mycat读写分离与主从切换

1， 分库分表的优缺点、以及为什么分表方式无法成为主流？

分表：在台服务器上，优点是易维护，类似表分区，缺点是在一台db服务器上，无法分担IO、负载集中。
分库：在多台服务器上，优点是分担IO、负载均衡，缺点是较不易维护、数据统计以及jion操作有些难度。

数据库切分的目的是为了分担IO、负载均衡，分表无法达到最佳的要求，所以无法成为主流。

2， 准备主库

tar -xvf mysql-5.6.12.tar.gz
cd mysql-5.6.12

time cmake . -DCMAKE_INSTALL_PREFIX=/usr/local/mysql56m1 -DMYSQL_DATADIR=/home/data/mysql56m1/data -DWITH_INNOBASE_STORAGE_ENGINE=1 -DMYSQL_UNIX_ADDR==/usr/local/mysql56m1/mysql.sock -DMYSQL_USER=mysql -DDEFAULT_CHARSET=utf8 -DDEFAULT_COLLATION=utf8_general_ci

time make
time make install 

 chown -R mysql /home/data/
 chgrp -R mysql /home/data/
 chown -R mysql /usr/local/mysql

 chown -R mysql /usr/local/mysql56m1
 chgrp -R mysql /usr/local/mysql

 chgrp -R mysql /usr/local/mysql56m1/
 mkdir -p /home/data/mysql56m1/binlog/
 chown -R mysql.mysql /home/data/mysql56m1/binlog/
 mkdir -p /home/data/mysql5610/binlog/
 chown -R mysql.mysql /home/data/

cd /usr/local/mysql56m1
time scripts/mysql_install_db  --user=mysql --basedir=/usr/local/mysql56m1 --datadir=/home/data/mysql56m1/data --defaults-file=/usr/local/mysql56m1/my.cnf

cp support-files/mysql.server /etc/init.d/mysql56m1
chmod 700 /etc/init.d/mysql56m1
echo "export PATH=$PATH:/usr/local/mysql56m1/bin">>/etc/profile 
source /etc/profile
chkconfig --add mysql56m1

service mysql56m1 start

3， 准备备库

tar -xvf mysql-5.6.12.tar.gz
cd mysql-5.6.12

time cmake . -DCMAKE_INSTALL_PREFIX=/usr/local/mysql56s1 -DMYSQL_DATADIR=/home/data/mysql56s1/data -DWITH_INNOBASE_STORAGE_ENGINE=1 -DMYSQL_UNIX_ADDR==/usr/local/mysql56s1/mysql.sock -DMYSQL_USER=mysql -DDEFAULT_CHARSET=utf8 -DDEFAULT_COLLATION=utf8_general_ci

time make
time make install 


 chown -R mysql /home/data/
 chgrp -R mysql /home/data/
 chown -R mysql /usr/local/mysql

 chown -R mysql /usr/local/mysql56s1
 chgrp -R mysql /usr/local/mysql

 chgrp -R mysql /usr/local/mysql56s1/
 mkdir -p /home/data/mysql56s1/binlog/
 chown -R mysql.mysql /home/data/mysql56s1/binlog/
 mkdir -p /home/data/mysql5610/binlog/
 chown -R mysql.mysql /home/data/


cd /usr/local/mysql56s1
time scripts/mysql_install_db  --user=mysql --basedir=/usr/local/mysql56s1 --datadir=/home/data/mysql56s1/data --defaults-file=/usr/local/mysql56s1/my.cnf

cp support-files/mysql.server /etc/init.d/mysql56s1
chmod 700 /etc/init.d/mysql56s1
echo "export PATH=$PATH:/usr/local/mysql56s1/bin">>/etc/profile 
source /etc/profile
chkconfig --add mysql56s1
service mysql56s1 start

4， 搭建主从环境

在一台服务器，主3317端口，从3327端口。
主库备库上，添加复制帐号：

GRANT REPLICATION SLAVE ON . TO ‘repl’@’10.254.%’ IDENTIFIED BY ‘mycatms’;

