一 环境
1.1 结构
192.168.132.125 mycat
192.168.132.121 master
192.168.132.122 slave
主从已经配置完成
1.2 安装mycat
192.168.132.125安装mycat
[root@mycat ~]# cd /usr/local/src/
[root@mycat src]# wget http://dl.mycat.io/1.6-RELEASE/Mycat-server-1.6-RELEASE-20161028204710-linux.tar.gz
[root@mycat src]# tar -xf Mycat-server-1.6-RELEASE-20161028204710-linux.tar.gz
[root@mycat src]# cd mycat/
[root@mycat mycat]# ll
drwxr-xr-x. 2 root root 190 Jul 12 08:50 bin
drwxrwxrwx. 2 root root 6 Feb 29 2016 catlet
drwxrwxrwx. 4 root root 4096 Jul 12 08:50 conf
drwxr-xr-x. 2 root root 4096 Jul 12 08:50 lib
drwxrwxrwx. 2 root root 6 Oct 28 2016 logs
-rwxrwxrwx. 1 root root 217 Oct 28 2016 version.txt
1.3 配置mycat
[root@mycat mycat]# cd conf/
[root@mycat conf]# ll
-rwxrwxrwx. 1 root root 88 Oct 28 2016 autopartition-long.txt
-rwxrwxrwx. 1 root root 48 Oct 28 2016 auto-sharding-long.txt
-rwxrwxrwx. 1 root root 62 Oct 28 2016 auto-sharding-rang-mod.txt
-rwxrwxrwx. 1 root root 334 Oct 28 2016 cacheservice.properties
-rwxrwxrwx. 1 root root 439 Oct 28 2016 ehcache.xml
-rwxrwxrwx. 1 root root 2132 Oct 28 2016 index_to_charset.properties
-rwxrwxrwx. 1 root root 1246 Oct 10 2016 log4j2.xml
-rwxrwxrwx. 1 root root 178 Oct 28 2016 migrateTables.properties
-rwxrwxrwx. 1 root root 246 Oct 28 2016 myid.properties
-rwxrwxrwx. 1 root root 15 Oct 28 2016 partition-hash-int.txt
-rwxrwxrwx. 1 root root 102 Oct 28 2016 partition-range-mod.txt
-rwxrwxrwx. 1 root root 4794 Oct 28 2016 rule.xml
-rwxrwxrwx. 1 root root 4219 Oct 28 2016 schema.xml #主要配置这个文件
-rwxrwxrwx. 1 root root 413 Oct 28 2016 sequence_conf.properties
-rwxrwxrwx. 1 root root 75 Oct 28 2016 sequence_db_conf.properties
-rwxrwxrwx. 1 root root 27 Oct 28 2016 sequence_distributed_conf.properties
-rwxrwxrwx. 1 root root 51 Oct 28 2016 sequence_time_conf.properties
-rwxrwxrwx. 1 root root 3717 Oct 28 2016 server.xml
-rwxrwxrwx. 1 root root 16 Oct 28 2016 sharding-by-enum.txt
-rwxrwxrwx. 1 root root 4182 Oct 28 2016 wrapper.conf
drwxrwxrwx. 2 root root 4096 Jul 12 08:50 zkconf
drwxrwxrwx. 2 root root 36 Jul 12 08:50 zkdownload
[root@mycat conf]# cat schema.xml
<?xml version="1.0"?>
<!DOCTYPE mycat:schema SYSTEM "schema.dtd">
<mycat:schema xmlns:mycat="http://io.mycat/">
<!‐‐ TESTDB 表示mycat 的逻辑数据库名称当schema 节点没有子节点table 的时候，一定要有dataNode 属性存在‐‐>
<schema name="TESTDB" checkSQLschema="false" sqlMaxLimit="100" dataNode="dn1">
</schema>
<dataNode name="dn1" dataHost="localhost1" database="master1" />
<dataHost name="localhost1" maxCon="1000" minCon="10" balance="3"
writeType="0" dbType="mysql" dbDriver="native" switchType="1" slaveThreshold="100">
<heartbeat>select user()</heartbeat>
<!-- can have multi write hosts -->
<writeHost host="hostM1" url="192.168.132.121:3306" user="root"
password="123456">
<!-- can have multi read hosts -->
<readHost host="hostS2" url="192.168.132.122:3306" user="root" password="123456" />
</writeHost>
</dataHost>
</mycat:schema>
注意 dataHost 节点的下面三个属性balance， switchType， writeType
balance="0", 不开启读写分离机制，所有读操作都发送到当前可用的writeHost 上。
balance="1"，全部的readHost 与stand by writeHost 参与select语句的负载均衡，简单的说，当双主双从模式(M1‐>S1，M2‐>S2，并且M1 与M2 互为主备)，正常情况下，M2,S1,S2都参与select 语句的负载均衡。
balance="2"，所有读操作都随机的在writeHost、readhost 上分发。
balance="3"，所有读请求随机的分发到writeHost 下的readhost 执行，writeHost 不负担读压力
writeType 表示写模式
writeType="0"，所有的操作发送到配置的第一个writehost
writeType="1"，随机发送到配置的所有writehost
writeType="2"，不执行写操作
switchType 指的是切换的模式，目前的取值也有4 种：
switchType=‘‐1‘ 表示不自动切换
switchType=‘1‘ 默认值，表示自动切换
switchType=‘2‘ 基于MySQL 主从同步的状态决定是否切换,心跳语句为show slave status
switchType=‘3‘基于MySQL galary cluster 的切换机制（适合集群）（1.4.1），心跳语句为show status like ‘wsrep%‘。
配置端口，用户名
[root@mycat conf]# vim server.xml
<?xml version="1.0" encoding="UTF-8"?>
<!-- - - Licensed under the Apache License, Version 2.0 (the "License");
- you may not use this file except in compliance with the License. - You
