詳細介紹MySQL如何開啓主從複製實現數據同步

---

主從複製原理

主從複製線程

主節點

   dump Thread：爲每個Slave的I/O Thread啓動一個dump線程，用於向其發送binary log events

從節點

   I/O Thread：向Master請求二進制日誌事件，並保存於中繼日誌中
   SQL Thread：從中繼日誌中讀取日誌事件，在本地完成重放

跟複製功能相關的文件

   master.info：用於保存slave連接至master時的相關信息，例如賬號、密碼、服務器地址等

   relay-log.info：保存在當前slave節點上已經複製的當前二進制日誌和本地replay log日誌的對應關係

主從複製特點

   異步複製
   主從數據不一致比較常見

複製架構

   Master/Slave,Master/Master,環狀複製
   一主多從
   從服務器還可以再有從服務器
   一從多主：適用於多個不同數據庫

複製需要考慮二進制日誌時間記錄格式

   STATEMENT（5.0之前）
   ROW（5.1之後，推薦）
   MIXED

搭建環境準備

主機	IP地址	類型
CentOS7.6	192.168.36.101	Master
CentOS7.6	192.168.36.103	Slave
CentOS7.6	192.168.36.104	Slave

搭建之前請先確保MySQL軟件包已經安裝

一主一從

Master節點修改數據庫配置文件

[root@Master ~]#cat /etc/my.cnf
[mysqld]
server_id=1     # 爲Master節點設置一個全局唯一的ID號
binlog_format=row       # 基於行復制的數據庫語句
log-bin=/data/bin/mysql-bin     # 啓用二進制日誌

重新啓動數據庫服務

[root@Master ~]#service mysqld restart
Restarting mysqld (via systemctl):                         [  OK  ]

Master節點上創建帶有複製權限的用戶賬號

MariaDB [(none)]> grant replication slave on *.* to repluser@'192.168.36.%' identified by 'centos';
Query OK, 0 rows affected (0.00 sec)

查看Master的日誌位置信息

MariaDB [mysql]> show master logs;
+------------------+-----------+
| Log_name         | File_size |
+------------------+-----------+
| mysql-bin.000001 |    912372 |
+------------------+-----------+
1 row in set (0.00 sec)

Slave節點修改配置文件

[root@Slave-1 ~]#cat /etc/my.cnf
[mysqld]
server_id=2         # Slave節點設置全局唯一的ID號
read_only           # 只讀

重新啓動數據庫服務

[root@Slave-1 ~]#systemctl restart mariadb

使用Master創建的複製權限的用戶賬號進行同步

MariaDB [(none)]> CHANGE MASTER TO
    -> MASTER_HOST='192.168.36.101',
    ->  MASTER_USER='repluser',
    ->  MASTER_PASSWORD='centos',
    ->  MASTER_PORT=3306,
    ->  MASTER_LOG_FILE='mysql-bin.000001',
    ->  MASTER_LOG_POS=245;
Query OK, 0 rows affected (0.01 sec)

啓動Slave線程

MariaDB [(none)]> slave start;
Query OK, 0 rows affected (0.00 sec)

查看線程是否啓動

*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.36.101
                  Master_User: repluser
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-bin.000001
          Read_Master_Log_Pos: 7389
               Relay_Log_File: mariadb-relay-bin.000002
                Relay_Log_Pos: 7673
        Relay_Master_Log_File: mysql-bin.000001
             Slave_IO_Running: Yes      # 從節點的IO線程
            Slave_SQL_Running: Yes      # 從節點的SQL線程
....
        Seconds_Behind_Master: 0        # Master與SLave服務器差別延遲
.....
             Master_Server_Id: 1
1 row in set (0.00 sec)

檢查數據同步情況

MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| hellodb            |
| mysql              |
| performance_schema |
| test               |
+--------------------+
5 rows in set (0.00 sec)