在备库上3327端口上设置复制：

stop slave;
reset slave;
change master to master_user='repl', master_password='mycatms', master_host='127.0.0.1',master_port=3317, master_log_file='mysql-bin.000003',master_log_pos=840;
start slave;
show slave status\G;

主库：3317端口

从库：3327端口

数据同步测试：

5， 数据同步测试：

配置schema.xml：
然后修改mycat的schema.xml：
balance为1：让全部的readHost及备用的writeHost参与select的负载均衡。
switchType为2：基于MySQL主从同步的状态决定是否切换。
heartbeat：主从切换的心跳语句必须为show slave status。

5.0 数据录入：

mysql> explain create table company(id int not null primary key,name varchar(100)); +-----------+---------------------------------------------------------------------+
| DATA_NODE | SQL | +-----------+---------------------------------------------------------------------+
| dn1       | create table company(id int not null primary key,name varchar(100)) |
| dn2       | create table company(id int not null primary key,name varchar(100)) |
| dn3 | create table company(id int not null primary key,name varchar(100)) | +-----------+---------------------------------------------------------------------+
3 rows in set (0.00 sec)

mysql> create table company(id int not null primary key,name varchar(100));
Query OK, 0 rows affected (0.01 sec)

mysql> explain insert into company(id,name) values(1,'alibaba'); +-----------+--------------------------------------------------+
| DATA_NODE | SQL | +-----------+--------------------------------------------------+
| dn1       | insert into company(id,name) values(1,'alibaba') |
| dn2       | insert into company(id,name) values(1,'alibaba') |
| dn3 | insert into company(id,name) values(1,'alibaba') | +-----------+--------------------------------------------------+
3 rows in set (0.10 sec)

mysql>  insert into company(id,name) values(1,'alibaba');
Query OK, 1 row affected (0.00 sec)

mysql>

5.1主库验证：

[root@wgq_idc_squid_1_11 logs]# /usr/local/mysql56m1/bin/mysql -uroot -p -P3317 --socket=/usr/local/mysql56m1/mysql.sock -e "select @@port;select * from db1.company";
Enter password: +--------+
| @@port | +--------+
| 3317 | +--------+
+----+---------+
| id | name | +----+---------+
| 1 | alibaba | +----+---------+
[root@wgq_idc_squid_1_11 logs]#

5.2从库验证：

[root@wgq_idc_squid_1_11 logs]# /usr/local/mysql56s1/bin/mysql -uroot -p -P3327 --socket=/usr/local/mysql56s1/mysql.sock -e "select @@port;select * from db1.company";
Enter password: +--------+
| @@port | +--------+
| 3327 | +--------+
+----+---------+
| id | name | +----+---------+
| 1 | alibaba | +----+---------+
[root@wgq_idc_squid_1_11 logs]#

6，读写分离模式

6.1然后修改mycat的schema.xml：

balance为1：让全部的readHost及备用的writeHost参与select的负载均衡。
switchType为2：基于MySQL主从同步的状态决定是否切换。
heartbeat：主从切换的心跳语句必须为show slave status。

有配置读节点：

6.2 打开debug模式

[root@wgq_idc_squid_1_11 conf]# vim log4j.xml
<level value="info" /> 变成  <level value="debug" />

6.3 执行查询读操作

在mycat窗口上执行select操作：

mysql> explain select * from company where id=1; +-----------+----------------------------------------------+
| DATA_NODE | SQL | +-----------+----------------------------------------------+
| dn3 | SELECT * FROM company WHERE id = 1 LIMIT 100 | +-----------+----------------------------------------------+
1 row in set (0.14 sec)

mysql> select * from company where id=1; +----+---------+
| id | name | +----+---------+
| 1 | alibaba | +----+---------+
1 row in set (0.01 sec)

