Mariadb/Mysql 主从复制（1）

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.-.el7.centos.x86_64
MariaDB-compat-10.2.-.el7.centos.x86_64
MariaDB-common-10.2.-.el7.centos.x86_64
MariaDB-client-10.2.-.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=

　　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

　　　　参考：https://www.cnblogs.com/zhangxingeng/p/10882845.html

　　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]# cat server.cnf
#
# These groups are read by MariaDB server.
# Use it for options that only the server (but not clients) should see
#
# See the examples of server my.cnf files in /usr/share/mysql/
#

# this is read by the standalone daemon and embedded servers
[server]

# this is only for the 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        =
sort_buffer_size        = 1MB
read_buffer_size        = 1MB
read_rnd_buffer_size    = 4MB
myisam_sort_buffer_size = 64MB
thread_cache_size       =
query_cache_size        = 16MB
thread_concurrency      = 

[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=
#
# Allow server to accept connections on all interfaces.
#
#bind-address=0.0.0.0
#
# Optional setting
#wsrep_slave_threads=
#innodb_flush_log_at_trx_commit=

# this is only for embedded server
[embedded]

# This group is only read by MariaDB servers, not by MySQL.
# If you use the same .cnf file for MySQL and MariaDB,
# you can put MariaDB-only options here
[mariadb]

# This group is only read by MariaDB-10.2 servers.
# If you use the same .cnf file for MariaDB of different versions,
# use this group for 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 '';

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

MariaDB [test3]> show master status;
+------------------+----------+--------------+------------------+
| File             | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+------------------+----------+--------------+------------------+
| mysql-bin. |      |              |                  |
+------------------+----------+--------------+------------------+
 row in set (0.00 sec)

　　5、配置slave

--------------------修改配置

[root@web3 my.cnf.d]# cat server.cnf
#
# These groups are read by MariaDB server.
# Use it for options that only the server (but not clients) should see
#
# See the examples of server my.cnf files in /usr/share/mysql/
#

# this is read by the standalone daemon and embedded servers
[server]

# this is only for the 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        =
sort_buffer_size        = 1MB
read_buffer_size        = 1MB
read_rnd_buffer_size    = 4MB
myisam_sort_buffer_size = 64MB
thread_cache_size       =
query_cache_size        = 16MB
thread_concurrency      = 
server-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=
#
# Allow server to accept connections on all interfaces.
#
#bind-address=0.0.0.0
#
# Optional setting
#wsrep_slave_threads=
#innodb_flush_log_at_trx_commit=

# this is only for embedded server
[embedded]

# This group is only read by MariaDB servers, not by MySQL.
# If you use the same .cnf file for MySQL and MariaDB,
# you can put MariaDB-only options here
[mariadb]

# This group is only read by MariaDB-10.2 servers.
# If you use the same .cnf file for MariaDB of different versions,
# use this group for 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
#
# These groups are read by MariaDB command-line tools
# Use it for options 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 connection id is
Server version: 10.2.-MariaDB MariaDB Server

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

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

MariaDB [(none)]> change master to master_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
*************************** . row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 192.168.216.52
Master_User: tongbu
Master_Port:
Connect_Retry:
Master_Log_File: mysql-bin.
Read_Master_Log_Pos:
Relay_Log_File: web3-relay-bin.
Relay_Log_Pos:
Relay_Master_Log_File: mysql-bin.
Slave_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:
Last_Error:
Skip_Counter:
Exec_Master_Log_Pos:
Relay_Log_Space:
Until_Condition: None
Until_Log_File:
Until_Log_Pos:
Master_SSL_Allowed: No
Master_SSL_CA_File:
Master_SSL_CA_Path:
Master_SSL_Cert:
Master_SSL_Cipher:
Master_SSL_Key:
Seconds_Behind_Master:
Master_SSL_Verify_Server_Cert: No
Last_IO_Errno:
Last_IO_Error:
Last_SQL_Errno:
Last_SQL_Error:
Replicate_Ignore_Server_Ids:
Master_Server_Id:
Master_SSL_Crl:
Master_SSL_Crlpath:
Using_Gtid: No
Gtid_IO_Pos:
Replicate_Do_Domain_Ids:
Replicate_Ignore_Domain_Ids:
Parallel_Mode: conservative
SQL_Delay:
SQL_Remaining_Delay: NULL
Slave_SQL_Running_State: Slave has read all relay log; waiting for the slave I/O thread to update it
 row in set (0.00 sec)

需要关注如下几点
引用：https://www.cnblogs.com/kevingrace/p/5685511.html mysql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 connection id is
Server version: 10.2.-MariaDB-log MariaDB Server

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

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

MariaDB [(none)]>
MariaDB [(none)]> create database test3;
Query OK,  row affected (0.00 sec)

MariaDB [(none)]> use test3;
Database changed
MariaDB [test3]> create table t1(id varchar(),name varchar());
Query OK,  rows affected (0.02 sec)

MariaDB [test3]> show tables;
+-----------------+
| Tables_in_test3 |
+-----------------+
| t1              |
+-----------------+
 row in set (0.00 sec)

MariaDB [test3]> 

　　

---------------slave查看已经同步过来了

MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| test               |
| test3              |
+--------------------+
 rows in set (0.00 sec)

MariaDB [(none)]> 

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