**************************前言*********************************************************一.主从的作用：1.可以当做一种备份方式2.用来实现读写分离，缓解一个数据库的压力二.环境
**************************前言*********************************************************
一.主从的作用：
1.可以当做一种备份方式
2.用来实现读写分离，缓解一个数据库的压力
二.环境：
OS CentOS5.5
DB MySQL5.5.3-m3
三.MySQL主从备份原理
master 上提供binlog ,
slave 通过 I/O线程从 master拿取 binlog,并复制到slave的中继日志中
slave 通过 SQL线程从 slave的中继日志中读取binlog ,然后解析到slave中
四.主从复制大前提
需要master与slave同步，因为笔者的数据库数据量不大，所以无需考虑太多，直接把
master上的data复制到了slave上，但是如果是大的数据量，比如像taobao这个的系统
那么数据同步也是很难得，需要有一个完善的方案，有兴趣的可以看看这篇文章
http://www.taobaodba.com/html/564_%E5%A2%9E%E9%87%8F%E6%97%A5%E5%BF%97%E8%BF%AD%E4%BB%A3%E5%90%8C%E6%AD%A5%E5%92%8C%E9%98%BF%E5%9F%BA%E9%87%8C%E6%96%AF%E6%82%96%E8%AE%BA.html
**************************开始***************************************************
一.将master设置为只读。
mysql> flush tables with read lock;
二.用master中的data文件夹替换slave中的data文件夹
比如 用 tar zcvf mysql_data.gz /media/raid10/mysql/3306/data
然后 mv mysql_data.gz /media/raid10/htdocs/blog/wordpress/
因为我的 /media/raid10/htdocs/blog/wordpress/ 是 Nginx 的主目录
所以可以在 slave上，用wget下载这个文件，然后 解压，并覆盖slave上的data文件
注意：覆盖之前最好备份源文件
三.配置master的my.cnf,添加以下内容
在[mysqld]配置段添加如下字段
server-id=1
log-bin=/media/raid10/mysql/3306/binlog/binlog //这里写你的binlog绝对路径名
binlog-do-db=blog //需要同步的数据库，如果没有本行，即表示同步所有的数据库
binlog-ignore-db=mysql //被忽略的数据库
这里给出我的my.cnf配置文件
[client]
character-set-server = utf8
port = 3306
socket = /tmp/mysql.sock
[mysqld]
character-set-server = utf8
replicate-ignore-db = mysql
replicate-ignore-db = test
replicate-ignore-db = information_schema
user = mysql
port = 3306
socket = /tmp/mysql.sock
basedir = /usr/local/webserver/mysql
datadir = /media/raid10/mysql/3306/data
log-error = /media/raid10/mysql/3306/mysql_error.log
pid-file = /media/raid10/mysql/3306/mysql.pid
open_files_limit = 10240
back_log = 600
max_connections = 5000
max_connect_errors = 6000
table_cache = 614
external-locking = FALSE
max_allowed_packet = 16M
sort_buffer_size = 1M
join_buffer_size = 1M
thread_cache_size = 300
#thread_concurrency = 8
query_cache_size = 20M
query_cache_limit = 2M
query_cache_min_res_unit = 2k
default-storage-engine = MyISAM
thread_stack = 192K
transaction_isolation = READ-COMMITTED
tmp_table_size = 20M
max_heap_table_size = 20M
long_query_time = 3
log-slave-updates
log-bin = /media/raid10/mysql/3306/binlog/binlog
binlog-do-db=blog
binlog-ignore-db=mysql
binlog_cache_size = 4M
binlog_format = MIXED
max_binlog_cache_size = 8M
max_binlog_size = 20M
relay-log-index = /media/raid10/mysql/3306/relaylog/relaylog
relay-log-info-file = /media/raid10/mysql/3306/relaylog/relaylog
relay-log = /media/raid10/mysql/3306/relaylog/relaylog
expire_logs_days = 30
key_buffer_size = 10M
read_buffer_size = 1M
read_rnd_buffer_size = 6M
bulk_insert_buffer_size = 4M
myisam_sort_buffer_size = 8M
myisam_max_sort_file_size = 20M
myisam_repair_threads = 1
myisam_recover
interactive_timeout = 120
wait_timeout = 120
skip-name-resolve
#master-connect-retry = 10
slave-skip-errors = 1032,1062,126,1114,1146,1048,1396
#master-host = 192.168.1.2
#master-user = username
#master-password = password
#master-port = 3306
server-id = 1
innodb_additional_mem_pool_size = 16M
innodb_buffer_pool_size = 20M
innodb_data_file_path = ibdata1:56M:autoextend
innodb_file_io_threads = 4
innodb_thread_concurrency = 8
innodb_flush_log_at_trx_commit = 2
