mycat结合双主复制实现读写分离模式
简介：应用程序仅需要连接mycat，后端服务器的读写分离由mycat进行控制，后端服务器数据的同步由MySQL主从同步进行控制。
本次实验环境架构图
服务器主机规划
| 主机名 | IP | 功能 | 备注 |
|---|---|---|---|
| linux-node1 | 192.168.56.11 | mycat | 需要安装MySQL不用启动 |
| linux-node2 | 192.168.56.12 | mysql-master1,mysql-slave1 | slave1端口：3307 |
| linux-node3 | 192.168.56.13 | mysql-master2,mysql-slave2 | slave2端口：3307 |
实战演示
安装MySQL数据库
创建mysql用户
groupadd mysql
useradd -r -g mysql -s /bin/false mysql
安装MySQL
yum install -y libaio
cd /usr/local/src/
wget http://mirrors.sohu.com/mysql/MySQL-5.7/mysql-5.7.17-linux-glibc2.5-x86_64.tar.gz
tar -zxf mysql-5.7.17-linux-glibc2.5-x86_64.tar.gz
cp -rf mysql-5.7.17-linux-glibc2.5-x86_64 /data/app/mysql-3306
cp -rf mysql-5.7.17-linux-glibc2.5-x86_64 /data/app/mysql-3307
chown -R mysql:mysql /data/app/mysql-3306
chown -R mysql:mysql /data/app/mysql-3307
/data/app/mysql-3306/bin/mysqld --initialize-insecure --user=mysql --basedir=/data/app/mysql-3306 --datadir=/data/app/mysql-3306/data
/data/app/mysql-3307/bin/mysqld --initialize-insecure --user=mysql --basedir=/data/app/mysql-3307 --datadir=/data/app/mysql-3307/data
生成my.cnf 配置文件
需要修改的参数：
- server-id：保证每个配置文件唯一。
- 两台master的自增长ID必须不同。
linux-node2
master端
cat > /data/app/mysql-3306/my.cnf<<EOF
[client]
port = 3306
socket = /data/app/mysql-3306/mysql.sock
[mysqld]
port = 3306
user = mysql
server-id = 1
bind-address = 0.0.0.0
basedir = /data/app/mysql-3306
datadir = /data/app/mysql-3306/data
socket = /data/app/mysql-3306/mysql.sock
pid-file = /data/app/mysql-3306/mysql.pid
log-error = /data/app/mysql-3306/mysqld.log
skip-name-resolve
log_bin = mysql-bin
log-slave-updates
auto-increment-increment = 2
auto-increment-offset = 1
sql_mode=NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES
EOF
chown mysql.mysql /data/app/mysql-3306/my.cnf
slave端
cat > /data/app/mysql-3307/my.cnf<<EOF
[client]
port = 3307
socket = /data/app/mysql-3307/mysql.sock
[mysqld]
port = 3307
user = mysql
server-id = 11
bind-address = 0.0.0.0
basedir = /data/app/mysql-3307
datadir = /data/app/mysql-3307/data
socket = /data/app/mysql-3307/mysql.sock
pid-file = /data/app/mysql-3307/mysql.pid
log-error = /data/app/mysql-3307/mysqld.log
skip-name-resolve
log_bin = mysql-bin
sql_mode=NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES
EOF
chown mysql.mysql /data/app/mysql-3307/my.cnf
linux-node3
master端
cat > /data/app/mysql-3306/my.cnf<<EOF
[client]
port = 3306
socket = /data/app/mysql-3306/mysql.sock
[mysqld]
port = 3306
user = mysql
server-id = 2
bind-address = 0.0.0.0
basedir = /data/app/mysql-3306
datadir = /data/app/mysql-3306/data
socket = /data/app/mysql-3306/mysql.sock
pid-file = /data/app/mysql-3306/mysql.pid
log-error = /data/app/mysql-3306/mysqld.log
skip-name-resolve
log_bin = mysql-bin
log-slave-updates
auto-increment-increment = 2
auto-increment-offset = 2
sql_mode=NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES
EOF
chown mysql.mysql /data/app/mysql-3306/my.cnf
slave 端
cat > /data/app/mysql-3307/my.cnf<<EOF
[client]
port = 3307
socket = /data/app/mysql-3307/mysql.sock
[mysqld]
port = 3307
user = mysql
server-id = 22
