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./mariadb/yum/10.2/centos7-amd64/
gpgkey=https://mirrors./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 f.d]# f
#
# Thesegroupsare read by MariaDB server.
# Use itforoptions that only the server (but not clients) should see
#
# See the examples of server f 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 f.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 f.d]# f
#
# Thesegroupsare read by MariaDB server.
# Use itforoptions that only the server (but not clients) should see
#
# See the examples of server f 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 f.d]#
[root@web3 f.d]# cat mysql-f #[mysql][mysqlcheck][mysqldump]也可以写在这个文件里，master我是都卸载f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 f.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 f.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, , 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 f.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, , 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)]>
