在一些实际环境中，如何实现主从的快速切换，在没有MHA等工具的辅助下，如何避免影响线上的业务，一般都会在在业务低峰期进行主从切换，本脚本主要利用MySQL自带的命令行工具(FLUSH TABLES WITH READ LOCK)进行锁全库，且由用户自行输入判断多少秒内从库BINLOG数据不在同步后，认为主从数据已达一致性可以进行主从切换(在一些资料上说也可以用READ-ONLY来锁库，但需要注意如果写入用户具有Admin权限是不受限制),主从切换完成5秒后进行检查主从是否同步问题.
连接数据库使用TCP/IP方式，需要相应的操作数据库权限。
目前判断使用show master status 来判断，可以show slave status返回的值来判断，自行修改。
yum install MySQL-python
脚本:switch_master_slave.py
#!/usr/bin/env python # -*- coding: utf-8 -*- import MySQLdb import time import sys class m_s: def __init__(self,host,user,password,port): self.host=host self.user=user self.passowrd=password self.port=port def getConn(self,db="mysql"): try: conn=MySQLdb.connect(host=self.host, user=self.user, passwd=self.passowrd, db=db, port=self.port, charset="utf8") cur = conn.cursor() return cur except Exception as e: return e def execSQLlock(self,*args): flush_sql="FLUSH TABLES WITH READ LOCK" cur.execute(flush_sql) def execIo(self,cur,command): cur.execute(command) db_pos = cur.fetchall() for value in db_pos: value=value return value def exeStop(self,cur,command): cur.execute(command) db_pos = cur.fetchall() return db_pos def execSQLstatus(self,*args): n=0 self.execSQLlock(cur) flush_m = "flush logs" cur.execute(flush_m) while True: data=[] slave_pos=[] n=n+1 exe_sql = "select Command,State,Info,Id from information_schema.processlist" cur.execute(exe_sql) plist = cur.fetchall() for li in range(len(plist)): if plist[li][0] == "Query" and plist[li][1] == "Waiting for global read lock": lock_id = "kill " + str(plist[li][3]) print plist[li][2] cur.execute(lock_id) slave_pos.append(self.execIo(cur1, "show master status")[1]) data.append(self.execIo(cur1,"show slave status")[6]) ##从库的游标 time.sleep(1) slave_pos.append(self.execIo(cur1, "show master status")[1]) data.append(self.execIo(cur,"show master status")[1])##从库的游标 print ".......",data,slave_pos if data[0]==data[1] and slave_pos[0]==slave_pos[1]: try: print "第%s次判断数据已经同步....."%n if n==c_time: print "开始主从切换工作........" self.exeStop(cur1,"stop slave") ##停止从库同步 new_pos=self.exeStop(cur1,"show master status")#获取新主库的FILE和POS的值,游标为还没切换前的从库 #print "获取新主库的FILE和POS的值,游标为还没切换前的从库",new_pos self.exeStop(cur,"reset master;")##主库释放从库主从信息...... ##在从库执行new_change 指向新的主库 self.exeStop(cur1,"reset slave all") new_change="change master to master_host='"+str(args[1])+"'"+",master_user='"+args[2]+"'"+",master_password='"+args[3]+"',master_port="+str(args[4])+",MASTER_LOG_FILE='"+str(new_pos[0][0])+"'"+",MASTER_LOG_POS="+str(new_pos[0][1]) print new_change self.exeStop(cur,new_change)##在原来主库上执行change master to..... #print "在原来主库上执行change master to...." self.exeStop(cur,"start slave") ##在原来主库上执行change master to..... time.sleep(5) s_pos=self.exeStop(cur,"show slave status;") #print s_pos[0][10],s_pos[0][11] if s_pos[0][10]=="Yes" and s_pos[0][11]=="Yes": self.exeStop(cur1,"reset slave all") print "主从切换成功!" print " " while True: print "等待其他操作完成,即将unlock tables主库......" try: stop = raw_input("输入终止命令q即完成此次操作: ") if stop == "q": sys.exit() # break except Exception as e: print "good bye" else: print s_pos[0][19] break except Exception as e: return e else: print "主从数据未达到一致性..........",n n=0 data=[] if __name__ =="__main__": c_time=int(raw_input("多少秒后进行主从切换..>>")) print "**************************************************** " print "请根据提示输入指定信息:" m_host = raw_input("目前主库的地址:") m_user = raw_input("目前主库的登陆用户名:") m_password = raw_input("目前主库的密码:") m_port = int(raw_input("目前主库的端口:")) print "**************************************************** " s_host = raw_input("目前从库的地址:") s_user = raw_input("目前从库的登陆用户名:") s_password = raw_input("目前从库的密码:") s_port = int(raw_input("目前从库的端口:")) M = m_s(m_host, m_user, m_password, m_port) S = m_s(s_host,s_user,s_password,s_port) cur = M.getConn() ##获取主库游标 cur1 = S.getConn() ##获取从库游标 print "***************************************************** " print "主从同步用户信息......... " s_user1 = raw_input("输入主从同步的用户>>:") s_password1 = raw_input("输入主从同步的密码:") s_port1 = int(raw_input("输入主从同步的端口:")) M.execSQLstatus(cur,s_host,s_user1,s_password1,s_port1)
# python switch_master_slave.py 多少秒后进行主从切换..>>5 **************************************************** 请根据提示输入指定信息: 目前主库的地址:192.168.56.100 目前主库的登陆用户名:wanbin 目前主库的密码:mysql 目前主库的端口:3306 **************************************************** 目前从库的地址:192.168.56.200 目前从库的登陆用户名:wanbin 目前从库的密码:mysql 目前从库的端口:3306 ***************************************************** 主从同步用户信息......... 输入主从同步的用户>>:repl 输入主从同步的密码:wanbin 输入主从同步的端口:3306 ....... [234L, 234L] [250L, 250L] 第1次判断数据已经同步..... ....... [234L, 234L] [250L, 250L] 第2次判断数据已经同步..... ....... [234L, 234L] [250L, 250L] 第3次判断数据已经同步..... ....... [234L, 234L] [250L, 250L] 第4次判断数据已经同步..... ....... [234L, 234L] [250L, 250L] 第5次判断数据已经同步..... 开始主从切换工作........ change master to master_host='192.168.56.200',master_user='repl',master_password='wanbin',master_port=3306,MASTER_LOG_FILE='my3306_binlog.000018',MASTER_LOG_POS=250 switch_master_slave.py:29: Warning: Sending passwords in plain text without SSL/TLS is extremely insecure. cur.execute(command) switch_master_slave.py:29: Warning: Storing MySQL user name or password information in the master info repository is not secure and is therefore not recommended. Please consider using the USER and PASSWORD connection options for START SLAVE; see the 'START SLAVE Syntax' in the MySQL Manual for more information. cur.execute(command) 主从切换成功! 等待其他操作完成,即将unlock tables主库...... 输入终止命令q即完成此次操作: 等待其他操作完成,即将unlock tables主库...... 输入终止命令q即完成此次操作: q 等待其他操作完成,即将unlock tables主库...... 输入终止命令q即完成此次操作: q