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HomeDatabaseMysql TutorialMySQL 复制简要描述及示例

主从复制技术在MySQL中被广泛使用,主要用于同步一台服务器上的数据至多台从服务器,可以用于实现负载均衡,高可用和故障切换,以

主从复制技术在MySQL中被广泛使用,,主要用于同步一台服务器上的数据至多台从服务器,可以用于实现负载均衡,高可用和故障切换,以及提供备份等等。MySQL支持多种不同的复制技术,诸如单向,半同步异步复制等以及不同级别的复制,诸如数据库级别,表级,跨库同步等等。本文简要描述了一个基本的主从复制并给出示例。

1、复制的基本原理(步骤)

a、在主库上把数据更改记录的二进制日志(binary log)

b、从库上的I/O线程连接到主库并请求发送其二进制日志文件(主库上的binlog dump线程将二进制日志内容发送到从库)

c、从库上的I/O线程读取主服务发送的二进制内容并将其拷贝到中继日志

d、从库上的SQL线程读取中继日志并执行日志中包含的更新

2、为配置文件添加复制项

# 本文的演示基于同一服务器上的多实例环境,其中3406端口用作主库,而3506用作从库。
# 关于多实例的部署可参考:
# MySQL多实例配置 
# 3406与3506为都为新装且含缺省库等,所以本文演示中未涉及先迁移主库数据到备库步骤
a、主库上的配置文件
# more my3406.cnf
[mysqld]
socket = /tmp/mysql3406.sock
port = 3406
pid-file = /data/inst3406/data3406/my3406.pid
user = mysql
log-error=/data/inst3406/data3406/inst3406.err
datadir=/data/inst3406/data3406
basedir=/app/soft/mysql5

#### for master items ####
server-id=3406
log_bin=/data/inst3406/log/bin/inst3406bin
innodb_flush_log_at_trx_commit=1
sync_binlog=1

b、从库上的配置文件
# more my3506.cnf
[mysqld]
socket = /tmp/mysql3506.sock      # Author : Leshami
port = 3506                      # Blog  :
pid-file
= /data/inst3506/data3506/my3506.pid
user = mysql
log-error=/data/inst3506/data3506/inst3506.err
datadir=/data/inst3506/data3506
basedir=/app/soft/mysql5

#### for slave items ####
server-id=3506
relay_log=/data/inst3506/log/relay/relay-bin
read_only=1

3、创建复制账号

#启动端口为3406的实例并添加账户
[mysql@app ~]$ mysqld_safe --defaults-file=/data/inst3406/data3406/my3406.cnf &
[mysql@app ~]$ mysql -P3406    #登陆到3406

master@localhost[(none)]> show variables like 'server_id';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| server_id    | 3406  |
+---------------+-------+

#创建用于复制的账户
master@localhost[(none)]> grant replication slave,replication client on *.*
    -> to repl@'192.168.1.177' identified by 'repl';

#初始化主库日志文件,生成环境慎用reset
master@localhost[(none)]> reset master;
Query OK, 0 rows affected (0.01 sec)

#查看主库的状态,日志初始化至000001,
master@localhost[(none)]> show master status,Position为120
+--------------------+----------+--------------+------------------+-------------------+
| File              | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+--------------------+----------+--------------+------------------+-------------------+
| inst3406bin.000001 |      120 |              |                  |                  |
+--------------------+----------+--------------+------------------+-------------------+

4、配置主从同步

#启动端口为3506的实例
[mysql@app ~]$ mysqld_safe --defaults-file=/data/inst3506/data3506/my3506.cnf &

[mysql@app ~]$ msyql -P3506

slave@localhost[(none)]> show variables like 'server_id';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| server_id    | 3506  |
+---------------+-------+
1 row in set (0.00 sec)

#为从库添加指向主库的相关配置信息,该命令会生成及修改备库上的master.info及relay-log.info文件
slave@localhost[(none)]> CHANGE MASTER TO MASTER_HOST='192.168.1.177',
    -> MASTER_USER='repl',
    -> MASTER_PASSWORD='repl',
    -> MASTER_PORT=3406,
    -> MASTER_LOG_FILE='inst3406bin.000001',
    -> MASTER_LOG_POS=0;
Query OK, 0 rows affected, 2 warnings (0.04 sec)

#出现了2个warnings,查看一下
slave@localhost[(none)]> show warnings \G
*************************** 1. row ***************************
  Level: Note
  Code: 1759
Message: Sending passwords in plain text without SSL/TLS is extremely insecure.
*************************** 2. row ***************************
  Level: Note
  Code: 1760
Message: Storing MySQL user name or password information in the master.info repository is not secure and is therefore not recommended.
Please see the MySQL Manual for more about this issue and possible alternatives.
2 rows in set (0.00 sec)

#此时查看从库的状态信息
slave@localhost[(none)]> show slave status \G
*************************** 1. row ***************************
              Slave_IO_State:
                  Master_Host: 192.168.1.177
                  Master_User: repl
                  Master_Port: 3406
                Connect_Retry: 60
              Master_Log_File: inst3406bin.000001
          Read_Master_Log_Pos: 4
              Relay_Log_File: relay-bin.000001
                Relay_Log_Pos: 4
        Relay_Master_Log_File: inst3406bin.000001
            Slave_IO_Running: No      #IO线程没有运行
            Slave_SQL_Running: No      #SQL线程没有运行
                    ......................
            Master_Info_File: /data/inst3506/data3506/master.info

slave@localhost[(none)]> start slave;  #启动slave
Query OK, 0 rows affected (0.01 sec)

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