MySQL数据库的主从同步和读写分离
1.案例
企业拓扑图
1.在上述拓扑图中，后端MySQL数据库只有一台时，会有以下问题：
单点故障，导致服务不可用
无法处理大量的并发数据请求
数据丢失是大灾难
改造过后企业的拓扑图
2.改造的办法
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增加MySQL数据库的服务器，对数据进行备份，形成主备
确保主备MySQL数据库服务器数据是一样的
主服务器宕机了，备份服务器继续工作，数据有保障
更高级的解决方案的拓扑图
重点：
1.我们需要主从同步账号
2.节点被调度的权限或者账号
3.代理账号
2.主从同步
1.主从同步的类型
1.基于语句的同步（默认）
在主服务器上执行的语句，从服务器执行同样的语句
2.基于行的同步
把改变的内容复制到从服务器
3.混合类型的复制
一旦发现基于语句无法精确复制时，就会采用基于行的复制
2.主从复制的工作过程
3.案例实施
1.配置MySQL master服务器
[root@localhost ~]# hostnamectl set-hostname master
[root@localhost ~]# su
//安装ntp，同步时间
[root@master ~]# yum -y install ntp
//配置ntp的主配置文件
[root@master ~]# vim /etc/ntp.conf
//本地时钟源
server 127.127.195.0
//设置时间层级为8
fudge 127.127.195.0 stratum 8
[root@master ~]# systemctl start ntpd
//关闭防火墙
[root@master ~]# systemctl stop firewalld
[root@master ~]# setenforce 0
//安装MySQL5.7
//安装MySQL的源码编译包
[root@master ~]# yum -y install ncurses ncurses-devel bison cmake gcc gcc-c++
//创建MySQL程序用户
[root@master ~]# useradd -s /sbin/nologin mysql
//将压缩包解压到/opt目录下面
[root@master ~]# tar -zxvf mysql-boost-5.7.20.tar.gz -C /opt
[root@master ~]# cd /opt/mysql-5.7.20/
//cmake 编译安装MySQL5.7
[root@master mysql-5.7.20]# cmake \
-DCMAKE_INSTALL_PREFIX=/usr/local/mysql \
-DMYSQL_UNIX_ADDR=/usr/local/mysql/mysql.sock \
-DSYSCONFDIR=/etc \
-DSYSTEMD_PID_DIR=/usr/local/mysql \
-DDEFAULT_CHARSET=utf8 \
-DDEFAULT_COLLATION=utf8_general_ci \
-DWITH_INNOBASE_STORAGE_ENGINE=1 \
-DWITH_ARCHIVE_STORAGE_ENGINE=1 \
-DWITH_BLACKHOLE_STORAGE_ENGINE=1 \
-DWITH_PERFSCHEMA_STORAGE_ENGINE=1 \
-DMYSQL_DATADIR=/usr/local/mysql/data \
-DWITH_BOOST=boost \
-DWITH_SYSTEMD=1
[root@master mysql-5.7.20]# make
[root@master mysql-5.7.20]# make install
//将/usr/local/mysql目录下面的所有文件的属主和属组都给mysql
[root@master mysql-5.7.20]# chown -R mysql:mysql /usr/local/mysql/
//配置MySQL的my.cnf文件
[root@master mysql-5.7.20]# vi /etc/my.cnf
[client]
port = 3306
default-character-set=utf8
socket = /usr/local/mysql/mysql.sock
[mysql]
port = 3306
default-character-set=utf8
socket = /usr/local/mysql/mysql.sock
[mysqld]
user = mysql
basedir = /usr/local/mysql
datadir = /usr/local/mysql/data
port = 3306
character_set_server=utf8
pid-file = /usr/local/mysql/mysqld.pid
socket = /usr/local/mysql/mysql.sock
server-id = 1
sql_mode=NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES,NO_AUTO_CREATE_USER,NO_AUTO_VALUE_ON_ZERO,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,PIPES_AS_CONCAT,ANSI_QUOTES
//修改my.cnf的属主和属组
[root@master mysql-5.7.20]# chown mysql:mysql /etc/my.cnf
//配置mysql的环境变量
[root@master mysql-5.7.20]# echo 'PATH=/usr/local/mysql/bin:/usr/local/mysql/lib:$PATH' >> /etc/profile
[root@master mysql-5.7.20]# echo 'export PATH' >> /etc/profile
//加载环境变量
[root@master mysql-5.7.20]# source /etc/profile
//初始化mysql数据库
[root@master mysql-5.7.20]# cd /usr/local/mysql/
[root@master mysql]# bin/mysqld \
--initialize-insecure \
--user=mysql \
--basedir=/usr/local/mysql \
--datadir=/usr/local/mysql/data
[root@master mysql]# cp usr/lib/systemd/system/mysqld.service /usr/lib/systemd/system/
[root@master mysql]# systemctl enable mysqld
Created symlink from /etc/systemd/system/multi-user.target.wants/mysqld.service to /usr/lib/systemd/system/mysqld.service.
