一、原理

mysql的主从数据同步是一个异步复制过程，需要master开启bin-log日志功能，bin-log记录了master库中的增、删、修改、更新操作的sql语句，整个过程需要开启3个线程，分别是master开启I/O线程，slave开启I/O线程和SQL线程

1、在slave服务器上执行start slave命令开启主从复制开关，主从复制开始进行，slave I/O线程会通过master创建的授权用户连接上master，并请求master从指定文件和位置之后发送bin-log日志内容

2、master接收请求后，master I/O线程更加slave发送的指定bin-log日志position点之后的内容，然后返回给slave的I/O线程；返回的信息中除了bin-log日志外，还有在master服务器记录的新的bin-log文件名及新的bin-log中的下一个指定更新位置(position)

3、slave I/O线程接收信息后，将接收的日志内容一次添加到slave端的relay-log(中继日志)文件(mysql-relay-bin.xxxxxx)的最末端，并将读取到的master端的bin-log文件名和position点记录到master.info文件中，以便下次读取时能够告知master从相应的bin-log文件名及最后一个position点开始发起请求

4、slave SQL 线程检测到relay-log中I/O线程新增加的内容有更新，会立即分析relay-log日志中的内容，将解析的sql语句按顺序在slave里执行，并记录应用中继日志的文件名及位置点在relay-log.info中，执行成功后slave库与master库数据保持一致

总结

主从复制是异步的逻辑的SQL语句级的复制

复制时，主库有一个I/O线程，从库有两个线程，I/O和SQL线程

作为复制的所有mysql节点server-id都不能相同

bin-log文件只记录对数据库有更改的sql语句(数据库内容的变更)，不记录任何查询(select，slow)语句

原理流程图如下：

主从复制条件

开启binlog功能

主库要建立账号

从库要配置master.info

start slave 开启复制功能

二、环境

master：192.168.216.52

slave:192.168.216.53

mariadb版本10.2.24

[root@web2 ~]# rpm -qa Maria*MariaDB-server-10.2.24-1.el7.centos.x86_64

MariaDB-compat-10.2.24-1.el7.centos.x86_64

MariaDB-common-10.2.24-1.el7.centos.x86_64

MariaDB-client-10.2.24-1.el7.centos.x86_64

[root@web2~]#

三、安装配置

1、添加mariadb，yum源

[root@web2 ~]# cat /etc/yum.repos.d/mariadb.repo

[mariadb]

name=MariaDB

baseurl= https://mirrors.ustc.edu.cn/mariadb/yum/10.2/centos7-amd64/

gpgkey=https://mirrors.ustc.edu.cn/mariadb/yum/RPM-GPG-KEY-MariaDB

gpgcheck=1

2、这里yum安装

两台机器都安装

yum install  mariadb-server

3、初始化mariadb，可以忽略

4、配置master

-------------------修改配置文件(红色部分关键，其他为优化)

[root@web2 my.cnf.d]# catserver.cnf

#

# Thesegroupsare read by MariaDB server.

# Use itforoptions that only the server (but not clients) should see

#

# See the examples of server my.cnf filesin /usr/share/mysql/#

# this is read by the standalone daemon and embedded servers

[server]

# this is onlyforthe mysqld standalone daemon

[mysqld]

server-id=1

log-bin=mysql-bin

#binlog-do-db=liting

#binlog-ignore-db=mysql

sync_binlog=1

binlog_checksum = none

binlog_format = mixed

port = 3306

socket = /var/lib/mysql/mysql.sock

skip-external-locking

key_buffer_size=256MB

max_allowed_packet=1MB

table_open_cache= 256sort_buffer_size=1MB

read_buffer_size=1MB

read_rnd_buffer_size=4MB

myisam_sort_buffer_size=64MB

thread_cache_size= 8query_cache_size=16MB

thread_concurrency= 8[mysqldump]

quick

max_allowed_packet=16MB

[mysql]

no-auto-rehash

[myisamchk]

key_buffer_size=128MB

sort_buffer_size=128MB

read_buffer=2MB

write_buffer=2MB

[mysqlhotcopy]

interactive-timeout

#

#* Galera-related settings

#

[galera]

