以前抽空做的MySQL 的主主同步。
不過心理做好准備，對性能會有一定的影響！
把步驟寫下來，至於會出現的什麼問題，以後隨時更新。這裡我同步的數據庫是TEST
1、環境描述。
主機：192.168.0.231（A）
主機：192.168.0.232（B）
MySQL 版本為5.1.21
2、授權用戶。
A：
MySQL> grant replication slave,file on *.* to 'repl1'@'192.168.0.232' identifIEd
by '123456';
Query OK, 0 rows affected (0.00 sec)
MySQL> flush privileges;
Query OK, 0 rows affected (0.00 sec)
B：
MySQL> grant replication slave,file on *.* to 'repl2'@'192.168.0.231' identifIEd
by '123456';
Query OK, 0 rows affected (0.00 sec)
MySQL> flush privileges;
Query OK, 0 rows affected (0.00 sec)
然後都停止MySQL 服務器。
3、配置文件。
在兩個機器上的my.cnf裡面都開啟二進制日志 。
A：
user = MySQL
log-bin=MySQL-bin
server-id = 1
binlog-do-db=test
binlog-ignore-db=MySQL
replicate-do-db=test
replicate-ignore-db=MySQL
log-slave-updates
slave-skip-errors=all
sync_binlog=1
auto_increment_increment=2
auto_increment_offset=1
B：
user = MySQL
log-bin=MySQL-bin
server-id = 2
binlog-do-db=test
binlog-ignore-db=MySQL
replicate-do-db=test
replicate-ignore-db=MySQL
log-slave-updates
slave-skip-errors=all
sync_binlog=1
auto_increment_increment=2
auto_increment_offset=2
至於這些參數的說明具體看手冊。
紅色的部分非常重要，如果一個MASTER 掛掉的話，另外一個馬上接管。
紫紅色的部分指的是服務器頻繁的刷新日志。這個保證了在其中一台掛掉的話，日志刷新到另外一台。從而保證了數據的同步 。
4、重新啟動MySQL服務器。
在A和B上執行相同的步驟
[root@localhost ~]# /usr/local/mysql/bin/MySQLd_safe &
[1] 4264
[root@localhost ~]# 071213 14:53:20 mysqld_safe Logging to '/usr/local/MySQL/data/localhost.localdomain.err'.
/usr/local/mysql/bin/MySQLd_safe: line 366: [: -eq: unary Operator expected
071213 14:53:20 mysqld_safe Starting mysqld daemon with databases from /usr/local/MySQL/data
5、進入MySQL的SHELL。
A：
MySQL> flush tables with read lock\G
Query OK, 0 rows affected (0.00 sec)
MySQL> show master status\G
*************************** 1. row ***************************
File: MySQL-bin.000007
Position: 528
Binlog_Do_DB: test
Binlog_Ignore_DB: MySQL
1 row in set (0.00 sec)
B：
MySQL> flush tables with read lock;
Query OK, 0 rows affected (0.00 sec)
MySQL> show master status\G
*************************** 1. row ***************************
File: MySQL-bin.000004
Position: 595
Binlog_Do_DB: test
Binlog_Ignore_DB: MySQL
1 row in set (0.00 sec)
然後備份自己的數據，保持兩個機器的數據一致。
方法很多。完了後看下一步。
6、在各自機器上執行CHANGE MASTER TO命令。
A：
MySQL> change master to
-> master_host='192.168.0.232',
-> master_user='repl2',
-> master_passWord='123456',
-> master_log_file='MySQL-bin.000004',
-> master_log_pos=595;
Query OK, 0 rows affected (0.01 sec)
MySQL> start slave;
Query OK, 0 rows affected (0.00 sec)
B：
MySQL> change master to
-> master_host='192.168.0.231',
-> master_user='repl1',
-> master_passWord='123456',
-> master_log_file='MySQL-bin.000007',
-> master_log_pos=528;
Query OK, 0 rows affected (0.01 sec)
MySQL> start slave;
Query OK, 0 rows affected (0.00 sec)
7、查看各自機器上的IO進程和 SLAVE進程是否都開啟。
A：
MySQL> show processlist\G
*************************** 1. row ***************************
Id: 2
User: repl
Host: 192.168.0.232:54475
db: NULL
Command: Binlog Dump
Time: 1590
State: Has sent all binlog to slave; waiting for binlog to be updated
Info: NULL
*************************** 2. row ***************************
Id: 3
User: system user
Host:
db: NULL
Command: Connect
Time: 1350
State: Waiting for master to send event
Info: NULL
*************************** 3. row ***************************
Id: 4
User: system user
Host:
db: NULL
Command: Connect
Time: 1149
