1、主从复制架构和原理
1.1服务性能扩展方式 Scale Up，向上扩展，垂直扩展
Scale Out，向外扩展，横向扩展
1.2MySQL的扩展 读写分离
复制：每个节点都有相同的数据集，向外扩展，基于二进制日志的单向复制
1.3复制的功用
@数据分布 @负载均衡读 @备份 @高可用和故障切换 @MySQL升级测试
1.4主从复制架构
一主一从复制架构
一主多从复制架构
1.5主从复制原理
主从复制相关线程
主节点：
dump Thread：为每个Slave的I/O Thread启动一个dump线程，用于向其发送binary log events
从节点：
I/O Thread：向Master请求二进制日志事件，并保存于中继日志中
SQL Thread：从中继日志中读取日志事件，在本地完成重放
跟复制功能相关的文件：
master.info：用于保存slave连接至master时的相关信息，例如账号、密码、服务器地址等
relay-log.info：保存在当前slave节点上已经复制的当前二进制日志和本地relay log日志的对应关系
mariadb-relay-bin.00000#: 中继日志,保存从主节点复制过来的二进制日志,本质就是二进制日志
范例: 中继日志
[root@slave ~]#file /var/lib/mysql/mariadb-relay-bin.000001 /var/lib/mysql/mariadb-relay-bin.000001: MySQL replication log, server id 18 MySQL V5+, server version 10.3.17-MariaDB-log [root@slave ~]#mysqlbinlog /var/lib/mysql/mariadb-relay-bin.000001|head /*!50530 SET @@SESSION.PSEUDO_SLAVE_MODE=1*/; /*!40019 SET @@session.max_insert_delayed_threads=0*/; /*!50003 SET @OLD_COMPLETION_TYPE=@@COMPLETION_TYPE,COMPLETION_TYPE=0*/; DELIMITER /*!*/; # at 4 #200615 17:58:48 server id 18 end_log_pos 256 CRC32 0x7bd00c79 Start: binlog v 4, server v 10.3.17-MariaDB-log created 200615 17:58:48 BINLOG ' WEbnXg8cAAAA/AAAAAABAAAAAAQAMTAuMy4xNy1NYXJpYURCLWxvZwAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAEzgNAAgAEgAEBAQEEgAA5AAEGggAAAAICAgCAAAACgoKAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
1.6主从复制特点
@异步复制 @主从数据不一致比较常见
1.7各种复杂架构
@一master/一slave @一主一从 @从服务器还可以再有从服务器 @Master/Master
@一从多主:适用于多个不同数据库 @环状复制
2、实现主从复制配置
参考官网
https://mariadb.com/kb/en/library/setting-up-replication/
https://dev.mysql.com/doc/refman/5.5/en/replication-configuration.html
主节点配置：
(1) 启用二进制日志
[root@centos8 ~]# vim /etc/my.cnf.d/mariadb-server.cnf
[mysqld]
log_bin
(2) 为当前节点设置一个全局惟一的ID号
[mysqld] server-id= #设置的IP最后一位 log-basename=master #可选项，设置datadir中日志名称，确保不依赖主机名 文件前缀
server-id的取值范围
1 to 4294967295 (>= MariaDB 10.2.2)，默认值为1
0 to 4294967295 (<= MariaDB 10.2.1)，默认值为0，如果从节点为0，所有master都将拒绝此slave的连接
(3) 创建有复制权限的用户账号
GRANT REPLICATION SLAVE ON *.* TO 'repluser'@'HOST' IDENTIFIED BY 'replpass';
主机IP 密码
(4) 查看从二进制日志的文件和位置开始进行复制
MariaDB [(none)]>SHOW MASTER LOG;
从节点配置：
(1) 启动中继日志
[mysqld] server_id=# #为当前节点设置一个全局惟的ID号 log-bin #启用二进制 read_only=ON #设置数据库只读，针对supper user无效 relay_log=relay-log #relay log的文件路径，默认值hostname-relay-bin relay_log_index=relay-log.index #默认值hostname-relay-bin.index
(2) 使用有复制权限的用户账号连接至主服务器，并启动复制线程
CHANGE MASTER TO MASTER_HOST='masterhost', MASTER_USER='repluser', MASTER_PASSWORD='replpass', MASTER_LOG_FILE='mariadb-bin.xxxxxx', MASTER_LOG_POS=#; START SLAVE [IO_THREAD|SQL_THREAD]; SHOW SLAVE STATUS;
范例：