innodb_log_buffer_size = 16M
innodb_log_file_size = 20M
innodb_log_files_in_group = 3
innodb_max_dirty_pages_pct = 90
innodb_lock_wait_timeout = 120
innodb_file_per_table = 0
#log-slow-queries = /media/raid10/mysql/3306/slow.log
#long_query_time = 10
[mysqldump]
quick
max_allowed_packet = 32M
四.在master机上为slave机添加一同步帐号
mysql> grant replication slave on *.* to 'admin'@'172.29.141.115' identified by '12345678';
mysql> flush privileges ;
五.配置slave的my.cnf,添加以下内容
注意:
1.如果mysql是5.5.3-m3 的版本，只需
在[mysqld]字段下添加如下内容
server-id=2
2.如果是5.0x的版本，需要
在[mysqld]字段下添加如下内容
server-id=2
log-bin=mysql-bin //这是同步的binlog，具体以你的binlog为准
master-host=172.29.141.112
master-user=admin
master-password=12345678
master-port=3306
master-connect-retry=60 //如果发现主服务器断线，重新连接的时间差；
replicate-do-db=blog //同步的数据库，不写本行 表示 同步所有数据库
replicate-ignore-db=mysql //不需要备份的数据库
log-slave-update
slave-skip-errors
我的mysql是5.5.3-m3，这里给出我的slave my.cnf配置文件
[client]
character-set-server = utf8
port = 3306
socket = /tmp/mysql.sock
[mysqld]
character-set-server = utf8
replicate-ignore-db = mysql
replicate-ignore-db = test
replicate-do-db = blog
replicate-ignore-db = information_schema
user = mysql
port = 3306
socket = /tmp/mysql.sock
basedir = /usr/local/webserver/mysql
datadir = /media/raid10/mysql/3306/data
log-error = /media/raid10/mysql/3306/mysql_error.log
pid-file = /media/raid10/mysql/3306/mysql.pid
open_files_limit = 10240
back_log = 600
max_connections = 5000
max_connect_errors = 6000
table_cache = 614
external-locking = FALSE
max_allowed_packet = 16M
sort_buffer_size = 1M
join_buffer_size = 1M
thread_cache_size = 300
#thread_concurrency = 8
query_cache_size = 20M
query_cache_limit = 2M
query_cache_min_res_unit = 2k
default-storage-engine = MyISAM
thread_stack = 192K
transaction_isolation = READ-COMMITTED
tmp_table_size = 20M
max_heap_table_size = 20M
long_query_time = 3
log-slave-updates
log-bin = /media/raid10/mysql/3306/binlog/binlog
binlog_cache_size = 4M
binlog_format = MIXED
max_binlog_cache_size = 8M
max_binlog_size = 20M
relay-log-index = /media/raid10/mysql/3306/relaylog/relaylog
relay-log-info-file = /media/raid10/mysql/3306/relaylog/relaylog
relay-log = /media/raid10/mysql/3306/relaylog/relaylog
expire_logs_days = 30
key_buffer_size = 10M
read_buffer_size = 1M
read_rnd_buffer_size = 6M
bulk_insert_buffer_size = 4M
myisam_sort_buffer_size = 8M
myisam_max_sort_file_size = 20M
myisam_repair_threads = 1
myisam_recover
interactive_timeout = 120
wait_timeout = 120
skip-name-resolve
#master-connect-retry = 60
slave-skip-errors = 1032,1062,126,1114,1146,1048,1396
#master-host=172.29.141.112
#master-user = admin
#master-password = 12345678
#master-port = 3306
server-id = 2
innodb_additional_mem_pool_size = 16M
innodb_buffer_pool_size = 20M
innodb_data_file_path = ibdata1:56M:autoextend
innodb_file_io_threads = 4
innodb_thread_concurrency = 8
innodb_flush_log_at_trx_commit = 2
innodb_log_buffer_size = 16M
innodb_log_file_size = 20M
innodb_log_files_in_group = 3
innodb_max_dirty_pages_pct = 90
innodb_lock_wait_timeout = 120
innodb_file_per_table = 0
#log-slow-queries = /media/raid10/mysql/3306/slow.log
#long_query_time = 10
[mysqldump]
quick
max_allowed_packet = 32M
六.通过查看master的状态(在master上查看)，为配置slave做准备
mysql> show master status/G;
ERROR 2006 (HY000): MySQL server has gone away
No connection. Trying to reconnect...
