初识MariaDB之6——半同步复制
Posted
tags:
篇首语:本文由小常识网(cha138.com)小编为大家整理,主要介绍了初识MariaDB之6——半同步复制相关的知识,希望对你有一定的参考价值。
一、背景介绍
mysql主从复制能解决一定的单点故障问题,但其异步的工作特性存在一定的隐患,比如主节点事务提交后还未写入binlog,此时主节点故障后,但主节点认为事务已提交,从节点无法从主节点获取到该事务的信息,提升为主节点后就会造成数据丢失,为了解决这一问题,谷歌为mysql在5.5之后的版本引进了半同步复制
二、原理介绍
所谓半同步复制就是一主多从,或一主一从的时候,主节点事务提交后至少等待一个从节点写入中继日志,这样就保证了当主节点故障后,所有的操作都在中继日志中有保存,当等待从节点的时间超出设置范围,会回复异步的方式
三、环境介绍
本次实验使用CentOS7.4系统,5.5.56-MariaDB,实验拓扑如下图所示:
使用一个日志服务器(也可以是从服务器)作为与主节点半同步的服务器,其他从服务器通过日志服务器同步binlog,由于日志服务器自身只需要记录binlog,所以不需要数据在其上执行一遍,存储引擎可以使用blackhole
四、操作步骤
1.主节点服务器操作
(1)启动主节点服务,配置文件如下
[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
skip_name_resolve=ON
log_bin=mysql-binlog
slow_query_log=ON
server-id=10
innodb_file_per_table=ON
binlog_format=ROW
(2)创建一个主从复制的账号
MariaDB [mysql]> grant replication slave on *.* to 'bak'@'172.16.10.%' identified by 'bakpass';
MariaDB [mysql]> flush privileges;
(3)安装并启动半同步插件(可写入配置文件永久生效)
MariaDB [(none)]> install plugin rpl_semi_sync_master soname 'semisync_master.so';
MariaDB [(none)]> set global rpl_semi_sync_master_enabled=ON;
(4)确认插件和功能以正常启动
MariaDB [(none)]> show global variables like '%semi%';
+------------------------------------+-------+
| Variable_name | Value |
+------------------------------------+-------+
| rpl_semi_sync_master_enabled | ON |
| rpl_semi_sync_master_timeout | 10000 |
| rpl_semi_sync_master_trace_level | 32 |
| rpl_semi_sync_master_wait_no_slave | ON |
+------------------------------------+-------+
MariaDB [(none)]> show plugins;
2.日志服务器操作
(1)启动日志服务器,配置文件如下
[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
skip_name_resolve=ON
relay_log=mysql-relaylog
relay_log_index=mysql-relaylog
read_only=ON
relay_log_purge=ON
slow_query_log=ON
server-id=20
innodb_file_per_table=ON
default_storage_engine=blackhole
binlog_format=ROW
log_bin=mysql-binlog
log_slave_updates=ON
(2)关闭read_only,创建一个主从复制的账号后再开启
MariaDB [(none)]> set global read_only=0;
MariaDB [(none)]> grant replication slave on *.* to 'bak'@'172.16.10.%' identified by 'bakpass';
MariaDB [(none)]> flush privileges;
MariaDB [(none)]> set global read_only=1;
(3)安装并启动半同步插件
MariaDB [(none)]> install plugin rpl_semi_sync_slave soname 'semisync_slave.so';
MariaDB [(none)]> set global rpl_semi_sync_slave_enabled=ON;
(4)确认插件和功能以正常启动
MariaDB [(none)]> show global variables like '%semi%';
+---------------------------------+-------+
| Variable_name | Value |
+---------------------------------+-------+
| rpl_semi_sync_slave_enabled | ON |
| rpl_semi_sync_slave_trace_level | 32 |
+---------------------------------+-------+
MariaDB [(none)]> show plugins;
(5)指定主服务器及主服务器当前的binlog日志和position
MariaDB [hellodb]> change master to
-> master_host='172.16.10.30',
-> master_user='bak',
-> master_password='bakpass',
-> master_port=3306,
-> master_log_file='mysql-binlog.000003',
-> master_log_pos=7805,
-> master_connect_retry=10;
(6)启动从节点(可以指启动指定线程类型,不指定为都启动)
MariaDB [hellodb]> start slave [IO_THREAD | SQL_THREAD];
(7)查看从节点状态(Slave_IO_Running和Slave_SQL_Running显示Yes成功)
MariaDB [(none)]> show slave status \G
3.验证日志服务器blackhole存储引擎是否生效
(1)主节点创建一个数据库及表
MariaDB [(none)]> create database ark;
MariaDB [(none)]> use ark;
MariaDB [ark]> CREATE TABLE `students` ( `StuID` int(10) primary key, `Name` varchar(50) );
(2)确认当前主节点的binlog日志及position
MariaDB [ark]> show master status;
+---------------------+----------+--------------+------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+---------------------+----------+--------------+------------------+
| mysql-binlog.000003 | 8638 | | |
+---------------------+----------+--------------+------------------+
(3)确认日志服务器当前的binlog日志及position
MariaDB [ark]> show master status;
+---------------------+----------+--------------+------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+---------------------+----------+--------------+------------------+
| mysql-binlog.000003 | 1104 | | |
+---------------------+----------+--------------+------------------+
(4)主服务器上任意插入条数据,再次观察主节点的binlog日志及position
MariaDB [ark]> insert into students (stuid,name) values (3,'fu');