#主节点 [root@master ~]#vim /etc/my.cnf.d/mariadb-server.cnf [mysqld] server-id=134 log-bin [root@master ~]#systemctl restart mariadb [root@master ~]#mysql MariaDB [(none)]> grant replication slave on *.* to repluser@'10.0.0.%' identified by '123456'; #查看二进制文件和位置 MariaDB [(none)]> show master logs; +--------------------+-----------+ | Log_name | File_size | +--------------------+-----------+ | mariadb-bin.000001 | 28052 |
| mariadb-bin.000002 | 545 |
+--------------------+-----------+
2 rows in set (0.001 sec)
#从节点
[root@slave ~]#vim /etc/my.cnf.d/mariadb-server.cnf
[mysqld]
server-id=135
[root@slave ~]#systemctl restart mariadb
[root@slave1 ~]#mysql MariaDB [(none)]> help change master to
MariaDB [(none)]>CHANGE MASTER TO MASTER_HOST='10.0.0.134',
MASTER_USER='repluser',
MASTER_PASSWORD='123456',
MASTER_PORT=3306,
MASTER_LOG_FILE='mariadb-bin.000002',
MASTER_LOG_POS=545;
MariaDB [(none)]> start slave;
Query OK, 0 rows affected, 1 warning (0.000 sec)
MariaDB [(none)]> show slave statusG
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 10.0.0.134
Master_User: repluser
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mariadb-bin.000002
Read_Master_Log_Pos: 26987890
Relay_Log_File: mariadb-relay-bin.000002
Relay_Log_Pos: 26987902
Relay_Master_Log_File: mariadb-bin.000002
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: 0
Last_Error:
Skip_Counter: 0
Exec_Master_Log_Pos: 26987890
Relay_Log_Space: 26988213
Until_Condition: None
Until_Log_File:
Until_Log_Pos: 0
Master_SSL_Allowed: No
Master_SSL_CA_File:
Master_SSL_CA_Path:
Master_SSL_Cert:
Master_SSL_Cipher:
Master_SSL_Key:
Seconds_Behind_Master: 0 #复制的延迟时间
Master_SSL_Verify_Server_Cert: No
Last_IO_Errno: 0
Last_IO_Error:
Last_SQL_Errno: 0
Last_SQL_Error:
Replicate_Ignore_Server_Ids:
Master_Server_Id: 8
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: 0
SQL_Remaining_Delay: NULL
Slave_SQL_Running_State: Slave has read all relay log; waiting for the
slave I/O thread to update it
Slave_DDL_Groups: 34
Slave_Non_Transactional_Groups: 0
Slave_Transactional_Groups: 100006
1 row in set (0.000 sec)
范例：主服务器非新建时,主服务器运行一段时间后，新增从节点服务器
如果主节点已经运行了一段时间，且有大量数据时，如何配置并启动slave节点
@通过备份恢复数据至从服务器
@复制起始位置为备份时，二进制日志文件及其POS
#在主服务器完全备份 [root@master ~]#mysqldump -A -F --single-transaction --master-data=1 > /backup/fullbackup_`date +%F_%T`.sql [root@master ~]#ll /backup/ total 2988 -rw-r--r-- 1 root root 3055918 Nov 27 17:41 fullbackup_2020-10-13_09:33:07.sql [root@master ~]#scp /backup/fullbackup_2020-10-13_09:33:07.sql 10.0.0.135:/data/
#建议优化主和从节点服务器的性能
MariaDB [hellodb]> set global innodb_flush_log_at_trx_commit=2
MariaDB [hellodb]> set global sync_binlog=0
MariaDB [hellodb]> set global innodb_flush_log_at_trx_commit=2;
Query OK, 0 rows affected (0.001 sec)
MariaDB [hellodb]> show variables like 'sync_binlog';
+---------------------+-------+