[root@master mysql]# netstat -ntap | grep 3306
tcp6 0 0 :::3306 :::* LISTEN 22547/mysqld
[root@master mysql]# vim /etc/my.cnf
server-id = 11
log-bin=master-bin
log-slave-updates=true
[root@master mysql]# systemctl restart mysqld
[root@master ~]# mysql -uroot -pabc123
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 3
Server version: 5.7.20-log Source distribution
Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql> grant replication slave on *.* to 'myslave'@'192.168.73.%' identified by '123456';
Query OK, 0 rows affected, 1 warning (0.01 sec)
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)
mysql> show master status;
+-------------------+----------+--------------+------------------+-------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+-------------------+----------+--------------+------------------+-------------------+
| master-bin.000001 | 604 | | | |
+-------------------+----------+--------------+------------------+-------------------+
1 row in set (0.00 sec)
mysql> grant all on *.* to test@'192.168.73.%' identified by '123.com';
Query OK, 0 rows affected, 1 warning (0.00 sec)
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)
2.配置MySQL从服务器slave1
//MySQL5.7的安装参照master的安装
[root@localhost mysql]# hostnamectl set-hostname slave1
[root@localhost mysql]# su
[root@slave1 mysql]# yum -y install ntp ntpdate
[root@slave1 mysql]# systemctl stop firewalld
[root@slave1 mysql]# setenforce 0
[root@slave1 mysql]# /usr/sbin/ntpdate 192.168.73.141
9 Jan 11:16:04 ntpdate[5477]: the NTP socket is in use, exiting
[root@slave1 mysql]# vim /etc/my.cnf
server-id = 22
relay-log=relay-log-bin
relay-log-index=slave-relay-bin.index
[root@slave1 mysql]# systemctl restart mysqld
[root@slave1 mysql]# mysql -u root -pabc123
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 3
Server version: 5.7.20 Source distribution
Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql> change master to master_host='192.168.73.141',master_user='myslave',master_password='123456'',master_log_file='master-bin.000001',master_log_pos=604;
Query OK, 0 rows affected, 2 warnings (0.04 sec)
mysql> start slave;
Query OK, 0 rows affected (0.00 sec)
mysql> grant all on *.* to test@'192.168.73.%' identified by '123.com';
Query OK, 0 rows affected, 1 warning (0.01 sec)
mysql> show slave status\G;
*************************** 1. row ***************************
Slave_IO_State: Connecting to master
Master_Host: 192.168.73.141
Master_User: myslave
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: master-bin.000001
Read_Master_Log_Pos: 604
Relay_Log_File: relay-log-bin.000001
Relay_Log_Pos: 4
Relay_Master_Log_File: master-bin.000001
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: 604
Relay_Log_Space: 154
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: 1130
Last_IO_Error: error connecting to master '[email protected]:3306' - retry-time: 60 retries: 9
Last_SQL_Errno: 0
Last_SQL_Error:
Replicate_Ignore_Server_Ids:
Master_Server_Id: 0
Master_UUID:
Master_Info_File: /usr/local/mysql/data/master.info
SQL_Delay: 0
SQL_Remaining_Delay: NULL
Slave_SQL_Running_State: Slave has read all relay log; waiting for more updates
Master_Retry_Count: 86400
Master_Bind:
Last_IO_Error_Timestamp: 200109 11:29:56
Last_SQL_Error_Timestamp:
Master_SSL_Crl:
Master_SSL_Crlpath:
Retrieved_Gtid_Set:
Executed_Gtid_Set:
Auto_Position: 0
Replicate_Rewrite_DB:
Channel_Name:
Master_TLS_Version:
1 row in set (0.00 sec)
mysql> grant all on *.* to test@'192.168.73.%' identified by '123.com';
Query OK, 0 rows affected, 1 warning (0.00 sec)
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)
3.配置MySQL从服务器slave2
[root@localhost mysql]# hostnamectl set-hostname slave2
[root@localhost mysql]# su
[root@slave2 mysql]# yum -y install ntp ntpdate
[root@slave2 mysql]# systemctl start ntpd
[root@slave2 mysql]# systemctl stop firewalld
[root@slave2 mysql]# setenforce 0
[root@slave2 mysql]# /usr/sbin/ntpdate 192.168.73.141
9 Jan 11:27:05 ntpdate[23734]: the NTP socket is in use, exiting