bind-address = 0.0.0.0
basedir = /data/app/mysql-3307
datadir = /data/app/mysql-3307/data
socket = /data/app/mysql-3307/mysql.sock
pid-file = /data/app/mysql-3307/mysql.pid
log-error = /data/app/mysql-3307/mysqld.log
skip-name-resolve
log_bin = mysql-bin
sql_mode=NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES
EOF
chown mysql.mysql /data/app/mysql-3307/my.cnf
启动MySQL进程
linux-node2和linux-node3都执行如下命令
touch /data/app/mysql-3306/mysqld.log && chown mysql.mysql /data/app/mysql-3306/mysqld.log
sed -i 's#/usr/local/mysql#/data/app/mysql-3306#g' /data/app/mysql-3306/bin/mysqld_safe
/data/app/mysql-3306/bin/mysqld_safe --defaults-file=/data/app/mysql-3306/my.cnf --basedir=/data/app/mysql-3306 --datadir=/data/app/mysql-3306/data --user=mysql &
touch /data/app/mysql-3307/mysqld.log && chown mysql.mysql /data/app/mysql-3307/mysqld.log
sed -i 's#/usr/local/mysql#/data/app/mysql-3307#g' /data/app/mysql-3307/bin/mysqld_safe
/data/app/mysql-3307/bin/mysqld_safe --defaults-file=/data/app/mysql-3307/my.cnf --basedir=/data/app/mysql-3307 --datadir=/data/app/mysql-3307/data --user=mysql &
检查端口是否正常
ss -lntup |egrep '3306|3307'
tcp LISTEN 0 80 *:3306 *:* users:(("mysqld",19973,22))
tcp LISTEN 0 80 *:3307 *:* users:(("mysqld",20537,22))
MySQL双主配置
第一步先配置主从模式
linux-node2
master端
cd /data/app/mysql-3306/
./bin/mysql -uroot -p -S mysql.sock -P 3306
mysql> CREATE USER 'repl'@'192.%' IDENTIFIED BY 'mysql';
Query OK, 0 rows affected (0.05 sec)
mysql> GRANT REPLICATION SLAVE ON *.* TO 'repl'@'192.%';
Query OK, 0 rows affected (0.00 sec)
mysql> show master status;
+------------------+----------+--------------+------------------+-------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+------------------+----------+--------------+------------------+-------------------+
| mysql-bin.000001 | 613 | | | |
+------------------+----------+--------------+------------------+-------------------+
1 row in set (0.00 sec)
slave端
cd /data/app/mysql-3307/
./bin/mysql -uroot -p -S mysql.sock -P 3307
mysql> CHANGE MASTER TO MASTER_HOST='192.168.56.12',
-> MASTER_PORT=3306,
-> MASTER_USER='repl',
-> MASTER_PASSWORD='mysql',
-> MASTER_LOG_FILE='mysql-bin.000001',
-> MASTER_LOG_POS=613;
Query OK, 0 rows affected, 2 warnings (0.04 sec)
mysql> start slave;
Query OK, 0 rows affected (0.02 sec)
mysql> show slave status\G
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 192.168.56.12
Master_User: repl
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000001
Read_Master_Log_Pos: 613
Relay_Log_File: linux-node2-relay-bin.000002
Relay_Log_Pos: 320
Relay_Master_Log_File: mysql-bin.000001
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
linux-node3
master端
cd /data/app/mysql-3306/
./bin/mysql -uroot -p -S mysql.sock -P 3306
mysql> CREATE USER 'repl'@'192.%' IDENTIFIED BY 'mysql';
Query OK, 0 rows affected (0.05 sec)
mysql> GRANT REPLICATION SLAVE ON *.* TO 'repl'@'192.%';
Query OK, 0 rows affected (0.00 sec)
mysql> show master status;
+------------------+----------+--------------+------------------+-------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+------------------+----------+--------------+------------------+-------------------+