| Variable_name | Value |
+---------------------+-------+
| sync_binlog | 0 |
|---------------------+-------+
5 rows in set (0.001 sec)
#将完全备份还原到新的从节点
[root@slave ~]#dnf -y install mariadb-server
[root@slave ~]#vim /etc/my.cnf.d/mariadb-server.cnf
[mysqld]
server-id=135
read-only [root@slave ~]#systemctl restart mariadb
#配置从节点，从完全备份的位置之后开始复制
[root@slave ~]#grep '^CHANGE MASTER' /data/fullbackup_2020-10-13_09:33:07.sql
CHANGE MASTER TO MASTER_LOG_FILE='mariadb-bin.000003', MASTER_LOG_POS=389;
[root@slave ~]#vim /data/fullbackup_2020-10-13_09:33:07.sql
CHANGE MASTER TO
MASTER_HOST='10.0.0.134',
MASTER_USER='repluser',
MASTER_PASSWORD='123456',
MASTER_PORT=3306,
MASTER_LOG_FILE='mariadb-bin.000003',
MASTER_LOG_POS=389;
[root@slave ~]#mysql < /data/fullbackup_2020-10-13_09:33:07.sql
[root@slave ~]#mysql
MariaDB [(none)]> show slave statusG;
*************************** 1. row ***************************
Slave_IO_State:
Master_Host: 10.0.0.134
Master_User: repluser
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mariadb-bin.000003
Read_Master_Log_Pos: 389
Relay_Log_File: mariadb-relay-bin.000001
Relay_Log_Pos: 4
Relay_Master_Log_File: mariadb-bin.000003
Slave_IO_Running: No
Slave_SQL_Running: No .
.
.省略
3、主从复制相关
3.1限制服务器为只读
read_only=ON
#注意：此限制对拥有SUPER权限的用户均无效
注意：以下命令会阻止所有用户, 包括主服务器复制的更新
FLUSH TABLES WITH READ LOCK;
3.2在从节点清除信息
注意：一下都需要先stop slave
RESET SLAVE #从服务器清除master.info ，relay-log.info, relay log ，开始新的relay log RESET SLAVE ALL #清除所有从服务器上设置的主服务器同步信息，如HOST，PORT, USER和PASSWORD 等
3.3复制错误解决方法
可以在从服务器忽略几个主服务器的复制事件，此为global变量，或指定跳过事件的ID
注意: Centos 8.1以上版本上主从节点同时建同名的库和表不会冲突，建主键记录会产生冲突
#系统变量，指定跳过复制事件的个数 SET GLOBAL sql_slave_skip_counter = N #服务器选项，只读系统变量，指定跳过事件的ID [mysqld] slave_skip_errors=1007|ALL
范例：复制冲突的解决
#CentOS7上Mariadb5.5 在slave创建库和表,再在master上创建同名的库和表,会出现复制冲突,而在
CentOS8上的Mariadb10.3上不会冲突 #如果添加相同的主键记录都会冲突 MariaDB [(none)]> show slave statusG *************************** 1. row *************************** Slave_IO_State: Waiting for master to send event Master_Host: 10.0.0.134 Master_User: repluser Master_Port: 3306 Connect_Retry: 60 Master_Log_File: mariadb-bin.000002 Read_Master_Log_Pos: 26988271 Relay_Log_File: mariadb-relay-bin.000003 Relay_Log_Pos: 557 Relay_Master_Log_File: mariadb-bin.000002 Slave_IO_Running: Yes Slave_SQL_Running: No Replicate_Do_DB: Replicate_Ignore_DB:
Replicate_Do_Table:
Replicate_Ignore_Table:
Replicate_Wild_Do_Table:
Replicate_Wild_Ignore_Table:
Last_Errno: 1007
Last_Error: Error 'Can't create database 'db4'; database
exists' on query. Default database: 'db4'. Query: 'create database db4'
Skip_Counter: 0
Exec_Master_Log_Pos: 26988144
Relay_Log_Space: 26988895
Until_Condition: None
Until_Log_File:
Until_Log_Pos: 0
Master_SSL_Allowed: No