mysql>

后台日志显示出只在3327上执行：

01/18 01:35:01.536  DEBUG [$_NIOREACTOR-3-RW] (PhysicalDBPool.java:452) -select read source hostS2 for dataHost:wgq_idc_mon_1_11 01/18 01:35:01.537 DEBUG [$_NIOREACTOR-3-RW] (MySQLConnection.java:445) -con need syn ,total syn cmd 2 commands SET names latin1;SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ;schema change:false con:MySQLConnection [id=14, lastTime=1453052101537, user=root, schema=db1, old shema=db1, borrowed=true, fromSlaveDB=false, threadId=3326, charset=latin1, txIsolation=0, autocommit=true, attachment=dn1{SELECT * FROM company WHERE id = 1 LIMIT 100}, respHandler=SingleNodeHandler [node=dn1{SELECT * FROM company WHERE id = 1 LIMIT 100}, packetId=0], host=127.0.0.1, port=3327, statusSync=null, writeQueue=0, modifiedSQLExecuted=false] 01/18 01:35:01.546 DEBUG [$_NIOREACTOR-2-RW] (NonBlockingSession.java:229) -release connection MySQLConnection [id=14, lastTime=1453052101529, user=root, schema=db1, old shema=db1, borrowed=true, fromSlaveDB=false, threadId=3326, charset=latin1, txIsolation=3, autocommit=true, attachment=dn1{SELECT * FROM company WHERE id = 1 LIMIT 100}, respHandler=SingleNodeHandler [node=dn1{SELECT * FROM company WHERE id = 1 LIMIT 100}, packetId=5], host=127.0.0.1, port=3327, statusSync=org.opencloudb.mysql.nio.MySQLConnection$StatusSync@7fb43f0f, writeQueue=0, modifiedSQLExecuted=false] 01/18 01:35:01.547 DEBUG [$_NIOREACTOR-2-RW] (PhysicalDatasource.java:403) -release channel MySQLConnection [id=14, lastTime=1453052101529, user=root, schema=db1, old shema=db1, borrowed=true, fromSlaveDB=false, threadId=3326, charset=latin1, txIsolation=3, autocommit=true, attachment=null, respHandler=null, host=127.0.0.1, port=3327, statusSync=null, writeQueue=0, modifiedSQLExecuted=false] ^C

6.4 执行写操作

Mycat窗口写操作：

后台log显示写操作在3317上：

01/18 01:39:54.550  DEBUG [$_NIOREACTOR-3-RW] (NonBlockingSession.java:229) -release connection MySQLConnection [id=7, lastTime=1453052394535, user=root, schema=db3, old shema=db3, borrowed=true, fromSlaveDB=false, threadId=163, charset=latin1, txIsolation=3, autocommit=true, attachment=dn3{insert into company values(3,'baidu')}, respHandler=org.opencloudb.mysql.nio.handler.MultiNodeQueryHandler@42bed1e7, host=127.0.0.1, port=3317, statusSync=null, writeQueue=0, modifiedSQLExecuted=true] 01/18 01:39:54.550 DEBUG [$_NIOREACTOR-3-RW] (PhysicalDatasource.java:403) -release channel MySQLConnection [id=7, lastTime=1453052394535, user=root, schema=db3, old shema=db3, borrowed=true, fromSlaveDB=false, threadId=163, charset=latin1, txIsolation=3, autocommit=true, attachment=null, respHandler=null, host=127.0.0.1, port=3317, statusSync=null, writeQueue=0, modifiedSQLExecuted=false] 01/18 01:39:54.550 DEBUG [$_NIOREACTOR-3-RW] (MultiNodeQueryHandler.java:171) -received ok response ,executeResponse:true from MySQLConnection [id=3, lastTime=1453052394535, user=root, schema=db2, old shema=db2, borrowed=true, fromSlaveDB=false, threadId=162, charset=latin1, txIsolation=3, autocommit=true, attachment=dn2{insert into company values(3,'baidu')}, respHandler=org.opencloudb.mysql.nio.handler.MultiNodeQueryHandler@42bed1e7, host=127.0.0.1, port=3317, statusSync=null, writeQueue=0, modifiedSQLExecuted=true] 01/18 01:39:54.551 DEBUG [$_NIOREACTOR-3-RW] (NonBlockingSession.java:229) -release connection MySQLConnection [id=3, lastTime=1453052394535, user=root, schema=db2, old shema=db2, borrowed=true, fromSlaveDB=false, threadId=162, charset=latin1, txIsolation=3, autocommit=true, attachment=dn2{insert into company values(3,'baidu')}, respHandler=org.opencloudb.mysql.nio.handler.MultiNodeQueryHandler@42bed1e7, host=127.0.0.1, port=3317, statusSync=null, writeQueue=0, modifiedSQLExecuted=true] 01/18 01:39:54.551 DEBUG [$_NIOREACTOR-3-RW] (PhysicalDatasource.java:403) -release channel MySQLConnection [id=3, lastTime=1453052394535, user=root, schema=db2, old shema=db2, borrowed=true, fromSlaveDB=false, threadId=162, charset=latin1, txIsolation=3, autocommit=true, attachment=null, respHandler=null, host=127.0.0.1, port=3317, statusSync=null, writeQueue=0, modifiedSQLExecuted=false]

