在一些實際環境中,如何實現主從的快速切換,在沒有MHA等工具的輔助下,如何避免影響線上的業務,一般都會在在業務低峯期進行主從切換,本腳本主要利用MySQL自帶的命令行工具(FLUSH TABLES WITH READ LOCK)進行鎖全庫,且由用戶自行輸入判斷多少秒內從庫BINLOG數據不在同步後,認爲主從數據已達一致性可以進行主從切換(在一些資料上說也可以用READ-ONLY來鎖庫,但需要注意如果寫入用戶具有Admin權限是不受限制),主從切換完成5秒後進行檢查主從是否同步問題.
##連接數據庫使用TCP/IP方式,需要相應的操作數據庫權限。
##目前判斷使用show master status 來判斷,可以show slave status返回的值來判斷,自行修改。
腳本:
#!/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]) ##從庫的遊標 time.sleep(1) slave_pos.append(self.execIo(cur1, "show master status")[1]) data.append(self.execIo(cur,"show master status")[1])##從庫的遊標 print ".......",data,slave_pos if data[0]==data[1] and slave_pos[0]==slave_pos[1]: try: print "第%s次判斷數據已經同步....."%n if n==c_time: print "開始主從切換工作........" self.exeStop(cur1,"stop slave") ##停止從庫同步 new_pos=self.exeStop(cur1,"show master status")#獲取新主庫的FILE和POS的值,遊標爲還沒切換前的從庫 #print "獲取新主庫的FILE和POS的值,遊標爲還沒切換前的從庫",new_pos self.exeStop(cur,"reset master;")##主庫釋放從庫主從信息...... ##在從庫執行new_change 指向新的主庫 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)##在原來主庫上執行change master to..... #print "在原來主庫上執行change master to...." self.exeStop(cur,"start slave") ##在原來主庫上執行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 "主從切換成功!" print "\n" while True: print "等待其他操作完成,即將unlock tables主庫......" try: stop = raw_input("輸入終止命令q即完成此次操作:\n") 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 "主從數據未達到一致性..........",n n=0 data=[] if __name__ =="__main__": c_time=int(raw_input("多少秒後進行主從切換..>>")) print "****************************************************\n" print "請根據提示輸入指定信息:" m_host = raw_input("目前主庫的地址:") m_user = raw_input("目前主庫的登陸用戶名:") m_password = raw_input("目前主庫的密碼:") m_port = int(raw_input("目前主庫的端口:")) print "****************************************************\n" s_host = raw_input("目前從庫的地址:") s_user = raw_input("目前從庫的登陸用戶名:") s_password = raw_input("目前從庫的密碼:") s_port = int(raw_input("目前從庫的端口:")) 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() ##獲取主庫遊標 cur1 = S.getConn() ##獲取從庫遊標 print "*****************************************************\n" print "主從同步用戶信息.........\n" s_user1 = raw_input("輸入主從同步的用戶>>:") s_password1 = raw_input("輸入主從同步的密碼:") s_port1 = int(raw_input("輸入主從同步的端口:")) M.execSQLstatus(cur,s_host,s_user1,s_password1,s_port1)