mysql4.0是老版本了，但是有些早期使用的企业依然在用，在创建主从时特别是线上服务器创建主从时，保证数据的一致性是个大问题：比如创建完从库同步时出现重复数据重复执行（虽然数据条数一致，但数据有可能会不一致）等。在mysql5.0以上版本中，此时备份主库只用在mysqldump时加上-F、master-data=2，single-transaction参数，从库同步时导入备份，在取备份文件开头的bin-log和pos位置进行同步即可，不会出现数据重复执行等问题，他能确保同步时的一致性。比较悲剧的是，本人所用的数据库还没有升级，是4.0的版本，经过测试，写了一个专一用于4.0主从同步时主库备份的脚本，原理就是模拟5.0以上的备份过程来做的。也可以用于5.0以上的版本，但是5.0以上的版本没有必要这么做。大家可以参考。
#!/usr/bin/env python
# -*- coding: utf-8 -*-
#last update:2012-10-25
import os,sys,time,MySQLdb
import subprocess,threading
class mysql_dump():
def __init__(self):
self.STAT_IP = "192.168.1.110"
self.logfile = "/data/script/db_back/mysql_dump.log"
self.user = "dump"
self.passwd = "123456"
self.distid = "2"
def log_w(self,text):
now = time.strftime("%Y-%m-%d %H:%M:%S")
tt = str(now) + "\t" + str(text) + "\n"
f = open(self.logfile,'a+')
f.write(tt)
f.close()
def dump(self,dumpname,now):
cmd = "/usr/local/mysql/bin/mysqldump -A -Q -e --add-drop-table --add-locks --extended-insert --quick --no-autocommit --single-transaction -u%s -p%s | bzip2 -2 > %s" % (self.user,self.passwd,dumpname)
print time.strftime("%Y-%m-%d %H:%M:%S")
text = "Start mysqldump,Please wait ..."
print text
self.log_w(text)
a = subprocess.Popen(cmd,shell=True)
while 1:
b = subprocess.Popen.poll(a)
if b == 0:
text = "Mysqldump complete"
print text
self.log_w(text)
break
elif b is None:
print 'Mysqldump running'
time.sleep(30)
else:
print a.pid,'term'
break
self.rsync(dumpname)
def rsync(self,dumpname):
cmd = "rsync -az %s %s::asktao_db/db_back/" % (dumpname,self.STAT_IP)
text = "Start rsync to server(%s) ,Please wait ..." % self.STAT_IP
print text
self.log_w(text)
a = subprocess.Popen(cmd,shell=True)
while 1:
b = subprocess.Popen.poll(a)
if b == 0:
text = "Rsync complete"
print text
self.log_w(text)
break
elif b is None:
print 'Rsync running'
time.sleep(30)
else:
print a.pid,'term'
break
def bin_log(self):
try:
conn = MySQLdb.connect(host = '127.0.0.1',user = 'repl_monitor',passwd = '123456',connect_timeout=5)
cursor = conn.cursor()
cursor.execute("show master status")
alldata = cursor.fetchall()
cursor.close()
conn.close()
file = alldata[0][0]
Position = alldata[0][1]
text = "show master status: %s %s" % (file,Position)
print text
self.log_w(text)
return file,Position
except MySQLdb.Error,e:
text = e.args
print text
self.log_w(text)
sys.exit()
def lock(self):
try:
conn = MySQLdb.connect(host = 'localhost',user = self.user,passwd = self.passwd,connect_timeout=5)
cursor = conn.cursor()
text = "flush tables with read lock"
print text
self.log_w(text)
cursor.execute("flush tables with read lock")
text = "flush logs"
print text
self.log_w(text)
cursor.execute("flush logs")
file,Position = self.bin_log()
now = time.strftime("%Y%m%d%H%M")
dumpname = "/data/script/db_back/wd_%s_%s_%s_%s.bz2" % (self.distid,now,file,Position)
d = threading.Thread(target=self.dump, args=(dumpname,now))
d.start()
while 1:
if os.path.isfile(dumpname) and os.path.getsize(dumpname) > 0:
text = "UNLOCK TABLES"
print text
self.log_w(text)
cursor.execute("UNLOCK TABLES")
cursor.close()
conn.close()
break
except MySQLdb.Error,e:
text = e.args
print text
self.log_w(text)
sys.exit()
def work(self):
t = threading.Thread(target=self.lock, args=())
t.start()
if __name__ == "__main__":
boss = mysql_dump()
boss.work()
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