MySQL主从复制
主从复制原理：
mysql主从同步其实是一个异步复制的过程,要实现复制首先在master上开启bin-log日志功能。整个过程需要开启3个线程, 分别是master开启IO线程,slave开启IO线程和SQL线程. (1) 在slave服务器执行start slave,服务器的IO线程的请求后,master服务器的IO线程根据slave服务器发送指定的bin-log日志之后得内容, 然后返回给slave端的IO线程;(返回的信息中除了bin-log日志内容外,还有本地返回日志内容后再master服务器的新的binlog文件 及在binlog中的下一个指定更新位置) (2) slave的IO线程接收到信息后,将接受到的日志一次添加到slave端的relay-log文件的最末端,并将读取到的master端的bin-log的文件名 和位置记录到master-info文件中,以便在下一次读取的时候能够清楚的告诉master, "我需要从某个bin-log的哪个位置开始往后的日志内容,请发给我;" (3) slave的SQL线程检测到relay-log中新增加了内容后,会马上解析relay-log的内容成为master端真实执行 时间的那些可执行的内容,并且重新回放.
安装其实很简单,主要得理解原理。
环境：mariadb-5.5.44源码
mysql 主:192.168.155.12
mysql 从:192.168.155.13
实现mysql主从同步,以下是mysql主从操作步骤、（源码环境以及按照好）
mysql安装目录 /usr/local/mysql mysql数据目录/mydata/data mysql配置文件/etc/my.cnf
在mysql主上，操作如下：
# vim /etc/my.cnf
[client] port = 3306 socket = /tmp/mysql.sock [mysqld] port = 3306 socket = /tmp/mysql.sock skip-external-locking key_buffer_size = 256M max_allowed_packet = 1M table_open_cache = 256 sort_buffer_size = 1M read_buffer_size = 1M read_rnd_buffer_size = 4M myisam_sort_buffer_size = 64M thread_cache_size = 8 query_cache_size= 16M thread_concurrency = 8 datadir = /mydata/data ##mysql数据目录 innodb_file_per_table = on ##InnoDB为独立表空间模式，每一个数据库，每一个表都会生成一个数据空间. skip_name_resolve = on ##关闭dns反解 log-bin=mysql-bin ##binlog文件名字,文件默认存放于数据目录中，即：/mydata/data binlog_format=row ##binlog格式为基于行的复制 server-id = 1 ##master必须指定唯一server_id sync_binlog = 1 ##及时写入bin-log日志 log_error= /mydata/data/error.log ##mysql错误日志 [mysqld-safe] pid-file=/mydata/data/mysqld.pid ##mysql的pid存放路径 replicate-do-db =all ##同步全部的数据库，如果只同步某一个数据库，改成数据库名称就可以. [mysqldump] quick max_allowed_packet = 16M [mysql] no-auto-rehash [myisamchk] key_buffer_size = 128M sort_buffer_size = 128M read_buffer = 2M write_buffer = 2M [mysqlhotcopy] interactive-timeout
# /etc/init.d/mysqld restart # mysql MariaDB [(none)]> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | mysql | | performance_schema | | test | +--------------------+ 4 rows in set (0.00 sec) MariaDB [(none)]> GRANT REPLICATION SLAVE,REPLICATION CLIENT ON *.* TO 'repluser'@'192.168.155.13' IDENTIFIED BY 'replpass'; Query OK, 0 rows affected (0.00 sec) MariaDB [(none)]> flush privileges; Query OK, 0 rows affected (0.01 sec) MariaDB [(none)]> show master status \G *************************** 1. row *************************** File: mysql-bin.000004 Position: 500 Binlog_Do_DB: Binlog_Ignore_DB: 1 row in set (0.00 sec)
在mysql从上，操作如下：
# vim /etc/my.cnf [client] port = 3306 socket = /tmp/mysql.sock [mysqld] port = 3306 socket = /tmp/mysql.sock skip-external-locking key_buffer_size = 256M max_allowed_packet = 1M table_open_cache = 256 sort_buffer_size = 1M read_buffer_size = 1M read_rnd_buffer_size = 4M myisam_sort_buffer_size = 64M thread_cache_size = 8 query_cache_size= 16M thread_concurrency = 8 datadir = /mydata/data innodb_file_per_table = on skip_name_resolve = on relay-log=relay-log ##开启中继日志，中继日志名为relay-log，默认存放于数据目录/mydata/data下 relay-log-index=relay-log.index ##定义relay_log的位置和名称 binlog_format=row server-id = 2 ##slave必须指定唯一server_id sync_binlog = 1 log_error= /mydata/data/error.log [mysqld-safe] pid-file=/mydata/data/mysqld.pid replicate-do-db =all [mysqldump] quick max_allowed_packet = 16M [mysql] no-auto-rehash [myisamchk] key_buffer_size = 128M sort_buffer_size = 128M read_buffer = 2M write_buffer = 2M [mysqlhotcopy] interactive-timeout
# /etc/init.d/mysqld restart # mysql MariaDB [(none)]> CHANGE MASTER TO MASTER_HOST='192.168.155.12',MASTER_USER='repluser',MASTER_PASSWORD='replpass',MASTER_LOG_FILE='mysql-bin.000004',MASTER_LOG_POS=500; Query OK, 0 rows affected (0.04 sec) MariaDB [(none)]> show slave status \G *************************** 1. row *************************** Slave_IO_State: Master_Host: 192.168.155.12 Master_User: repluser Master_Port: 3306 Connect_Retry: 60 Master_Log_File: mysql-bin.000004 Read_Master_Log_Pos: 500 Relay_Log_File: relay-log.000001 Relay_Log_Pos: 4 Relay_Master_Log_File: mysql-bin.000004 Slave_IO_Running: No ##没开启IO线程 Slave_SQL_Running: No ##没开启SQL线程 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: 500 Relay_Log_Space: 245 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: 