mysql双主复制实践
mysql双主复制实践
一、原理介绍
要讲清楚mysql的双主复制，先说一下主从复制的原理：
主点只负责写，节点只负责读，当用户写请求到达后，被调到主节点，写操作完成后将记录在主节点的二进制日志中，从节点启动I/O线程从主节点处请求主节点的二进制日志，主节点通过dump线程接收到此请求后将二进制日志发送给从节点。而后从节点将收到的二进制日志通过SQL线程在中继日志中，实现事件重放。
主节点：
启动dump线程：为每个从节点启动一个dump线程，用于发送二进制文件
从节点：
启动I/O线程：从主节点请求二进制日志，并保存在中继日志中
启动SQL线程：从中继日志中读取日志事件，实现重放
而什么是双主呢？双主即两个mysql服务器互为主从关系，即在A服务器眼里自己是主服务器而B是从服务器，在B服务器眼里自己是主服务器而A是从服务器。
接下来以两台服务器来演示整个配置过程
A服务器：node1 192.168.50.138
B服务器：node2 192.168.50.139
二、配置A服务器
配置步骤：
1、配置唯一serverID，启用二进制日志，启用中继日志
[root@node1 ~]# vim /etc/my.cnf
[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
# Disabling symbolic-links is recommended to prevent assorted security risks
symbolic-links=0
# Settings user and group are ignored when systemd is used.
# If you need to run mysqld under a different user or group,
# customize your systemd unit file for mariadb according to the
# instructions in http://fedoraproject.org/wiki/Systemd
skip_name_resolve = on #跳过主机名反解
innodb_file_per_table = on #没张表使用一个表空间来存储
log_bin=mysql-bin #开启二进制日志，命名为mysql-bin
server_id = 1 #serverID号为1
relay_log = relay-log #开启中继日志，命名为relay-log
[mysqld_safe]
log-error=/var/log/mariadb/mariadb.log
pid-file=/var/run/mariadb/mariadb.pid
#
# include all files from the config directory
#
!includedir /etc/my.cnf.d
2、创建具有相应权限的用户账号
权限：REPLICATION SLAVE , REPLICATION CLIENT
MariaDB [(none)]> GRANT REPLICATION SLAVE,REPLICATION CLIENT ON *.* TO 'repl-node1'@'192.168.50.139' IDENTIFIED BY '123456';三、配置B服务器
1、配置唯一serverID，启用二进制日志，启用中继日志
[root@node2 ~]# vim /etc/my.cnf
[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
# Disabling symbolic-links is recommended to prevent assorted security risks
symbolic-links=0
# Settings user and group are ignored when systemd is used.
# If you need to run mysqld under a different user or group,
# customize your systemd unit file for mariadb according to the
# instructions in http://fedoraproject.org/wiki/Systemd
skip_name_resolve = on
innodb_file_per_table = on
log-bin=mysql-bin
server_id = 2 #注意一定要是全局唯一的serverID
relay_log = relay-log
[mysqld_safe]
log-error=/var/log/mariadb/mariadb.log
pid-file=/var/run/mariadb/mariadb.pid
#
# include all files from the config directory
#
!includedir /etc/my.cnf.d2、创建具有相应权限的用户账号
权限：REPLICATION SLAVE , REPLICATION CLIENT
MariaDB [(none)]> GRANT REPLICATION SLAVE,REPLICATION CLIENT ON *.* TO 'repl-node2'@'192.168.50.138' IDENTIFIED BY '123456';四、配置互为主从
分别查看A、B主机的master状态，和起始位置
A:
MariaDB [(none)]> SHOW MASTER STATUS;
+------------------+----------+--------------+------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+------------------+----------+--------------+------------------+
| mysql-bin.000003 | 425 | | |
+------------------+----------+--------------+------------------+
1 row in set (0.00 sec)
B：
MariaDB [(none)]> SHOW MASTER STATUS;
+------------------+----------+--------------+------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+------------------+----------+--------------+------------------+
| mysql-bin.000003 | 425 | | |