State: Has read all relay log; waiting for the slave I/O thread to update it
Info: NULL
*************************** 4. row ***************************
Id: 5
User: root
Host: localhost
db: test
Command: Query
Time: 0
State: NULL
Info: show processlist
4 rows in set (0.00 sec)
B：
MySQL> show processlist\G
*************************** 1. row ***************************
Id: 1
User: system user
Host:
db: NULL
Command: Connect
Time: 2130
State: Waiting for master to send event
Info: NULL
*************************** 2. row ***************************
Id: 2
User: system user
Host:
db: NULL
Command: Connect
Time: 1223
State: Has read all relay log; waiting for the slave I/O thread to update it
Info: NULL
*************************** 3. row ***************************
Id: 4
User: root
Host: localhost
db: test
Command: Query
Time: 0
State: NULL
Info: show processlist
*************************** 4. row ***************************
Id: 5
User: repl2
Host: 192.168.0.231:50718
db: NULL
Command: Binlog Dump
Time: 1398
State: Has sent all binlog to slave; waiting for binlog to be updated
Info: NULL
4 rows in set (0.00 sec)
如果紅色部分沒有出現，檢查DATA目錄下的錯誤文件。
8、釋放掉各自的鎖，然後進行插數據測試。
MySQL> unlock tables;
Query OK, 0 rows affected (0.00 sec)
插入之前兩個機器表的對比：
A：
MySQL> show tables;
+----------------+
| Tables_in_test |
+----------------+
| t11_innodb |
| t22 |
+----------------+
B：
MySQL> show tables;
+----------------+
| Tables_in_test |
+----------------+
| t11_innodb |
| t22 |
+----------------+
從A機器上進行插入
A：
MySQL> create table t11_replicas
-> (id int not null auto_increment primary key,
-> str varchar(255) not null) engine myisam;
Query OK, 0 rows affected (0.01 sec)
MySQL> insert into t11_replicas(str) values
-> ('This is a master to master test table');
Query OK, 1 row affected (0.01 sec)
MySQL> show tables;
+----------------+
| Tables_in_test |
+----------------+
| t11_innodb |
| t11_replicas |
| t22 |
+----------------+
3 rows in set (0.00 sec)
MySQL> select * from t11_replicas;
+----+---------------------------------------+
| id | str |
+----+---------------------------------------+
| 1 | This is a master to master test table |
+----+---------------------------------------+
1 row in set (0.00 sec)
現在來看B機器：
MySQL> show tables;
+----------------+
| Tables_in_test |
+----------------+
| t11_innodb |
| t11_replicas |
| t22 |
+----------------+
3 rows in set (0.00 sec)
MySQL> select * from t11_replicas;
+----+---------------------------------------+
| id | str |
+----+---------------------------------------+
| 1 | This is a master to master test table |
+----+---------------------------------------+
1 row in set (0.00 sec)
現在反過來從B機器上插入數據：
B：
MySQL> insert into t11_replicas(str) values('This is a test 2');
Query OK, 1 row affected (0.00 sec)
MySQL> select * from t11_replicas;
+----+---------------------------------------+
| id | str |
+----+---------------------------------------+
| 1 | This is a master to master test table |
| 2 | This is a test 2 |
+----+---------------------------------------+
2 rows in set (0.00 sec)
我們來看A
A：
MySQL> select * from t11_replicas;
+----+---------------------------------------+
| id | str |
+----+---------------------------------------+
| 1 | This is a master to master test table |
| 2 | This is a test 2 |
+----+---------------------------------------+
2 rows in set (0.00 sec)
好了。現在兩個表互相為MASTER。
多MASTER自增字段沖突的問題。