主節點中查看數據庫的線程

MariaDB [hellodb]> show processlist;
+----+----------+----------------------+---------+-------------+------+------------------------------------------------------------------
| Id | User     | Host                 | db      | Command     | Time | State
+----+----------+----------------------+---------+-------------+------+------------------------------------------------------------------
|  3 | root     | localhost            | hellodb | Query       |    0 | NULL
|  6 | repluser | 192.168.36.103:51516 | NULL    | Binlog Dump |  115 | Master has sent all binlog to slave; waiting for binlog to be upd
+----+----------+----------------------+---------+-------------+------+------------------------------------------------------------------
2 rows in set (0.00 sec)

從節點中查看數據庫的線程

MariaDB [(none)]> show processlist;
+----+-------------+-----------+------+---------+-------+-----------------------------------------------------------------------------+--
| Id | User        | Host      | db   | Command | Time  | State                                                                       | I
+----+-------------+-----------+------+---------+-------+-----------------------------------------------------------------------------+--
|  4 | root        | localhost | NULL | Query   |     0 | NULL                                                                        | s
|  5 | system user |           | NULL | Connect |   159 | Waiting for master to send event                                            | N
|  6 | system user |           | NULL | Connect | 29259 | Slave has read all relay log; waiting for the slave I/O thread to update it | N
+----+-------------+-----------+------+---------+-------+-----------------------------------------------------------------------------+--
3 rows in set (0.00 sec)

一主多從：新添加一個從節點

Slave-2 節點安裝數據庫服務

[root@Slave-2 ~]#yum install -y mariadb-server

修改 Slave-2 節點配置文件

[root@Slave-2 ~]#cat /etc/my.cnf
[mysqld]
server_id=3
read_only
....

重新啓動 Slave-2 節點數據庫服務

[root@Slave-2 ~]#systemctl restart mariadb

Slave-2 節點配置同步信息

MariaDB [(none)]> CHANGE MASTER TO
    -> MASTER_HOST='192.168.36.101',
    ->  MASTER_USER='repluser',
    ->  MASTER_PASSWORD='centos',
    ->  MASTER_PORT=3306,
    ->  MASTER_LOG_FILE='mysql-bin.000001',
    ->  MASTER_LOG_POS=245;
Query OK, 0 rows affected (0.00 sec)

啓用線程

MariaDB [(none)]> slave start;
Query OK, 0 rows affected (0.00 sec)

檢查同步情況

MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| hellodb            |
| mysql              |
| performance_schema |
| test               |
+--------------------+
6 rows in set (0.00 sec)

主主複製：兩臺服務器互爲主從

主機	IP地址	類型
CentOS7.6	192.168.36.101	Master-1
CentOS7.6	192.168.36.103	Master-2

Master-1 修改配置文件

[root@Master-1 data]#cat /etc/my.cnf
[mysqld]
server_id=1
log_bin     # 啓用日誌

# 爲避免ID衝突問題，需要添加下面兩行配置：Master-1 爲奇數增長，Master-2 爲偶數增長
auto_increment_offset=1     # 開始點
auto_increment_increment=2  # 增長幅度
....

Master-2 修改配置文件

[root@Master-2 data]#cat /etc/my.cnf
[mysqld]
server_id=2
log_bin
auto_increment_offset=2
auto_increment_increment=2

重新啓動服務

[root@Master-1 ~]#systemctl restart mariadb
[root@Master-2 ~]#systemctl restart mariadb

Master-1 創建權限用戶，Master-2 先設置爲從服務器進行同步 Master-1 的數據庫

MariaDB [(none)]> grant replication slave on *.* to repluser@'192.168.36.%' identified by 'centos';
Query OK, 0 rows affected (0.00 sec)

Master-2 同步Master-1

MariaDB [(none)]> CHANGE MASTER TO
    -> MASTER_HOST='192.168.36.101',
    ->  MASTER_USER='repluser',
    ->  MASTER_PASSWORD='centos',
    ->  MASTER_PORT=3306,
    ->  MASTER_LOG_FILE='mysql-bin.000001',
    ->  MASTER_LOG_POS=245;
Query OK, 0 rows affected (0.00 sec)

