本篇文章小编给大家分享一下mysql服务器在无操作超时主动断开连接情况解决方法,文章代码介绍的很详细,小编觉得挺不错的,现在分享给大家供大家参考,有需要的小伙伴们可以来看看。
我们在使用mysql服务的时候,正常情况下,mysql的设置的timeout是8个小时(28800秒),也就是说,如果一个连接8个小时都没有操作,那么mysql会主动的断开连接,当这个连接再次尝试查询的时候就会报个”MySQL server has gone away”的误,但是有时候,由于mysql服务器那边做了一些设置,很多情况下会缩短这个连接timeout时长以保证更多的连接可用。有时候设置得比较变态,很短,30秒,这样就需要客户端这边做一些操作来保证不要让mysql主动来断开。
查看mysql的timeout
使用客户端工具或者Mysql命令行工具输入show global variables like '%timeout%';就会显示与timeout相关的属性,这里我用docker模拟了一个测试环境。
mysql> show variables like '%timeout%'; +-----------------------------+----------+ | Variable_name | Value | +-----------------------------+----------+ | connect_timeout | 10 | | delayed_insert_timeout | 300 | | have_statement_timeout | YES | | innodb_flush_log_at_timeout | 1 | | innodb_lock_wait_timeout | 50 | | innodb_rollback_on_timeout | OFF | | interactive_timeout | 30 | | lock_wait_timeout | 31536000 | | net_read_timeout | 30 | | net_write_timeout | 60 | | rpl_stop_slave_timeout | 31536000 | | slave_net_timeout | 60 | | wait_timeout | 30 | +-----------------------------+----------+ 13 rows in set
wait_timeout:服务器关闭非交互连接之前等待活动的秒数,就是你在你的项目中进行程序调用
interactive_timeout: 服务器关闭交互式连接前等待活动的秒数,就是你在你的本机上打开mysql的客户端,cmd的那种
使用pymysql进行查询
在数据库里随便创建了一个表,插入两条数据
mysql> select * from person; +----+------+-----+ | id | name | age | +----+------+-----+ | 1 | yang | 18 | | 2 | fan | 16 | +----+------+-----+ 2 rows in set
使用pymysql这个库对其进行查询操作,很简单
#coding:utf-8 import pymysql def mytest(): connection = pymysql.connect( host='localhost', port=3306, user='root', password='123456', db='mytest', charset='utf8') cursor = connection.cursor() cursor.execute("select * from person") data = cursor.fetchall() cursor.close() for i in data: print(i) cursor.close() connection.close() if __name__ == '__main__': mytest()
可以正确的得到结果
(1, 'yang', 18)
(2, 'fan', 16)
连接超时以后的查询
上面可以正常得到结果是由于当创建好一个链接以后,就立刻进行了查询,此时还没有超过它的超时时间,如果sleep一段时间,看看什么效果。
#coding:utf-8 import pymysql import time def mytest(): connection = pymysql.connect( host='localhost', port=3306, user='root', password='123456', db='mytest', charset='utf8') cursor = connection.cursor() cursor.execute("select * from person") data = cursor.fetchall() for i in data: print(i) cursor.close() time.sleep(31) cursor = connection.cursor() cursor.execute("select * from person") data2 = cursor.fetchall() for i in data2: print(i) cursor.close() connection.close() if __name__ == '__main__': mytest()
这里进行了两次查询,因为把mysql的wait_timeout设置了30秒,所以在第一次查询之后停了31秒,目的让mysql服务主动的和刚才创建的连接断开,得到的结果是
(1, 'yang', 18) (2, 'fan', 16) Traceback (most recent call last): File "F:/python/python3Test/mysqltest.py", line 29, inmytest() File "F:/python/python3Test/mysqltest.py", line 22, in mytest cursor.execute("select * from person") ... ... File "C:Python35libsite-packagespymysqlconnections.py", line 702, in _read_bytes CR.CR_SERVER_LOST, "Lost connection to MySQL server during query") pymysql.err.OperationalError: (2013, 'Lost connection to MySQL server during query') Process finished with exit code 1
可以看到在停了31秒钟以后,再次使用该连接进行查询将抛出2013, 'Lost connection to MySQL server during query'错误。
解决办法
解决的方法有两种,既然这里的超时是由于在规定时间内没有任何操作导致mysql主动的将链接关闭,pymysql的connection对象有一个ping()方法,可以检查连接是否有效,在每次执行查询操作之前先执行一下ping()方法,该方法默认的有个reconnect参数,默认是True,如果失去连接了会重连。