MariaDB [ark]> show master status;
+---------------------+----------+--------------+------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+---------------------+----------+--------------+------------------+
| mysql-binlog.000003 | 8818 | | |
+---------------------+----------+--------------+------------------+
(5)在日志服务器上查看中继日志以更新
MariaDB [ark]> show slave status \G
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 172.16.10.30
Master_User: bak
Master_Port: 3306
Connect_Retry: 10
Master_Log_File: mysql-binlog.000003
Read_Master_Log_Pos: 8818
Relay_Log_File: mysql-relaylog.000002
Relay_Log_Pos: 1545
Relay_Master_Log_File: mysql-binlog.000003
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
Exec_Master_Log_Pos: 8818
(6)并且日志服务器上的binlog日志也完成了更新
MariaDB [ark]> show master status;
+---------------------+----------+--------------+------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+---------------------+----------+--------------+------------------+
| mysql-binlog.000003 | 1309 | | |
+---------------------+----------+--------------+------------------+
(7)但此时表中却无任何数据,说明blackhole引擎工作正常
4.从节点服务器操作
从节点就是将日志服务器当成主节点,所有的同步是指向日志服务器
(1)启动从节点的mysql服务,启动relaylog日志,更改serverid
[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
skip_name_resolve=ON
relay_log=mysql-relaylog
relay_log_index=mysql-relaylog
read_only=ON
relay_log_purge=ON
slow_query_log=ON
server-id=30
innodb_file_per_table=ON
(2)指定主服务器及主服务器当前的binlog日志和position
MariaDB [(none)]> change master to
-> master_host='172.16.10.40',
-> master_user='bak',
-> master_password='bakpass',
-> master_port=3306,
-> master_log_file='mysql-binlog.000003',
-> master_log_pos=1309,
-> master_connect_retry=10;
(3)启动从节点(可以指启动指定线程类型,不指定为都启动)
MariaDB [(none)]> start slave [IO_THREAD | SQL_THREAD];
(5)查看从节点状态(Slave_IO_Running和Slave_SQL_Running显示Yes成功)
MariaDB [(none)]> show slave status \G
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 172.16.10.40
Master_User: bak
Master_Port: 3306
Connect_Retry: 10
Master_Log_File: mysql-binlog.000003
Read_Master_Log_Pos: 1309
Relay_Log_File: mysql-relaylog.000002
Relay_Log_Pos: 532
Relay_Master_Log_File: mysql-binlog.000003
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
五、结果验证
(1)在日志服务器查看上游节点
MariaDB [(none)]> show slave hosts;
+-----------+------+------+-----------+
| Server_id | Host | Port | Master_id |
+-----------+------+------+-----------+
| 20 | | 3306 | 10 |
+-----------+------+------+-----------+
(2)在从节点查看上游节点
MariaDB [(none)]> show slave hosts;
+-----------+------+------+-----------+
| Server_id | Host | Port | Master_id |
+-----------+------+------+-----------+
| 30 | | 3306 | 20 |
+-----------+------+------+-----------+
(3)主库上创建个数据库,进行验证,至此操作完成
MariaDB [(none)]> create database wahaha;
MariaDB [(none)]> show status like '%semi%';
Rpl_semi_sync_master_no_tx 没有成功接收slave提交的次数
补充说明:
1.blackhole存储引擎会将所有关于数据的操作丢弃,但是关于数据库结构的操作会执行(如创建数据库,表)
2.Mariadb5.5或者MySQL5.7以后的版本支持多主一从,从服务器可以成为多台MySQL服务器的统一日志服务器,但要求是多台MySQL服务器上数据库名称必须不相同,同时所有从服务器使用不同的复制账号,因为主服务器上每个I/O dump thread都需要用不同的账号发起
MariaDB [(none)]> show processlist \G
*************************** 3. row ***************************
Id: 7
User: bak
Host: 172.16.10.40:47972
db: NULL
Command: Binlog Dump
Time: 15921
State: Master has sent all binlog to slave; waiting for binlog to be updated
Info: NULL
Progress: 0.000
*************************** 5. row ***************************
Id: 17
User: qwe
Host: 172.16.10.50:58968
db: NULL
Command: Binlog Dump
Time: 1866
State: Master has sent all binlog to slave; waiting for binlog to be updated
Info: NULL
Progress: 0.000
3.如果是先开启了主从复制,再切换到半同步,只需要执行
MariaDB [(none)]> stop slave io_thread;
MariaDB [(none)]> start slave io_thread;
4.如果服务器重启,启动MySQL服务器后,plugin插件和主从复制功能会自动启动,但是半同步功能未启动,此时是默认的异步同步(或者配置完成半同步后将该选项写入配置文件),需要手动启动半同步功能和io_thread,执行命令为:
主节点:
MariaDB [(none)]> set global rpl_semi_sync_master_enabled=ON;
从节点:
MariaDB [(none)]> set global rpl_semi_sync_slave_enabled=ON;
MariaDB [(none)]> stop slave io_thread;
MariaDB [(none)]> start slave io_thread;
以上是关于初识MariaDB之6——半同步复制的主要内容,如果未能解决你的问题,请参考以下文章