0 Last_SQL_Error: Replicate_Ignore_Server_Ids: Master_Server_Id: 0 1 row in set (0.00 sec) MariaDB [(none)]> start slave ; Query OK, 0 rows affected (0.01 sec) MariaDB [(none)]> show slave status \G *************************** 1. row *************************** Slave_IO_State: Connecting to master Master_Host: 192.168.155.12 Master_User: repluser Master_Port: 3306 Connect_Retry: 60 Master_Log_File: mysql-bin.000004 Read_Master_Log_Pos: 500 Relay_Log_File: relay-log.000001 Relay_Log_Pos: 4 Relay_Master_Log_File: mysql-bin.000004 Slave_IO_Running: Connecting 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: 500 Relay_Log_Space: 245 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: 2003 Last_IO_Error: error connecting to master 'repluser@192.168.155.12:3306' - retry-time: 60 retries: 86400 message: Can't connect to MySQL server on '192.168.155.12' (113) Last_SQL_Errno: 0 Last_SQL_Error: Replicate_Ignore_Server_Ids: Master_Server_Id: 0 1 row in set (0.00 sec) 问题：为什么开启IO/SQL线程还是不能同步; 解决思路：检查下iptables是否关闭，ip:port是否通了 # /etc/init.d/iptables stop iptables: Setting chains to policy ACCEPT: filter [ OK ] iptables: Flushing firewall rules: [ OK ] iptables: Unloading modules: [ OK ] 关闭防火墙之后，进入mysql查看下slave状态; # mysql MariaDB [(none)]> show slave status \G *************************** 1. row *************************** Slave_IO_State: Waiting for master to send event Master_Host: 192.168.155.12 Master_User: repluser Master_Port: 3306 Connect_Retry: 60 Master_Log_File: mysql-bin.000004 Read_Master_Log_Pos: 500 Relay_Log_File: relay-log.000002 Relay_Log_Pos: 529 Relay_Master_Log_File: mysql-bin.000004 Slave_IO_Running: Yes ##代表已经开启IO线程 Slave_SQL_Running: Yes ##代表已经开启SQL线程 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: 500 Relay_Log_Space: 817 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 ##这个可以看到主从同步是否有延迟，然后延迟秒数 Master_SSL_Verify_Server_Cert: No Last_IO_Errno: 0 Last_IO_Error: ##是否会出现问题以及原因 Last_SQL_Errno: 0 Last_SQL_Error: Replicate_Ignore_Server_Ids: Master_Server_Id: 1 1 row in set (0.00 sec) mysql主从已经搭建好，接下来就是测试主从复制是否成功;
测试阶段：
在master上操作： MariaDB [(none)]> create database mydb; Query OK, 1 row affected (0.00 sec) MariaDB [(none)]> use mydb; Database changed MariaDB [mydb]> create table tb1 (id int , name varchar(30), age int); Query OK, 0 rows affected (0.02 sec) MariaDB [mydb]> insert into tb1 (id, name, age) values (1,'hx',20),(2,'yl','21'); Query OK, 2 rows affected (0.01 sec) Records: 2 Duplicates: 0 Warnings: 0 MariaDB [mydb]> select * from tb1; +------+------+------+ | id | name | age | +------+------+------+ | 1 | hx | 20 | | 2 | yl | 21 | +------+------+------+ 2 rows in set (0.00 sec)
在slave上测试，查看是否同步过来. MariaDB [(none)]> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | mydb | | mysql | | performance_schema | | test | +--------------------+ 5 rows in set (0.00 sec) MariaDB [(none)]> use mydb; Database changed MariaDB [mydb]> show tables; +----------------+ | Tables_in_mydb | +----------------+ | tb1 | +----------------+ 1 row in set (0.00 sec) MariaDB [mydb]> select * from tb1; +------+------+------+ | id | name | age | +------+------+------+ | 1 | hx | 20 | | 2 | yl | 21 | +------+------+------+ 2 rows in set (0.00 sec) MariaDB [mydb]> show slave status \G *************************** 1. row *************************** Slave_IO_State: Waiting for master to send event Master_Host: 192.168.155.12 Master_User: repluser Master_Port: 3306 Connect_Retry: 60 Master_Log_File: mysql-bin.000004 Read_Master_Log_Pos: 893 Relay_Log_File: relay-log.000002 Relay_Log_Pos: 922 Relay_Master_Log_File: mysql-bin.000004 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: 893 Relay_Log_Space: 1210 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 ##没发现有延迟 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: 1 1 row in set (0.00 sec) slave以及同步了maste的数据库、表、以及数据.
结论： 因为数据量很小，虽然是个异步复制的过程，但是我们可以感觉到复制的速度很快，和同步没有两样。 在我们的生产环境，也是使用mysql主从数据。因为insert,update,delete是操作会比较频繁，会有5-10秒的延迟时间. 主从同步的过程中，也会出现主从数据不一致的问题。这样可能就需要你重新做一遍主从复制了。 有些地方如果理解有错误，可以评论下本文章，一起努力学习及分享。 作者: kattall Q Q : 532461968 感谢: MageEdu
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