Check下主从数据是否都已经写入了：
主库3317端口：

从裤3327端口：

7，主从切换测试

7.1 mycat托管配置如下

     <dataHost name="wgq_idc_mon_1_11" maxCon="1000" minCon="10" balance="1" writeType="0" dbType="mysql" dbDriver="native" switchType="2" slaveThreshold="100">
                <heartbeat>show slave status</heartbeat>
                <!-- can have multi write hosts -->
                <writeHost host="hostM1" url="127.0.0.1:3317" user="root" password="">
                        <readHost host="hostR1" url="127.0.0.1:3327" user="root" password=""/>
                </writeHost>
                <writeHost host="hostS2" url="127.0.0.1:3327" user="root" password="" />
        </dataHost>

7.2 关闭主库，写操作切换到从裤3327端口

关闭主库

[root@wgq_idc_squid_1_11 conf]# service mysql56m1 stop
Shutting down MySQL....                                    [确定]
[root@wgq_idc_squid_1_11 conf]#

Mycat后台报错：

01/18 01:50:01.037   INFO [Timer0] (PhysicalDatasource.java:373) -not ilde connection in pool,create new connection for hostM1 of schema db1 01/18 01:50:01.038 INFO [$_NIOConnector] (AbstractConnection.java:458) -close connection,reason:java.net.ConnectException: 拒绝连接 ,MySQLConnection [id=0, lastTime=1453053001035, user=root, schema=db1, old shema=db1, borrowed=false, fromSlaveDB=false, threadId=0, charset=utf8, txIsolation=0, autocommit=true, attachment=null, respHandler=null, host=127.0.0.1, port=3317, statusSync=null, writeQueue=0, modifiedSQLExecuted=false] 01/18 01:50:01.038 INFO [$_NIOConnector] (SQLJob.java:111) -can't get connection for sql :show slave status 01/18 01:50:01.038 WARN [$_NIOREACTOR-1-RW] (MySQLDetector.java:139) -found MySQL master/slave Replication err !!! DBHostConfig [hostName=hostR1, url=127.0.0.1:3327]error reconnecting to master 'repl@127.0.0.1:3317' - retry-time: 60 retries: 1 0

看到主从失效，因为主down了。

因为我们通过mycat配置了主从切换模式，现在3317端口主库down了，那么写库应该自动切换到从裤3327上面，如果在mycat上面写入，就应该写到3327端口的从库了，验证如下：
（1）在mycat窗口录入数据：

（2）在3327端口从裤验证数据：

看到3327端口的数据有新录入的4,meituan的数据。表明验证成功。
(3) dnindex属性文件中writeHost已经变成了第二个了，如下所示：

7.3 再启动原来的主库3317端口，在mycat上做写操作，后台mysql写库还是原来的从库3327端口：

这个时候就会报错，主从连接失败，原因是从库3327会再重新从主库3317同步所有的数据，但是从库已经有了，所以就会报错，如下所示：

我采用

stop slave;
 set global sql_slave_skip_counter=1;
 start slave;
 show slave status\G;

一个个忽略过后，就正常了，没有报错：

但是这个时候如果再在mycat窗口上录入数据，debug分析面，还是会写入到3327里面去：

后台debug日志：

OK，至此，mycat主从切换成功。