如何检查MySQL连接是否在Python中打开？

Question

我正在使用MySQLdb（http://mysql-python.sourceforge.net/）。看来connection.open和connection.sqlstate（）不适合我。下面是代码：

def open(self): 
    #TODO: check the connection's status 
    # self.__conn.open OR self.__conn.sqlstate() 
    try: 
     print "sqlstate:"+str(self.__conn.sqlstate()) 
     print "open?"+str(self.__conn.open) 
     return "00000" == self.__conn.sqlstate() 
    except Exception as e: 
     print "Exception while checking MYSQL Connection:"+str(e) 
     return False 

但是，当我跑了 “sudo的服务mysql的停止;睡眠60; sudo的服务mysql的开始;”做测试。输出如下。看起来，以后的一段输出重复了（我终于杀死了这个过程）。当服务器关闭时，connection.open为1，connection.sqlstate（）为00000.但是，当服务器启动时，connection.executemany（）仍会引发异常。有任何想法吗？谢谢。

... 
    2015-10-20 14:09:06 Exception while executing statement:(2006, 'MySQL server has gone away') 
    2015-10-20 14:09:06 sqlstate:00000 
    2015-10-20 14:09:06 open?1 
    2015-10-20 14:09:06 Reconnected to MYSQL. 
    2015-10-20 14:09:06 Exception while executing statement:(2006, 'MySQL server has gone away') 
    2015-10-20 14:09:06 sqlstate:00000 
    2015-10-20 14:09:06 open?1 
    2015-10-20 14:09:06 Reconnected to MYSQL. 
    2015-10-20 14:09:06 Exception while executing statement:(2006, 'MySQL server has gone away') 
    2015-10-20 14:09:06 sqlstate:00000 
    2015-10-20 14:09:06 open?1 
    2015-10-20 14:09:06 Reconnected to MYSQL. 
    2015-10-20 14:09:06 Exception while executing statement:(2006, 'MySQL server has gone away') 
    2015-10-20 14:09:06 sqlstate:00000 
    2015-10-20 14:09:06 open?1 
... 

UPDATE

我再次测试。输出如下。每次睡眠都是10秒。输出正常，但即使服务器关闭，connection.open也是1。但connection.sqlstate（）是正确的（HY000）。

2015-10-20 14:35:56 Exception while executing statement:(2006, 'MySQL server has gone away') 
2015-10-20 14:35:56 Exception while ping:(2003, "Can't connect to MySQL server on '10.1.1.25' (111)") 
2015-10-20 14:35:56 sqlstate:HY000 
2015-10-20 14:35:56 open?1 
2015-10-20 14:35:56 sleeping... 
2015-10-20 14:36:06 Exception while ping:(2003, "Can't connect to MySQL server on '10.1.1.25' (111)") 
2015-10-20 14:36:06 sqlstate:HY000 
2015-10-20 14:36:06 open?1 
2015-10-20 14:36:06 sleeping... 
2015-10-20 14:36:16 Exception while ping:(2003, "Can't connect to MySQL server on '10.1.1.25' (111)") 
2015-10-20 14:36:16 sqlstate:HY000 
2015-10-20 14:36:16 open?1 
2015-10-20 14:36:16 sleeping... 
2015-10-20 14:36:26 Exception while ping:(2003, "Can't connect to MySQL server on '10.1.1.25' (111)") 
2015-10-20 14:36:26 sqlstate:HY000 
2015-10-20 14:36:26 open?1 
2015-10-20 14:36:26 sleeping... 
2015-10-20 14:36:36 Exception while ping:(2003, "Can't connect to MySQL server on '10.1.1.25' (111)") 
2015-10-20 14:36:36 sqlstate:HY000 
2015-10-20 14:36:36 open?1 
2015-10-20 14:36:36 sleeping... 
2015-10-20 14:36:46 Exception while ping:(2003, "Can't connect to MySQL server on '10.1.1.25' (111)") 
2015-10-20 14:36:46 sqlstate:HY000 
2015-10-20 14:36:46 open?1 
2015-10-20 14:36:46 sleeping... 
2015-10-20 14:36:56 Exception while ping:(2003, "Can't connect to MySQL server on '10.1.1.25' (111)") 
2015-10-20 14:36:56 sqlstate:HY000 
2015-10-20 14:36:56 open?1 
2015-10-20 14:36:56 sleeping... 
2015-10-20 14:37:06 sqlstate:00000 
2015-10-20 14:37:06 open?1 
2015-10-20 14:37:06 Reconnected to MYSQL. 

Answer 1

尝试这个 -

import MySQLdb 

def main(): 
    # Connect to the MySQL database 
    db = MySQLdb.connect(host = 'z.cs.utexas.edu', user = 'userName', passwd = 'password', db = 'dbName') 

    # Check if connection was successful 
    if (db): 
    # Carry out normal procedure 
    print "Connection successful" 
    else: 
    # Terminate 
    print "Connection unsuccessful" 

Answer 2

我一直在寻找这种解决方案一段时间，我无法找到一个完美的解决方案。

似乎没有一个这样做的直接方式。如果您尝试执行查询，则只会发现连接已关闭。

我最终会做类似这样的回答了一句： How to check the connection alive in python?

Answer 3

你应该这样的代码： 在每前执行，平了MySQL服务器，例如

import MySQLdb as db 
    class DB(object): 
     def __init__(self): 
      try: 
       self.conn =mdb.connect(host='***',port=3306,user='',passwd='') 
      if (self.conn): 
       INFO_LOG("DB init success") 
      else: 
       INFO_LOG("DB init fail") 
      self.conn.autocommit(True) 
      self.conn.select_db(DB_NAME) 
      self.cursor = self.conn.cursor() 
     except Exception as e: 
      CRITICAL_LOG("DB init fail %s " % str(e)) 
    def insert(self,player_id,cmd): 
     try: 
      if self.conn is None: 
       self.__init__() 
      else: 
       self.conn.ping(True) 
      self.cursor.execute('INSERT INTO table values("%s",%s")' % 
      (player_id,cmd)) 
     except Exception as e: 
      import traceback 
      traceback.print_exc() 
      #error ocurs,rollback 
      self.conn.rollback()