| mysql-bin.000001 | 613 | | | |
+------------------+----------+--------------+------------------+-------------------+
1 row in set (0.00 sec)
slave端
cd /data/app/mysql-3307/
./bin/mysql -uroot -p -S mysql.sock -P 3307
mysql>
CHANGE MASTER TO MASTER_HOST='192.168.56.13',
MASTER_PORT=3306,
MASTER_USER='repl',
MASTER_PASSWORD='mysql',
MASTER_LOG_FILE='mysql-bin.000001',
MASTER_LOG_POS=613;
Query OK, 0 rows affected, 2 warnings (0.04 sec)
mysql> start slave;
Query OK, 0 rows affected (0.02 sec)
mysql> show slave status\G
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 192.168.56.13
Master_User: repl
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000001
Read_Master_Log_Pos: 613
Relay_Log_File: linux-node2-relay-bin.000002
Relay_Log_Pos: 320
Relay_Master_Log_File: mysql-bin.000001
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
第二步配置双主模式
检查两个master端的binlog位置
linux-node2 master端
cd /data/app/mysql-3306/
./bin/mysql -uroot -p -S mysql.sock -P 3306
mysql> show master status;
+------------------+----------+--------------+------------------+-------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+------------------+----------+--------------+------------------+-------------------+
| mysql-bin.000001 | 613 | | | |
+------------------+----------+--------------+------------------+-------------------+
1 row in set (0.00 sec)
linux-node3 master端
cd /data/app/mysql-3306/
./bin/mysql -uroot -p -S mysql.sock -P 3306
mysql> show master status;
+------------------+----------+--------------+------------------+-------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+------------------+----------+--------------+------------------+-------------------+
| mysql-bin.000001 | 613 | | | |
+------------------+----------+--------------+------------------+-------------------+
1 row in set (0.00 sec)
node2-master 上配置跟node3同步
CHANGE MASTER TO MASTER_HOST='192.168.56.13',
MASTER_PORT=3306,
MASTER_USER='repl',
MASTER_PASSWORD='mysql',
MASTER_LOG_FILE='mysql-bin.000001',
MASTER_LOG_POS=613;
mysql> start slave;
Query OK, 0 rows affected (0.03 sec)
mysql> show slave status\G
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 192.168.56.13
Master_User: repl
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000001
Read_Master_Log_Pos: 613
Relay_Log_File: linux-node2-relay-bin.000002
Relay_Log_Pos: 320
Relay_Master_Log_File: mysql-bin.000001
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
node3-master 上配置跟node2同步
CHANGE MASTER TO MASTER_HOST='192.168.56.12',
MASTER_PORT=3306,
MASTER_USER='repl',
MASTER_PASSWORD='mysql',
MASTER_LOG_FILE='mysql-bin.000001',
MASTER_LOG_POS=613;
mysql> start slave;
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql> show slave status\G
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 192.168.56.12
Master_User: repl
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000001
Read_Master_Log_Pos: 613
Relay_Log_File: linux-node3-relay-bin.000002
Relay_Log_Pos: 320
Relay_Master_Log_File: mysql-bin.000001
