TorMySQL 封装的 async with 语句抛出了 AssertionError 异常

说明

1. 我的数据库和表都是没有问题的，不会有数据库不存在或者表结构错误的情况
2. 我用的是tornado 4.4.2，Tornado的文档中说到 Tornado 4.3后就支持Python 3中的async/await 关键字了。

正文

我这两天了解了一下 Python3 中的 async/await 语句，然后照猫画虎，对 TorMySQL 封装了一个 async with语句的上下文管理器：

代码如下：

#!/usr/bin/env python3 # -*- coding: utf-8 -*- from tornado.ioloop import IOLoop import tormysql class get_cursor: def __init__(self, pool): """ get_cursor 上下文管理器 针对`async with`语句封装的上下文管理器 """ self.pool = pool async def __aenter__(self): self.tx = await self.pool.begin() return self.tx async def __aexit__(self, exc_type, exc, tb): if tb is None: self.tx.commit() else: self.tx.rollback() async def insert(): pool = tormysql.helpers.ConnectionPool( max_cOnnections= 20, #max open connections idle_secOnds= 7200, #conntion idle timeout time, 0 is not timeout wait_connection_timeout = 3, #wait connection timeout host = "127.0.0.1", user = "root", passwd = "TEST", db = "test", charset = "utf8" ) async with get_cursor(pool) as cursor: cursor.execute("INSERT INTO test(id) VALUES(1)") ioloop = IOLoop.instance() ioloop.run_sync(insert) 

我执行了上述代码以后，抛出了如下的错误：

 /home/yundongx/tutorial/async [async]$ python3 async.py ERROR:tornado.application:Future <tornado.concurrent.Future object at 0x7f1983708470> exception was never retrieved: Traceback (most recent call last): File "/home/yundongx/.virtualenvs/async/lib/python3.5/site-packages/tornado/gen.py", line 1021, in run yielded = self.gen.throw(*exc_info) File "/home/yundongx/.virtualenvs/async/lib/python3.5/site-packages/tormysql/helpers.py", line 44, in commit yield self._connection.commit() File "/home/yundongx/.virtualenvs/async/lib/python3.5/site-packages/tornado/gen.py", line 1015, in run value = future.result() File "/home/yundongx/.virtualenvs/async/lib/python3.5/site-packages/tornado/concurrent.py", line 237, in result raise_exc_info(self._exc_info) File "<string>", line 3, in raise_exc_info File "/home/yundongx/.virtualenvs/async/lib/python3.5/site-packages/tormysql/util.py", line 14, in finish result = fun(*args, **kwargs) File "/home/yundongx/.virtualenvs/async/lib/python3.5/site-packages/pymysql/connections.py", line 767, in commit self._read_ok_packet() File "/home/yundongx/.virtualenvs/async/lib/python3.5/site-packages/pymysql/connections.py", line 746, in _read_ok_packet pkt = self._read_packet() File "/home/yundongx/.virtualenvs/async/lib/python3.5/site-packages/pymysql/connections.py", line 961, in _read_packet packet_header = self._read_bytes(4) File "/home/yundongx/.virtualenvs/async/lib/python3.5/site-packages/tormysql/connections.py", line 308, in _read_bytes future = self._rfile.read_bytes(num_bytes) File "/home/yundongx/.virtualenvs/async/lib/python3.5/site-packages/tormysql/connections.py", line 97, in read assert self._read_future is None, "Already reading" AssertionError: Already reading Exception ignored in: <generator object execute at 0x7f19836e2e60> RuntimeError: generator ignored GeneratorExit WARNING:root:Transaction has not committed or rollbacked <tormysql.connections.Connection object at 0x7f19837080b8> {'user': b'root', 'port': 3306, 'host': '127.0.0.1', 'database': b'test'}. 

然后我去数据库中查询这个表，发现数据已经插入成功了。

请问一下这个异常是什么意思啊（ PyMySQL 显示说Already reading是什么意思啊）？