啓用線程

MariaDB [(none)]> slave start;
Query OK, 0 rows affected (0.00 sec)

檢查同步情況

MariaDB [(none)]> use mysql;
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 [mysql]> select user,password,host from user;
+----------+-------------------------------------------+--------------+
| user     | password                                  | host         |
+----------+-------------------------------------------+--------------+
| root     |                                           | localhost    |
| root     |                                           | 127.0.0.1    |
| root     |                                           | ::1          |
| repluser | *128977E278358FF80A246B5046F51043A2B1FCED | 192.168.36.% |
+----------+-------------------------------------------+--------------+
7 rows in set (0.00 sec)

Master-1 向 Master-2 進行同步

MariaDB [mysql]> CHANGE MASTER TO
    -> MASTER_HOST='192.168.36.103',
    -> MASTER_USER='repluser',
    -> MASTER_PASSWORD='centos',
    -> MASTER_PORT=3306,
    -> MASTER_LOG_FILE='mysql-bin.000001',
    -> MASTER_LOG_POS=245;
Query OK, 0 rows affected (0.05 sec)

Master-1 同步狀態

MariaDB [(none)]> show slave status\G;
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.36.103
                  Master_User: repluser
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-bin.000001
          Read_Master_Log_Pos: 245
               Relay_Log_File: mariadb-relay-bin.000003
                Relay_Log_Pos: 529
        Relay_Master_Log_File: mysql-bin.000001
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
....
           Master_SSL_Allowed: No
....
             Master_Server_Id: 2
1 row in set (0.01 sec)

此時Master-1、Master-2 實現主主複製功能

半同步複製

   半同步複製的作用是：主服務器宕機後，所有備份服務器主動向同步數據最多的服務器進行數據的同步，以確保數據損失降到最低。

半同步是通過插件功能達成的

Master節點安裝semisync_master.so插件

MariaDB [db1]> INSTALL PLUGIN rpl_semi_sync_master SONAME 'semisync_master.so';
Query OK, 0 rows affected (0.07 sec)

啓用插件功能

MariaDB [db1]> SET GLOBAL rpl_semi_sync_master_enabled=1;
Query OK, 0 rows affected (0.00 sec)

設置超時時長

MariaDB [db1]> SET GLOBAL rpl_semi_sync_master_timeout=6000;
Query OK, 0 rows affected (0.00 sec)

查看Master插件狀態

MariaDB [db1]> show variables like '%semi%';
+------------------------------------+-------+
| Variable_name                      | Value |
+------------------------------------+-------+
| rpl_semi_sync_master_enabled       | ON    |
| rpl_semi_sync_master_timeout       | 6000  |
| rpl_semi_sync_master_trace_level   | 32    |
| rpl_semi_sync_master_wait_no_slave | ON    |
+------------------------------------+-------+
4 rows in set (0.00 sec)

Master修改配置文件並重啓數據庫服務

[root@Master data]#cat /etc/my.cnf
[mysqld]
...
rpl_semi_sync_master_enabled        # 啓用插件功能
...

[root@Master data]#systemctl restart mariadb

Slave節點安裝semisync_slave.so插件

MariaDB [db1]> INSTALL PLUGIN rpl_semi_sync_slave SONAME 'semisync_slave.so';
Query OK, 0 rows affected (0.00 sec)

啓用slave插件功能

MariaDB [db1]> SET GLOBAL rpl_semi_sync_slave_enabled=1;
Query OK, 0 rows affected (0.00 sec)

Slave修改配置文件並重啓數據庫服務

[root@Slave data]#cat /etc/my.cnf
[mysqld]
...
rpl_semi_sync_slave_enabled        # 啓用插件功能
...

[root@Slave data]#systemctl restart mariadb

停止Slave 數據庫服務進行測試

MariaDB [(none)]> create database db3;
Query OK, 1 row affected (6.00 sec)     # 由等待時長可以看出，半同步插件已經起到效果