Connection id: 13
Current database: blog
*************************** 1. row ***************************
File: binlog.000005
Position: 592
Binlog_Do_DB: blog
Binlog_Ignore_DB: mysql
1 row in set (0.01 sec)
ERROR:
No query specified
从上面的信息，可以看出，master现在使用的binlog是binlog.000005，position是592,那么下面的slave配置必须与这个对应。
其实binlog.000005是当前master使用的binlog日志文件
position是当前master使用的binlog.000005日志文件的位置
简单理解为master正在使用哪个binlog的哪个数据行(位置)。
七.如果是5.5.3-m3版本mysql,需要启动slave后，配置与master相关对应的信息(在slave上配置)
注意，这个与第六步相对应
mysql> stop slave ;
mysql> change master to master_host='172.29.141.112', master_user='admin', master_password='12345678', master_log_file='binlog.000005', master_log_pos=488;
mysql> CHANGE MASTER TO MASTER_CONNECT_RETRY=60;
这个与5.0的配置my.cnf作用是一样的，配置成与master相对应的内容
主要是配置slave，让slave知道从master的哪个binlog上的哪个位置复制数据。所以需要知道master的ip,user_name,user_passwd,binlog,binlog_position以及多长时间连接一次master
八.开启slave
mysql> start slave;
九.解除master只读限制,并做测试
mysql> unlock tables;
mysql> use blog;
mysql> create longxibendi ( a int, b int );
十.从slave上查看
mysql> use blog;
mysql> show tables;
+-----------------------+
| Tables_in_blog |
+-----------------------+
| longxibendi |
| wp_commentmeta |
| wp_comments |
| wp_links |
| wp_options |
| wp_postmeta |
| wp_posts |
| wp_term_relationships |
| wp_term_taxonomy |
| wp_terms |
| wp_usermeta |
| wp_users |
+-----------------------+
12 rows in set (0.00 sec)
可以看到成功了！！
十一.配置过程中，可以用 show slave status/G; 在 slave上
查看 slave的复制情况
十二.如果出现什么问题，可能是防火墙的问题
/etc/init.d/iptables stop 关闭 master 上的防火墙，或者进行相应的配置
十三.常遇到的错误
1.[mysql]ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2)
这个错误，网上有很多说法，其实直接的原因是mysql服务器没有启动
之前我按照5.0x配置master-slave，然后启动slave，在连接slave,就会报这个错误
后来发现原因是，mysql slave没有启动起来，然后去查错误日志，发现以下的字段
110505 01:55:20 mysqld_safe mysqld from pid file /media/raid10/mysql/3306/mysql.pid ended
110505 02:04:41 mysqld_safe Starting mysqld daemon with databases from /media/raid10/mysql/3306/data
InnoDB: The InnoDB memory heap is disabled
InnoDB: Mutexes and rw_locks use InnoDB's own implementation
110505 2:04:41 InnoDB: highest supported file format is Barracuda.
110505 2:04:41 InnoDB Plugin 1.0.6 started; log sequence number 44338
110505 2:04:41 [ERROR] /usr/local/webserver/mysql/libexec/mysqld: unknown variable 'master-connect-retry=60'
110505 2:04:41 [ERROR] Aborting
110505 2:04:41 InnoDB: Starting shutdown...
110505 2:04:43 InnoDB: Shutdown completed; log sequence number 44348
110505 2:04:43 [Note] /usr/local/webserver/mysql/libexec/mysqld: Shutdown complete
110505 02:04:43 mysqld_safe mysqld from pid file /media/raid10/mysql/3306/mysql.pid ended
110505 02:07:44 mysqld_safe Starting mysqld daemon with databases from /media/raid10/mysql/3306/data
InnoDB: The InnoDB memory heap is disabled
InnoDB: Mutexes and rw_locks use InnoDB's own implementation
110505 2:07:44 InnoDB: highest supported file format is Barracuda.
110505 2:07:45 InnoDB Plugin 1.0.6 started; log sequence number 44348
110505 2:07:45 [ERROR] /usr/local/webserver/mysql/libexec/mysqld: unknown variable 'master-host=172.29.141.112'
110505 2:07:45 [ERROR] Aborting
从上面的ERROR，知道 master-connect-retry=60这个my.cnf中的参数有问题，后来从网上搜资料，发现，mysql5.5.3-m3版本不支持这个参数，
然后我把这个参数注释掉，又发现不支持这个参数master-host，从上面的ERROR字段可以看出来。后来，就知道，5.5.3-m3不能按5.0.x那样配置
原来不需要从my.cnf中配置master相关信息，当然server-id是必须的。其他信息，通过 在命令行中 ，登陆 mysql服务器配置。
其实server-id的作用是
第一，标识，区分不同的slave,第二，防止环备份的发生
2.Last_Error: Last_SQL_Error：等错误
这个是从 slave上，运行 show slave status/G; 得到的。出现这个问题，最根本的原因是，slave 没有与当前的master的binlog 和binlog的position对应上
也就是说，slave传输的master binlog 不与当前master正使用的binlog以及binlog的行数对应。
3.[ERROR] Slave I/O: error connecting to master 'admin@172.29.141.112:3306' - retry-time: 60 retries: 86400, Error_code: 2003
这个就是因为防火墙的问题，所以用 /etc/init.d/iptables stop 关闭防火墙就OK了。
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