[root@slave2 mysql]# vim /etc/my.cnf
server-id = 23
relay-log=relay-log-bin
relay-log-index=slave-relay-bin.index
[root@slave2 mysql]# systemctl restart mysqld
[root@slave2 mysql]# mysql -uroot -pabc123
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 3
Server version: 5.7.20 Source distribution
Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql> change master to master_host='192.168.73.141',master_user='myslave',master_password='123456',master_log_file='master-bin.000001',master_log_pos=604;
Query OK, 0 rows affected, 2 warnings (0.12 sec)
mysql> start slave;
Query OK, 0 rows affected (0.01 sec)
mysql> show slave status\G;
*************************** 1. row ***************************
Slave_IO_State: Connecting to master
Master_Host: 192.168.73.141
Master_User: myslave
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: master-bin.000001
Read_Master_Log_Pos: 604
Relay_Log_File: relay-log-bin.000001
Relay_Log_Pos: 4
Relay_Master_Log_File: master-bin.000001
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: 604
Relay_Log_Space: 154
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: 1130
Last_IO_Error: error connecting to master '[email protected]:3306' - retry-time: 60 retries: 1
Last_SQL_Errno: 0
Last_SQL_Error:
Replicate_Ignore_Server_Ids:
Master_Server_Id: 0
Master_UUID:
Master_Info_File: /usr/local/mysql/data/master.info
SQL_Delay: 0
SQL_Remaining_Delay: NULL
Slave_SQL_Running_State: Slave has read all relay log; waiting for more updates
Master_Retry_Count: 86400
Master_Bind:
Last_IO_Error_Timestamp: 200109 11:33:22
Last_SQL_Error_Timestamp:
Master_SSL_Crl:
Master_SSL_Crlpath:
Retrieved_Gtid_Set:
Executed_Gtid_Set:
Auto_Position: 0
Replicate_Rewrite_DB:
Channel_Name:
Master_TLS_Version:
1 row in set (0.00 sec)
mysql> grant all on *.* to test@'192.168.73.%' identified by '123.com';
Query OK, 0 rows affected, 1 warning (0.00 sec)
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)
4.测试主从同步
在master主机上
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
+--------------------+
4 rows in set (0.11 sec)
mysql> create database school;
Query OK, 1 row affected (0.10 sec)
mysql> use school;
Database changed
mysql> create table info (id int,name char(20));
Query OK, 0 rows affected (0.01 sec)
mysql> insert into info (id,name) values(1,'1hao');
Query OK, 1 row affected (0.01 sec)
mysql> insert into info (id,name) values(2,'2hao');
Query OK, 1 row affected (0.01 sec)
mysql> select * from info;
+------+------+
| id | name |
+------+------+
| 1 | 1hao |
| 2 | 2hao |
+------+------+
2 rows in set (0.00 sec)
在slave1主机上
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| school |
| sys |
+--------------------+
5 rows in set (0.00 sec)
mysql> use school;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql> select * from info;
+------+------+
| id | name |
+------+------+
| 1 | 1hao |
| 2 | 2hao |
+------+------+
2 rows in set (0.00 sec)
在slave2主机上
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| school |
| sys |
+--------------------+
5 rows in set (0.00 sec)
mysql> use school;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql> select * from info;
+------+------+
| id | name |
+------+------+
| 1 | 1hao |
| 2 | 2hao |
+------+------+
2 rows in set (0.00 sec)
3.读写分离
1.读写分离的原理
1.读写分离就是只在主服务器上写，只在从服务器上读
2.主数据库处理事务性查询，而从数据库处理select查询
3.数据库复制被用来把事务性查询导致的变更同步到集群中的从数据库
2.案例实施
1.搭建amoeba代理服务器
[root@localhost ~]# hostnamectl set-hostname amoeba
[root@localhost ~]# su
[root@amoeba ~]# ls
amoeba-mysql-binary-2.2.0.tar.gz jdk-6u14-linux-x64.bin 模板 文档 桌面
anaconda-ks.cfg mysql-boost-5.7.20.tar.gz 视频 下载
initial-setup-ks.cfg 公共 图片 音乐
[root@amoeba ~]# systemctl stop firewalld
[root@amoeba ~]# setenforce 0
[root@amoeba ~]# cp jdk-6u14-linux-x64.bin /usr/local
[root@amoeba ~]# cd /usr/local
[root@amoeba local]# ls
bin etc games include jdk-6u14-linux-x64.bin lib lib64 libexec mysql sbin share src
[root@amoeba local]# chmod +x jdk-6u14-linux-x64.bin
[root@amoeba local]# ./jdk-6u14-linux-x64.bin
Please enter "yes" or "no".