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
开始验证结果
在node2-master主机上创建数据
mysql> create database test;
Query OK, 1 row affected (0.01 sec)
mysql> use test;
Database changed
mysql> create table temp(id int,name varchar(64));
Query OK, 0 rows affected (0.11 sec)
mysql> insert into temp values(1,'aaa');
Query OK, 1 row affected (0.28 sec)
mysql> CREATE TABLE temp2(id INT PRIMARY KEY NOT NULL AUTO_INCREMENT ,nname VARCHAR(64));
Query OK, 0 rows affected (0.01 sec)
mysql> insert into temp2(nname) values('bbb');
Query OK, 1 row affected (0.01 sec)
mysql> select * from test.temp;
+------+------+
| id | name |
+------+------+
| 1 | aaa |
+------+------+
1 row in set (0.01 sec)
mysql>
在node2-slave端查看数据是否存在
mysql> select * from test.temp;
+------+------+
| id | name |
+------+------+
| 1 | aaa |
+------+------+
1 row in set (0.00 sec)
mysql>
在node3-master端查看数据是否存在
mysql> select * from test.temp;
+------+------+
| id | name |
+------+------+
| 1 | aaa |
+------+------+
1 row in set (0.00 sec)
mysql>
在node3-slave端查看数据是否存在
mysql> select * from test.temp;
+------+------+
| id | name |
+------+------+
| 1 | aaa |
+------+------+
1 row in set (0.00 sec)
mysql>
在node3-master主机上创建数据
mysql> use test;
mysql> insert into temp2(nname) values('ddd');
Query OK, 1 row affected (0.02 sec)
mysql> insert into temp2(nname) values('fff');
Query OK, 1 row affected (0.00 sec)
mysql> select * from test.temp2;
+----+-------+
| id | nname |
+----+-------+
| 1 | bbb |
| 2 | ddd |
| 4 | fff |
+----+-------+
3 rows in set (0.00 sec)
在node3-slave端查看数据是否存在
mysql> select * from test.temp2;
+----+-------+
| id | nname |
+----+-------+
| 1 | bbb |
| 2 | ddd |
| 4 | fff |
+----+-------+
3 rows in set (0.00 sec)
mysql>
在node2-master端查看数据是否存在
mysql> select * from test.temp2;
+----+-------+
| id | nname |
+----+-------+
| 1 | bbb |
| 2 | ddd |
| 4 | fff |
+----+-------+
3 rows in set (0.00 sec)
mysql>
在node2-slave端查看数据是否存在
mysql> select * from test.temp2;
+----+-------+
| id | nname |
+----+-------+
| 1 | bbb |
| 2 | ddd |
| 4 | fff |
+----+-------+
3 rows in set (0.00 sec)
mysql>
结论
- 在任意一个master端更新数据，其他任意端都可以更新数据。
- 两台服务器配置了间隔自增长，数据不同冲突。
mycat安装
cd /usr/local/src
wget http://dl.mycat.io/1.6-RELEASE/Mycat-server-1.6-RELEASE-20161028204710-linux.tar.gz
tar -zxf Mycat-server-1.6-RELEASE-20161028204710-linux.tar.gz
mv mycat /data/app/mycat-1.6
ln -s /data/app/mycat-1.6 /data/app/mycat
修改schema.xml 的配置文件
balance="1": 全部的readHost与stand by writeHost参与select语句的负载均衡。writeType="0": 所有写操作发送到配置的第一个writeHost，第一个挂了切到还生存的第二个 writeHost，重新启动后以切换后的为准，切换记录在配置文件中:dnindex.properties 。switchType="1": 1 默认值，自动切换。
cd /data/app/mycat
cp conf/schema.xml conf/schema.xml.bak
cat > conf/schema.xml <<EOF
<?xml version="1.0"?>
<!DOCTYPE mycat:schema SYSTEM "schema.dtd">
<mycat:schema xmlns:mycat="http://io.mycat/">
<schema name="TESTDB" checkSQLschema="true" sqlMaxLimit="100" dataNode="dn1"></schema>
<dataNode name="dn1" dataHost="node1" database="test" />
<dataHost name="node1" maxCon="10" minCon="5" balance="1" writeType="0" dbType="mysql" dbDriver="native" switchType="1">
<heartbeat>select user()</heartbeat>