# Mandatory settings

#wsrep_on=ON

#wsrep_provider=#wsrep_cluster_address=#binlog_format=row

#default_storage_engine=InnoDB

#innodb_autoinc_lock_mode=2#

# Allow server to accept connections on all interfaces.

#

#bind-address=0.0.0.0#

# Optional setting

#wsrep_slave_threads=1#innodb_flush_log_at_trx_commit=0# this is onlyforembedded server

[embedded]

# This group is only read by MariaDB servers, not by MySQL.

# If you use the same .cnffile forMySQL and MariaDB,

# you can put MariaDB-only options here

[mariadb]

# This group is only read by MariaDB-10.2servers.

# If you use the same .cnffile forMariaDB of different versions,

# use this groupfor options that older servers don't understand

[mariadb-10.2]

[root@web2 my.cnf.d]#

----------------------授权

grant replication slave,replication client on *.* to 'tongbu'@'%' identified by '123456';

----------------------查看bin-log及position点

MariaDB [test3]>show master status;+------------------+----------+--------------+------------------+

| File | Position | Binlog_Do_DB | Binlog_Ignore_DB |

+------------------+----------+--------------+------------------+

| mysql-bin.000003 | 320| | |

+------------------+----------+--------------+------------------+

1 row in set (0.00 sec)

5、配置slave

--------------------修改配置

[root@web3 my.cnf.d]# catserver.cnf

#

# Thesegroupsare read by MariaDB server.

# Use itforoptions that only the server (but not clients) should see

#

# See the examples of server my.cnf filesin /usr/share/mysql/#

# this is read by the standalone daemon and embedded servers

[server]

# this is onlyforthe mysqld standalone daemon

[mysqld]

socket= /var/lib/mysql/mysql.sock

port = 3306

skip-external-locking

key_buffer_size=256MB

max_allowed_packet=1MB

table_open_cache= 256sort_buffer_size=1MB

read_buffer_size=1MB

read_rnd_buffer_size=4MB

myisam_sort_buffer_size=64MB

thread_cache_size= 8query_cache_size=16MB

thread_concurrency= 8server-id = 2#

#* Galera-related settings

#

[galera]

# Mandatory settings

#wsrep_on=ON

#wsrep_provider=#wsrep_cluster_address=#binlog_format=row

#default_storage_engine=InnoDB

#innodb_autoinc_lock_mode=2#

# Allow server to accept connections on all interfaces.

#

#bind-address=0.0.0.0#

# Optional setting

#wsrep_slave_threads=1#innodb_flush_log_at_trx_commit=0# this is onlyforembedded server

[embedded]

# This group is only read by MariaDB servers, not by MySQL.

# If you use the same .cnffile forMySQL and MariaDB,

# you can put MariaDB-only options here

[mariadb]

# This group is only read by MariaDB-10.2servers.

# If you use the same .cnffile forMariaDB of different versions,

# use this groupfor options that older servers don't understand

[mariadb-10.2]

[root@web3 my.cnf.d]#

[root@web3 my.cnf.d]# cat mysql-clients.cnf #[mysql][mysqlcheck][mysqldump]也可以写在这个文件里，master我是都卸载server.cnf里面了

#

# Thesegroups are read by MariaDB command-line tools

# Use itforoptions that affect only one utility

#

[mysql]

no-auto-rehash

[mysql_upgrade]

[mysqladmin]

[mysqlbinlog]

[mysqlcheck]

key_buffer_size=128MB

sort_buffer_size=128MB

read_buffer=2MB

write_buffer=2MB

[mysqldump]

quick

max_allowed_packet=16MB

[mysqlimport]

[mysqlshow]

[mysqlslap]

[mysqlhotcopy]

interactive-timeout

[root@web3 my.cnf.d]#

---------------------slave进入mysql设置

slave指定master ip、用户名、密码、bin-log文件名、position(下面标记红色部分)

[root@web3 my.cnf.d]# mysql

Welcome to the MariaDB monitor. Commands end with ; or \g.

Your MariaDB connectionid is 12Server version:10.2.24-MariaDB MariaDB Server

Copyright (c)2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type'help;' or '\h' for help. Type '\c' to clearthe current input statement.