Do you agree to the above license terms? [yes or no]
yes
[root@amoeba local]# ls
bin games jdk1.6.0_14 lib libexec sbin src
etc include jdk-6u14-linux-x64.bin lib64 mysql share
[root@amoeba local]# mv jdk1.6.0_14/ jdk1.6
[root@amoeba local]# ls
bin games jdk1.6 lib libexec sbin src
etc include jdk-6u14-linux-x64.bin lib64 mysql share
[root@amoeba local]# echo '
> export JAVA_HOME=/usr/local/jdk1.6
> export CLASSPATH=$CLASSPATH:$JAVA_HOME/lib:$JAVA_HOME/jre/lib
> export PATH=$JAVA_HOME/lib:$JAVA_HOME/jre/bin:$PATH:$HOME/bin
> export AMOEBA_HOME=/usr/local/amoeba
> export PATH=$PATH:$AMOEBA_HOME/bin' >> /etc/profile
[root@amoeba local]# source /etc/profile
[root@amoeba local]# java -version
java version "1.6.0_14"
Java(TM) SE Runtime Environment (build 1.6.0_14-b08)
Java HotSpot(TM) 64-Bit Server VM (build 14.0-b16, mixed mode)
[root@amoeba local]# mkdir /usr/local/amoeba
[root@amoeba local]# cd
[root@amoeba ~]# tar -zxvf amoeba-mysql-binary-2.2.0.tar.gz -C /usr/local/amoeba
[root@amoeba ~]# chmod -R 755 /usr/local/amoeba
[root@amoeba ~]# /usr/local/amoeba/bin/amoeba
amoeba start|stop
[root@amoeba ~]# cd /usr/local/amoeba
[root@amoeba amoeba]# vim conf/amoeba.xml
30 <property name="user">amoeba</property>
31
32 <property name="password">123456</property>
117 <property name="defaultPool">master</property>
118 <property name="writePool">master</property>
119 <property name="readPool">slaves</property>
[root@amoeba amoeba]# vim conf/amoeba.xml
26 <property name="user">test</property>
27
28
29 <property name="password">123.com</property>
45 <dbServer name="user" parent="abstractServer">
46 <factoryConfig>
47 <!-- mysql ip -->
48 <property name="ipAddress">192.168.73.141</property>
49 </factoryConfig>
50 </dbServer>
45 <dbServer name="master" parent="abstractServer">
46 <factoryConfig>
47 <!-- mysql ip -->
48 <property name="ipAddress">192.168.73.141</property>
49 </factoryConfig>
50 </dbServer>
51
52 <dbServer name="slave1" parent="abstractServer">
53 <factoryConfig>
54 <!-- mysql ip -->
55 <property name="ipAddress">192.168.73.138</property>
56 </factoryConfig>
57 </dbServer>
58
59 <dbServer name="slave2" parent="abstractServer">
60 <factoryConfig>
61 <!-- mysql ip -->
62 <property name="ipAddress">192.168.73.142</property>
63 </factoryConfig>
64 </dbServer>
65
66 <dbServer name="slaves" virtual="true">
67 <poolConfig class="com.meidusa.amoeba.server.MultipleServerPool">
68 <!-- Load balancing strategy: 1=ROUNDROBIN , 2=WEIGHTBASED , 3=HA-->
69 <property name="loadbalance">1</property>
70
71 <!-- Separated by commas,such as: server1,server2,server1 -->
72 <property name="poolNames">slave1,slave2</property>
73 </poolConfig>
74 </dbServer>
[root@amoeba ~]# netstat -ntap | grep java
tcp6 0 0 :::8066 :::* LISTEN 6097/java
tcp6 0 0 127.0.0.1:24038 :::* LISTEN 6097/java
tcp6 37 0 192.168.73.140:45008 192.168.73.141:3306 CLOSE_WAIT 5838/java
tcp6 0 0 192.168.73.140:42792 192.168.73.141:3306 ESTABLISHED 5975/java
tcp6 0 0 192.168.73.140:54100 192.168.73.142:3306 ESTABLISHED 6097/java