<writeHost host="master1" url="192.168.56.12:3306" user="root" password="mysql">
<readHost host="slave2" url="192.168.56.13:3307" user="root" password="mysql" />
</writeHost>
<writeHost host="master2" url="192.168.56.13:3306" user="root" password="mysql">
<readHost host="slave2" url="192.168.56.13:3307" user="root" password="mysql" />
</writeHost>
</dataHost>
</mycat:schema>
EOF
启动mycat服务
./bin/mycat start
ss -lntup |egrep '(8066|9066)'
tcp LISTEN 0 100 :::8066 :::* users:(("java",16546,79))
tcp LISTEN 0 100 :::9066 :::* users:(("java",16546,75))
验证mycat服务是否正常
第一步：在linux-node2-master端配置mycat连接账号
mysql> GRANT ALL PRIVILEGES ON *.* TO root@'192.%' IDENTIFIED BY 'mysql';
Query OK, 0 rows affected, 1 warning (0.07 sec)
第二步：在mycat服务器上安装mysql服务，但是不启动。
具体步骤省略，详细内容可以参考上面的MySQL安装。
第三步：使用mysql的客户端连接mycat
cd /data/app/mysql/
./bin/mysql -uroot -p -P 8066 -h 192.168.56.11 ##连接mycat，初始密码123456
mysql> show databases;
+----------+
| DATABASE |
+----------+
| TESTDB |
+----------+
1 row in set (0.00 sec)
mysql> use TESTDB;
mysql> insert into temp2(nname) values('eee');
Query OK, 1 row affected (0.09 sec)
mysql> insert into temp2(nname) values('ggg');
Query OK, 1 row affected (0.01 sec)
linux-node3-slave 端查看数据是否同步
mysql> select * from test.temp2;
+----+-------+
| id | nname |
+----+-------+
| 1 | bbb |
| 2 | ddd |
| 4 | fff |
| 5 | eee |
| 7 | ggg |
+----+-------+
5 rows in set (0.00 sec)
根据查询结果发现数据写入到了linux-node3-slave端。
测试一台master端挂了服务自动迁移
关闭linux-node2-master的服务
mysql> shutdown;
Query OK, 0 rows affected (0.01 sec)
shell > ss -lntup |grep 3306 ## 确认端口已经关闭。
mycat端插入新的数据查看数据是否同步
mysql> insert into temp2(nname) values('mmmm');
Query OK, 1 row affected (0.07 sec)
mysql> insert into temp2(nname) values('nnnn');
Query OK, 1 row affected (0.01 sec)
linux-node3-slave端查看数据是否同步
mysql> select * from test.temp2;
+----+-------+
| id | nname |
+----+-------+
| 1 | bbb |
| 2 | ddd |
| 4 | fff |
| 5 | eee |
| 7 | ggg |
| 8 | mmmm |
| 10 | nnnn |
+----+-------+
7 rows in set (0.00 sec)
mysql>
linux-node2-slave端查看数据是否同步
mysql> select * from test.temp2;
+----+-------+
| id | nname |
+----+-------+
| 1 | bbb |
| 2 | ddd |
| 4 | fff |
| 5 | eee |
| 7 | ggg |
+----+-------+
5 rows in set (0.00 sec)
mysql>
因为linux-node2的master端已经挂了，故数据不能同步。
测试一台master端挂掉，数据访问是否正常
登录到mycat服务器上执行如下命令：
mysql> select * from temp2;
+----+-------+
| id | nname |
+----+-------+
| 1 | bbb |
| 2 | ddd |
| 4 | fff |
| 5 | eee |
| 7 | ggg |
| 8 | mmmm |
| 10 | nnnn |
+----+-------+
7 rows in set (0.00 sec)
mysql> select * from temp2;
+----+-------+
| id | nname |
+----+-------+
| 1 | bbb |
| 2 | ddd |
| 4 | fff |
| 5 | eee |
| 7 | ggg |
| 8 | mmmm |
| 10 | nnnn |
+----+-------+
7 rows in set (0.00 sec)
执行多次发现结果一样，说明在一台master端挂掉的情况下，其连接的slave端也被剔除，因此数据完整性可以保证。
参考
故障汇总
第一次配置的时候maser端没有配置log-slave-updates导致，node3-slave上没有node2-master端的数据。
解释：
从库开启log-bin参数，如果直接往从库写数据，是可以记录log-bin日志的，但是从库通过I0线程读取主库二进制日志文件，然后通过SQL线程写入的数据，是不会记录binlog日志的。也就是说从库从主库上复制的数据，是不写入从库的binlog日志的。所以从库做为其他从库的主库时需要在配置文件中添加log-slave-updates参数。
解决办法：
[mysqld]
log-slave-updates
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