mycat结合MySQL双主实现读写分离

Posted 2021-05-02 DevOps视角

作者介绍

牛恒博，一线运维人，擅长为中小企业快速实现运维从无到有，再到自动化。现就职于某医疗大数据公司。

服务器拓扑

服务器架构

主机名	IP	功能	备注
linux-node1	192.168.56.11	mycat	要安装mysql不需启动
linux-node2	192.168.56.12	mysql-master1,mysql-slave1	slave1端口：3307
linux-node2	192.168.56.13	mysql-master2,mysql-slave2	slave2端口：3307

安装MySQL

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

修改my.cnf

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

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

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

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

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

启动服务

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

ss -lntup |egrep '3306|3307'
tcp    LISTEN     0      80                     *:3306                  *:*      users:(("mysqld",19973,22))
tcp    LISTEN     0      80                     *:3307                  *:*      users:(("mysqld",20537,22))

配置双主

配置主从

linux-node2

master

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

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

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

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

配置双主

master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)

linux-node2 master配置跟linux-node3 master同步

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;
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                

linux-node3 master配置跟linux-node2 master同步

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;
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

验证

从linux-node2上验证

在linux-node2 master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)

在linux-node2 slave上查看数据

mysql> select * from test.temp;
+------+------+
| id   | name |
+------+------+
|    1 | aaa  |
+------+------+
1 row in set (0.00 sec)

在linux-node3 master上查看数据

mysql> select * from test.temp;
+------+------+
| id   | name |
+------+------+
|    1 | aaa  |
+------+------+
1 row in set (0.00 sec)

在linux-node3 slave上查看数据

mysql> select * from test.temp;
+------+------+
| id   | name |
+------+------+
|    1 | aaa  |
+------+------+
1 row in set (0.00 sec)

从linux-node3上验证

在linux-node3 master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linux-node3 slave上查看数据

mysql> select * from test.temp2;
+----+-------+
| id | nname |
+----+-------+
|  1 | bbb   |
|  2 | ddd   |
|  4 | fff   |
+----+-------+
3 rows in set (0.00 sec)

在linux-node2 master上查看数据

mysql> select * from test.temp2;
+----+-------+
| id | nname |
+----+-------+
|  1 | bbb   |
|  2 | ddd   |
|  4 | fff   |
+----+-------+
3 rows in set (0.00 sec)

在linux-node2 slave上查看数据

mysql> select * from test.temp2;
+----+-------+
| id | nname |
+----+-------+
|  1 | bbb   |
|  2 | ddd   |
|  4 | fff   |
+----+-------+
3 rows in set (0.00 sec)

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

linux-node1上安装mycat

安装mycat

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

• 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"
  默认值为1，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

./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

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)

在mycat服务器上安装mysql服务，但是不启动

步骤省略，详细内容可以参考上面的MySQL安装

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)

结果发现数据写入到了linux-node2 slave端

测试

服务自动迁移

关闭linux-node2 master的MySQL服务

mysql> shutdown;
Query OK, 0 rows affected (0.01 sec)

shell > ss -lntup |grep 3306

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)

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)

      发现因为linux-node2的master端已经挂了，数据不能同步了

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)

      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

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