纠结的SqlAlchemy: SQLError: (OperationalError) (2006, ‘MySQL server has gone away’)

孤独750

　　纠结的SqlAlchemy: SQLError: (OperationalError) (2006, ‘MySQL server has gone away’)问题处理！
　　
　　发现问题，应用启动后，第二天来访问就出现该问题。
　　
　　在网上go了一下，发现是mysql长连接超时。
　　
　　1. 查Mysql超时情况。
　　show variables like '%timeout%'
　　
　　wait_timeout = 28800
　　
　　mysql默认等待超时是8个小时
　　
　　过了1晚上肯定有问题。
　　
　　2. 查看sqlalchemy链接问题
　　
　　create_engine(url,pool_size=20, max_overflow=-1, pool_recycle=true,echo=True) 
　　
　　查了源码：
　　
　　:param pool_recycle=-1: this setting causes the pool to recycle
　　connections after the given number of seconds has passed. It
　　defaults to -1, or no timeout. For example, setting to 3600
　　means connections will be recycled after one hour. Note that
　　MySQL in particular will disconnect automatically if no
　　activity is detected on a connection for eight hours (although
　　this is configurable with the MySQLDB connection itself and the
　　server configuration as well).
　　
　　
　　pool_recycle is an integer number of seconds which to wait before 
　　   reopening a conneciton.  However, setting it to "True" is equivalent to 
          1 which means it will reopen connections constantly. 
　　
　　pool_recycle=true标识1秒重新链接一下
　　
　　3. 修改后pool_recycle=7200
　　2小时链接一次
　　
　　
　　参考地址：
　　http://groups.google.com/group/sqlalchemy/browse_thread/thread/9412808e695168ea/c31f5c967c135be0?pli=1
　　http://dba007.blog.iyunv.com/2876338/788315
　　http://hi.baidu.com/limodou/item/2d00f3333cc3b884c3cf29f7