+------------------+----------+--------------+------------------+
1 row in set (0.00 sec)将A作为从节点指向B为主节点
MariaDB [(none)]> CHANGE MASTER TO MASTER_HOST='192.168.50.139', MASTER_USER='repl-node2', MASTER_PASSWORD='123456', MASTER_LOG_FILE='mysql-bin.000003', MASTER_LOG_POS = 425;
Query OK, 0 rows affected (0.08 sec)将B作为从节点指向A为主节点
MariaDB [(none)]> CHANGE MASTER TO MASTER_HOST='192.168.50.138', MASTER_USER='repl-node1', MASTER_PASSWORD='123456', MASTER_LOG_FILE='mysql-bin.000003', MASTER_LOG_POS = 425;现在来看看ASLAVE状态
A：
MariaDB [(none)]> SHOW SLAVE STATUS\G;
*************************** 1. row ***************************
Slave_IO_State:
Master_Host: 192.168.50.139 #指明主节点是node2
Master_User: repl-node2
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000003 #指明主节点的二进制文件
Read_Master_Log_Pos: 425 #事件起始位置
Relay_Log_File: relay-log.000001 #从节点自己的中继日志
Relay_Log_Pos: 4 #中继日志起始位置
Relay_Master_Log_File: mysql-bin.000003
Slave_IO_Running: No #还未启动IO线程
Slave_SQL_Running: No #还未启动SQL线程
Replicate_Do_DB:
Replicate_Ignore_DB:
Replicate_Do_Table:
Replicate_Ignore_Table:
Replicate_Wild_Do_Table:
Replicate_Wild_Ignore_Table:
Last_Errno: 0
Last_Error:
Skip_Counter: 0
Exec_Master_Log_Pos: 425
Relay_Log_Space: 245
Until_Condition: None
Until_Log_File:
Until_Log_Pos: 0
Master_SSL_Allowed: No
Master_SSL_CA_File:
Master_SSL_CA_Path:
Master_SSL_Cert:
Master_SSL_Cipher:
Master_SSL_Key:
Seconds_Behind_Master: NULL
Master_SSL_Verify_Server_Cert: No
Last_IO_Errno: 0
Last_IO_Error:
Last_SQL_Errno: 0
Last_SQL_Error:
Replicate_Ignore_Server_Ids:
Master_Server_Id: 0分别开启各复制线程
MariaDB [(none)]> START SLAVE; #A和B中都执行
Query OK, 0 rows affected (0.00 sec)现在看看A中有哪些数据
MariaDB [(none)]> SHOW DATABASES;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| test |
+--------------------+在A中创建个mydb数据库，在数据库中创建student表，看B中能否实现同步复制
MariaDB [(none)]> CREATE DATABASE mydb;
Query OK, 1 row affected (0.00 sec)
MariaDB [(none)]> USE mydb;
Database changed
MariaDB [mydb]> CREATE TABLE student (name VARCHAR(30) NOT NULL,class INT NOT NULL);
Query OK, 0 rows affected (0.01 sec)
MariaDB [mydb]> INSERT INTO student VALUES ('xiaoming',10),('xiaogouzi',100);
Query OK, 2 rows affected (0.01 sec)
Records: 2 Duplicates: 0 Warnings: 0在B中进行查看
MariaDB [(none)]> SHOW DATABASES;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mydb |
| mysql |
| performance_schema |
| test |
+--------------------+
5 rows in set (0.00 sec)
MariaDB [(none)]> USE mydb
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
MariaDB [mydb]> SELECT * FROM student;
+-----------+-------+
| name | class |
+-----------+-------+
| xiaoming | 10 |
| xiaogouzi | 100 |
+-----------+-------+
2 rows in set (0.00 sec)
B中已经能够看到从A中执行的操作，现在从B中插入一行数据，看A中是否能同步到
MariaDB [mydb]> INSERT INTO student VALUES ('laowang',50);
Query OK, 1 row affected (0.00 sec)在A中查看
MariaDB [mydb]> SELECT * FROM student;
+-----------+-------+
| name | class |
+-----------+-------+
| xiaoming | 10 |
| xiaogouzi | 100 |
| laowang | 50 |
+-----------+-------+
3 rows in set (0.00 sec)成功！！！