tcp6 0 0 192.168.73.140:35558 192.168.73.138:3306 ESTABLISHED 5975/java
tcp6 0 0 192.168.73.140:44924 192.168.73.141:3306 ESTABLISHED 6097/java
tcp6 0 0 192.168.73.140:51968 192.168.73.142:3306 ESTABLISHED 5975/java
tcp6 0 0 192.168.73.140:37690 192.168.73.138:3306 ESTABLISHED 6097/java
2.在客户机上面
[root@localhost ~]# hostnamectl set-hostname client
[root@localhost ~]# su
[root@client ~]# yum -y install mysql
[root@client ~]# systemctl stop firewalld
[root@client ~]# setenforce 0
[root@client ~]# mysql -u amoeba -p 123456 -h 192.168.73.140 -P8066
Enter password: \\密码123456
Welcome to the MariaDB monitor. Commands end with ; or \g.
Your MySQL connection id is 1218932998
Server version: 5.1.45-mysql-amoeba-proxy-2.2.0
Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
MySQL [(none)]> show databases;
ERROR 2006 (HY000): MySQL server has gone away
No connection. Trying to reconnect...
Connection id: 1218932998
Current database: *** NONE ***
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| school |
| sys |
+--------------------+
5 rows in set (0.01 sec)
MySQL [(none)]> use school;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
MySQL [school]> select * from info;
+------+------+
| id | name |
+------+------+
| 1 | 1hao |
| 2 | 2hao |
+------+------+
2 rows in set (0.01 sec)
3.关闭slave的slave
//slave2
[root@slave1 ~]# mysql -uroot -pabc123
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 1534
Server version: 5.7.20 Source distribution
Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql> stop slave;
Query OK, 0 rows affected (0.01 sec)
mysql> use school;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql> insert into info (id,name) values(4,'4hao');
Query OK, 1 row affected (0.01 sec)
//slave1
[root@slave1 ~]# mysql -uroot -pabc123
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 1534
Server version: 5.7.20 Source distribution
Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql> stop slave;
Query OK, 0 rows affected (0.01 sec)
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| school |
| sys |
+--------------------+
5 rows in set (0.00 sec)
mysql> use school;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql> insert into info (id,name) values (3,'3hao');
Query OK, 1 row affected (0.00 sec)
4.在client里面测试
MySQL [school]> select * from info;
+------+------+
| id | name |
+------+------+
| 1 | 1hao |
| 2 | 2hao |
| 4 | 4hao |
+------+------+
3 rows in set (0.02 sec)
MySQL [school]> select * from info;
+------+------+
| id | name |
+------+------+
| 1 | 1hao |
| 2 | 2hao |
| 3 | 3hao |
+------+------+
3 rows in set (0.01 sec)
MySQL [school]> select * from info;
+------+------+
| id | name |
+------+------+
| 1 | 1hao |
| 2 | 2hao |
| 4 | 4hao |
+------+------+
3 rows in set (0.00 sec)
MySQL [school]> select * from info;
+------+------+
| id | name |
+------+------+
| 1 | 1hao |
| 2 | 2hao |
| 3 | 3hao |
+------+------+
3 rows in set (0.00 sec)
从这个测试中，我们可以看出： MySQL对读请求做了负载均衡，对多次请求采用了轮询算法，所有的用于处理读请求的MySQL会轮流(或者按权重)来响应 。