MariaDB [(none)]>change master tomaster_host='192.168.216.52',master_user='tongbu',master_password='123456',master_log_file='mysql-bin.000003',master_log_pos=320;MariaDB [(none)]> master_host='192.168.216.52',master_user='tongbu',master_password='123456',master_log_file='mysql-bin.000003',master_log_pos=320;

MariaDB [(none)]> slave start;

---------------查看状态正常状态如下：(正常状态关注标记紫色部分)

MariaDB [(none)]>show slave status\G*************************** 1. row ***************************Slave_IO_State: Waiting formaster to send event

Master_Host:192.168.216.52Master_User: tongbu

Master_Port:3306Connect_Retry:60Master_Log_File: mysql-bin.000004Read_Master_Log_Pos:593Relay_Log_File: web3-relay-bin.000006Relay_Log_Pos:828Relay_Master_Log_File: mysql-bin.000004Slave_IO_Running: Yes

Slave_SQL_Running: Yes

Replicate_Do_DB:

Replicate_Ignore_DB:

Replicate_Do_Table:

Replicate_Ignore_Table:

Replicate_Wild_Do_Table:

Replicate_Wild_Ignore_Table:

Last_Errno:0Last_Error:

Skip_Counter:0Exec_Master_Log_Pos:593Relay_Log_Space:1136Until_Condition: None

Until_Log_File:

Until_Log_Pos:0Master_SSL_Allowed: No

Master_SSL_CA_File:

Master_SSL_CA_Path:

Master_SSL_Cert:

Master_SSL_Cipher:

Master_SSL_Key:

Seconds_Behind_Master:0Master_SSL_Verify_Server_Cert: No

Last_IO_Errno:0Last_IO_Error:

Last_SQL_Errno:0Last_SQL_Error:

Replicate_Ignore_Server_Ids:

Master_Server_Id:1Master_SSL_Crl:

Master_SSL_Crlpath:

Using_Gtid: No

Gtid_IO_Pos:

Replicate_Do_Domain_Ids:

Replicate_Ignore_Domain_Ids:

Parallel_Mode: conservative

SQL_Delay:0SQL_Remaining_Delay: NULL

Slave_SQL_Running_State: Slave has read all relay log; waitingfor the slave I/O thread to update it1 row in set (0.00mysql主从同步(4)-Slave延迟状态监控

#  1)Slave_IO_Running：该参数可作为io_thread的监控项，Yes表示io_thread的和主库连接正常并能实施复制工作，No则说明与主库通讯异常，多数情况是由主从间网络引起的问题；

2)Slave_SQL_Running：该参数代表sql_thread是否正常，YES表示正常，NO表示执行失败，具体就是语句是否执行通过，常会遇到主键重复或是某个表不存在。

3)Seconds_Behind_Master：是通过比较sql_thread执行的event的timestamp和io_thread复制好的event的timestamp(简写为ts)进行比较，而得到的这么一个差值；

NULL—表示io_thread或是sql_thread有任何一个发生故障，也就是该线程的Running状态是No，而非Yes。

0 — 该值为零，是我们极为渴望看到的情况，表示主从复制良好，可以认为lag不存在。

正值 — 表示主从已经出现延时，数字越大表示从库落后主库越多。

负值 — 几乎很少见，我只是听一些资深的DBA说见过，其实，这是一个BUG值，该参数是不支持负值的，也就是不应该出现。

6、测试，master创建一个test3的库及t1的表

[root@web2 my.cnf.d]#mysql -uroot -p

Enter password:

Welcome to the MariaDB monitor. Commands end with ; or \g.

Your MariaDB connectionid is 11Server version:10.2.24-MariaDB-log MariaDB Server

Copyright (c)2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type'help;' or '\h' for help. Type '\c' to clearthe current input statement.MariaDB [(none)]>MariaDB [(none)]>create database test3;

Query OK,1 row affected (0.00sec)

MariaDB [(none)]>use test3;

Database changed

MariaDB [test3]> create table t1(id varchar(20),name varchar(20));

Query OK,0 rows affected (0.02sec)

MariaDB [test3]>show tables;+-----------------+

| Tables_in_test3 |

+-----------------+

| t1 |

+-----------------+

1 row in set (0.00sec)

MariaDB [test3]>

---------------slave查看已经同步过来了

MariaDB [(none)]>show databases;+--------------------+

| Database |

+--------------------+

| information_schema |

| mysql |

| performance_schema |

| test |

| test3 |

+--------------------+

5 rows in set (0.00sec)

MariaDB [(none)]>