Master_SSL_CA_File:
Master_SSL_CA_Path:
Master_SSL_Cert:
Master_SSL_Cipher:
Master_SSL_Key:
Seconds_Behind_Master: NULL
Master_SSL_Verify_Server_Cert: No
Last_IO_Errno: 0
Last_IO_Error:
Last_SQL_Errno: 1007 #错误编码
Last_SQL_Error: Error 'Can't create database 'db4'; database
exists' on query. Default database: 'db4'. Query: 'create database db4'
Replicate_Ignore_Server_Ids:
Master_Server_Id: 8
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: 0
SQL_Remaining_Delay: NULL
Slave_SQL_Running_State:
Slave_DDL_Groups: 37
Slave_Non_Transactional_Groups: 0
Slave_Transactional_Groups: 100006
1 row in set (0.000 sec)
#方法1
MariaDB [(none)]> stop slave;
MariaDB [(none)]> set global sql_slave_skip_counter=1;
MariaDB [(none)]> start slave;
#方法2
[root@slave1 ~]#vim /etc/my.cnf.d/mariadb-server.cnf
[mysqld]
slave_skip_errors=1007|ALL
[root@slave1 ~]#systemctl restart mariadb
1.4START SLAVE 语句，指定执到特定的点
START SLAVE [thread_types] START SLAVE [SQL_THREAD] UNTIL MASTER_LOG_FILE = 'log_name', MASTER_LOG_POS = log_pos START SLAVE [SQL_THREAD] UNTIL RELAY_LOG_FILE = 'log_name', RELAY_LOG_POS = log_pos thread_types: [thread_type [, thread_type] ... ] thread_type: IO_THREAD | SQL_THREAD
1.5 保证主从复制的事务安全
参看https://mariadb.com/kb/en/library/server-system-variables/
在master节点启用参数：
sync_binlog=1 每次写后立即同步二进制日志到磁盘，性能差 #如果用到的为InnoDB存储引擎： innodb_flush_log_at_trx_commit=1 #每次事务提交立即同步日志写磁盘 innodb_support_xa=ON #分布式事务MariaDB10.3.0废除 sync_master_info=# #次事件后master.info同步到磁盘
在slave节点启用服务器选项：
skip-slave-start=ON #不自动启动slave
在slave节点启用参数：
sync_relay_log=# #次写后同步relay log到磁盘
sync_relay_log_info=# #次事务后同步relay-log.info到磁盘
3.6案例：当master服务器宕机，提升一个slave成为新的master
#找到哪个从节点的数据库是最新，让它成为新master [root@centos8 ~]#cat /var/lib/mysql/relay-log.info 5 ./mariadb-relay-bin.000002 1180 mysql-bin.000002 996 0
#新master修改配置文件，关闭read-only配置
[root@slave1 ~]#vim /etc/my.cnf.d/mariadb-server.cnf
[mysqld]
server-id=135
read-only=OFF
log-bin=/data/mysql/logbin/mysql-bin
#清除旧的master复制信息
MariaDB [hellodb]>set global read_only=off;
MariaDB [hellodb]>stop slave;
MariaDB [hellodb]>reset slave all；
#在新master上完全备份
[root@slave1 ~]#mysqldump -A --single-transaction --master-data=1 -F >backup.sql
[root@slave1 ~]#scp backup.sql 10.0.0.136:
#分析旧的master二进制日志，将未同步到新master的二进制文件导出，恢复到新master，尽可能恢复数据
#其他所有slave重新还原数据库，指向新的master
[root@slave2 ~]#vim backup.sql
CHANGE MASTER TO
MASTER_HOST='10.0.0.135',
MASTER_USER='repluser',
MASTER_PASSWORD='123456',
MASTER_PORT=3306,
MASTER_LOG_FILE='mysql-bin.000002',MASTER_LOG_POS=371;
MariaDB [hellodb]>stop slave;
MariaDB [hellodb]>reset slave all;
MariaDB [hellodb]>set sql_log_bin=off;
MariaDB [hellodb]>source backup.sql;
MariaDB [hellodb]>set sql_log_bin=on;
MariaDB [hellodb]>start slave;