#coding:utf-8 import pymysql import time def mytest(): connection = pymysql.connect( host='localhost', port=3306, user='root', password='123456', db='mytest', charset='utf8') connection.ping() cursor = connection.cursor() cursor.execute("select * from person") data = cursor.fetchall() for i in data: print(i) cursor.close() time.sleep(31) connection.ping() cursor = connection.cursor() cursor.execute("select * from person") data2 = cursor.fetchall() for i in data2: print(i) cursor.close() connection.close() if __name__ == '__main__': mytest()
曾尝试使用另外一个线程不停来执行ping()操作,但是当这样做以后连接就会丢失,之后的操作就不能进行了。
#coding:utf-8 import pymysql import time import threading import traceback def ping(conn): while True: try: conn.ping() except: print(traceback.format_exc()) finally: time.sleep(1) def mytest(): connection = pymysql.connect( host='localhost', port=3306, user='root', password='123456', db='mytest', charset='utf8') cursor = connection.cursor() # 放在此处不行,必须等待cursor的一个execute之后再运行才可以 # th = threading.Thread(target=ping, args=(connection,)) # th.setDaemon(True) # th.start() cursor.execute("select * from person") data = cursor.fetchall() for i in data: print(i) cursor.close() # 线程放在此处启动可以 th = threading.Thread(target=ping, args=(connection,)) th.setDaemon(True) th.start() time.sleep(31) cursor = connection.cursor() cursor.execute("select * from person") data2 = cursor.fetchall() for i in data2: print(i) cursor.close() connection.close() if __name__ == '__main__': mytest()
还有一种方法是使用连接池,连接池中保持着指定数量的可用连接,每次重新获取一个有效的连接进行查询操作,pymysql本身不具有连接池功能,需要借住DBUtils
#coding:utf-8 import pymysql import time from DBUtils.PooledDB import PooledDB, SharedDBConnection def mytest(): pool = PooledDB( creator=pymysql, # 初始化时,连接池至少创建的空闲连接,0表示不创建 maxconnections=3, # 连接池中空闲的最多连接数,0和None表示没有限制 mincached=2, # 连接池中最多共享的连接数量,0和None表示全部共享(其实没什么卵用) maxcached=5, maxshared=3, host='localhost', port=3306, user='root', password='123456', db='mytest', charset='utf8' ) connection = pool.connection() cursor = connection.cursor() cursor.execute("select * from person") data = cursor.fetchall() for i in data: print(i) time.sleep(40) cursor.execute("select * from person") data2 = cursor.fetchall() for i in data2: print(i) cursor.close() connection.close() if __name__ == '__main__': mytest()
这种方式虽然可以正确的获取结果,但是实际的项目中并不会这么使用,而是在执行完查询语句以后要将connection关闭,注意这里的关闭并不是真正的关闭,而只是将连接返回给连接池让其它人使用.
#coding:utf-8 import pymysql import time from DBUtils.PooledDB import PooledDB, SharedDBConnection def mytest(): pool = PooledDB( creator=pymysql, maxconnections=3, # 初始化时,连接池至少创建的空闲连接,0表示不创建 mincached=2, # 连接池中空闲的最多连接数,0和None表示没有限制 maxcached=5, # 连接池中最多共享的连接数量,0和None表示全部共享(其实没什么卵用) maxshared=3, host='localhost', port=3306, user='root', password='123456', db='mytest', charset='utf8' ) connection = pool.connection() cursor = connection.cursor() cursor.execute("select * from person") data = cursor.fetchall() for i in data: print(i) cursor.close() # 关闭连接,其实并没有真正关闭,只是将连接返回给连接池 connection.close() time.sleep(40) connection = pool.connection() cursor = connection.cursor() cursor.execute("select * from person") data2 = cursor.fetchall() for i in data2: print(i) cursor.close() connection.close() if __name__ == '__main__': mytest()