return self.response(request, msg)
            po_cnt = int(po.get("count"))
            old_cnt = po.get("count")
            if po_cnt == 0:
                logging.error("company [%s] cnt is 0", company_name)
                msg["code"] = 400
                msg["reason"] = "cnt is 0"
                return self.response(request, msg)
            if po_cnt < cnt:  # 資料庫餘額不足
                logging.error("company [%s] count is not enough", company_name)
                msg["code"] = 405
                msg["reason"] = "count is not enough"
                return self.response(request, msg)
            res = po_cnt - cnt
            update_sql = "update shield.company set count=%s where name=%s"
            args_values = [res, company_name]
            update_res = await self.db.execute(update_sql, args_values)
            if not isinstance(update_res, int): # 執行update 失敗
                logging.error("sql update is err:", update_res)
                msg["code"] = 403
                msg["reason"] = "inc fail"
                return self.response(request, msg)
            logging.info("uuid [%s] lock [%s] company [%s] dec cnt [%s] old cnt [%s] true will is [%s] success",uuid_s,id(rwlock), company_name, cnt, old_cnt, res)

            msg["code"] = 200
            msg["reason"] = "ok"
            return self.response(request, msg)

上面程式碼出問題的程式碼是在增加和減少的時候：

async with rwlock.writer:

在一個協程還沒有釋放鎖的時候，另外一個操作也就進來了，到之後在測試併發的時候，對同一個name的count進行操作導致最後的count值不符合的問題

這個完整的程式碼地址：https://github.com/pythonsite/test_aiorwlock