mysql 主从的几个参数
log-slave-updates 级联复制 配合--log-bin一起使用
master-connect-retry 主库失联重试时间
read-only 只读
replicate-do-db
replicate-do-table
replicate-ignore-db
replicate-ignore-table
replicate-wild-do-table
slave-skip-errors 自动跳过错误号
让主库停下来，从库追一下：
主库：
mysql> flush tables with read lock;
Query OK, 0 rows affected (0.00 sec)
mysql> show master status;
+----------------------+----------+--------------+------------------+-------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+----------------------+----------+--------------+------------------+-------------------+
| mysql3306-bin.000012 | 1166 | | | |
+----------------------+----------+--------------+------------------+-------------------+
1 row in set (0.00 sec)
mysql>
从库：
mysql> select master_pos_wait('mysql3306-bin.000012','1166');
+------------------------------------------------+
| master_pos_wait('mysql3306-bin.000012','1166') |
+------------------------------------------------+
| 0 |
+------------------------------------------------+
1 row in set (0.00 sec)
mysql>
这个select语句会阻塞直到从库达到指定的日志文件和偏移量，查询返回0，则主从同步。
主库：
mysql> unlock tables;
Query OK, 0 rows affected (0.00 sec)
mysql> set global sql_slave_skip_counter = N 跳过主库的两个更新语句
解决log event entry exceeded max_allowed_packet的处理
主从库上增加；
mysql> show variables like "%max_allowed_packet%";
+--------------------------+------------+
| Variable_name | Value |
+--------------------------+------------+
| max_allowed_packet | 4194304 |
| slave_max_allowed_packet | 1073741824 |
+--------------------------+------------+
2 rows in set (0.00 sec)
mysql> set @@global.max_allowed_packet = 16777216;
Query OK, 0 rows affected (0.00 sec)
mysql>
自增长变量的解决
master1：auto_increment_increment = 2，auto_increment_offset = 1；（1，3，5，7）
master2：auto_increment_increment = 2，auto_increment_offset = 0；（2，4，6，8）
实例：
mysql> create table auto_table(id int(5) not null auto_increment,num int(2) ,primary key (id));
Query OK, 0 rows affected (0.34 sec)
mysql> show variables like "%auto_increment%";
+--------------------------+-------+
| Variable_name | Value |
+--------------------------+-------+
| auto_increment_increment | 1 |
| auto_increment_offset | 1 |
+--------------------------+-------+
2 rows in set (0.00 sec)
mysql> set session auto_increment_increment = 20;
Query OK, 0 rows affected (0.00 sec)
mysql> set session auto_increment_offset = 7;
Query OK, 0 rows affected (0.00 sec)
mysql> show variables like "%auto_increment%";
+--------------------------+-------+
| Variable_name | Value |
+--------------------------+-------+
| auto_increment_increment | 20 |
| auto_increment_offset | 7 |
+--------------------------+-------+
2 rows in set (0.00 sec)
mysql>
mysql> insert into auto_table(num) values(1),(2);
Query OK, 2 rows affected (0.14 sec)
Records: 2 Duplicates: 0 Warnings: 0
mysql> insert into auto_table(num) values(3),(4);
Query OK, 2 rows affected (0.25 sec)
Records: 2 Duplicates: 0 Warnings: 0
mysql> select * from auto_table;
+----+------+
| id | num |
+----+------+
| 7 | 1 |
| 27 | 2 |
| 47 | 3 |
| 67 | 4 |
+----+------+
4 rows in set (0.00 sec)
mysql>
从7开始每次加20.
mysql> alter table auto_table add column createtime datetime;
Query OK, 0 rows affected (0.62 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> insert into auto_table(num,createtime) values(5,now()) ;
Query OK, 1 row affected (0.04 sec)
mysql> select * from auto_table;
+----+------+---------------------+
| id | num | createtime |
+----+------+---------------------+
| 7 | 1 | NULL |
| 27 | 2 | NULL |
| 47 | 3 | NULL |
| 67 | 4 | NULL |
| 87 | 5 | 2016-05-10 18:32:18 |
+----+------+---------------------+
5 rows in set (0.00 sec)
mysql>
如何提高复制的性能：
通过拆分减少一个从库上需要数据同步的表来解决，不同的从库复制不同的库。
从库并行更新，从库更新时启动多个SQL线程。
mysql> show variables like "%workers%";
+------------------------+-------+
| Variable_name | Value |
+------------------------+-------+
| slave_parallel_workers | 0 |
+------------------------+-------+
1 row in set (0.00 sec)
mysql> set global slave_parallel_workers = 2;
Query OK, 0 rows affected (0.00 sec)
mysql> show variables like "%workers%";
+------------------------+-------+
| Variable_name | Value |
+------------------------+-------+
| slave_parallel_workers | 2 |
+------------------------+-------+
1 row in set (0.00 sec)