may obtain a copy of the License at - - http://www.apache.org/licenses/LICENSE-2.0
- - Unless required by applicable law or agreed to in writing, software -
distributed under the License is distributed on an "AS IS" BASIS, - WITHOUT
WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. - See the
License for the specific language governing permissions and - limitations
under the License. -->
<!DOCTYPE mycat:server SYSTEM "server.dtd">
<mycat:server xmlns:mycat="http://io.mycat/">
<system>
<property name="useSqlStat">0</property> <!-- 1为开启实时统计、0为关闭 -->
<property name="useGlobleTableCheck">0</property> <!-- 1为开启全加班一致性检测、0为关闭 -->
<property name="sequnceHandlerType">2</property>
<!-- <property name="useCompression">1</property>--> <!--1为开启mysql压缩协议-->
<!-- <property name="fakeMySQLVersion">5.6.20</property>--> <!--设置模拟的MySQL版本号-->
<!-- <property name="processorBufferChunk">40960</property> -->
<!--
<property name="processors">1</property>
<property name="processorExecutor">32</property>
-->
<!--默认为type 0: DirectByteBufferPool | type 1 ByteBufferArena-->
<property name="processorBufferPoolType">0</property>
<!--默认是65535 64K 用于sql解析时最大文本长度 -->
<!--<property name="maxStringLiteralLength">65535</property>-->
<!--<property name="sequnceHandlerType">0</property>-->
<!--<property name="backSocketNoDelay">1</property>-->
<!--<property name="frontSocketNoDelay">1</property>-->
<!--<property name="processorExecutor">16</property>-->
<!--
<property name="handleDistributedTransactions">0</property>
<!-- off heap for merge/order/group/limit 1开启 0关闭 -->
<property name="useOffHeapForMerge">1</property>
<!-- 单位为m -->
<property name="memoryPageSize">1m</property>
<!-- 单位为k -->
<property name="spillsFileBufferSize">1k</property>
<property name="useStreamOutput">0</property>
<!-- 单位为m -->
<property name="systemReserveMemorySize">384m</property>
<!--是否采用zookeeper协调切换 -->
<property name="useZKSwitch">true</property>
</system>
<!-- 全局SQL防火墙设置 -->
<!--
<firewall>
<whitehost>
<host host="127.0.0.1" user="mycat"/>
<host host="127.0.0.2" user="mycat"/>
</whitehost>
<blacklist check="false">
</blacklist>
</firewall>
-->
<user name="root">
<property name="password">123456</property>
<property name="schemas">TESTDB</property>
<!-- 表级 DML 权限设置 -->
<!--
<privileges check="false">
<schema name="TESTDB" dml="0110" >
<table name="tb01" dml="0000"></table>
<table name="tb02" dml="1111"></table>
</schema>
</privileges>
-->
</user>
<user name="user">
<property name="password">user</property>
<property name="schemas">TESTDB</property>
<property name="readOnly">true</property>
</user>
</mycat:server
二 验证
2.1 启动Mycat
[root@mycat conf]# ../bin/mycat start
2.2 日志
[root@mycat conf]# cat /usr/local/src/mycat/logs/wrapper.log
STATUS | wrapper | 2019/07/12 10:44:55 | --> Wrapper Started as Daemon
STATUS | wrapper | 2019/07/12 10:44:55 | Launching a JVM...
ERROR | wrapper | 2019/07/12 10:45:12 | Unable to start JVM: No such file or directory (2) #没有JVM，安装java
ERROR | wrapper | 2019/07/12 10:45:12 | JVM exited while loading the application.
FATAL | wrapper | 2019/07/12 10:45:12 | There were 5 failed launches in a row, each lasting less than 300 seconds. Giving up.
FATAL | wrapper | 2019/07/12 10:45:12 | There may be a configuration problem: please check the logs.
STATUS | wrapper | 2019/07/12 10:45:12 | <-- Wrapper Stopped
[root@mycat conf]# yum -y install java
[root@mycat conf]# ../bin/mycat start
[root@mycat conf]# tail -f /usr/local/src/mycat/logs/wrapper.log
INFO | jvm 1 | 2019/07/12 11:02:46 | 2019-07-12 11:02:46,389 [INFO ][$_NIOREACTOR-0-RW] connectionAcquired MySQLConnection [id=12, lastTime=1562943766373, user=root, schema=master1, old shema=master1, borrowed=false, fromSlaveDB=true, threadId=1428, charset=latin1, txIsolation=3, autocommit=true, attachment=null, respHandler=null, host=192.168.132.122, port=3306, statusSync=null, writeQueue=0, modifiedSQLExecuted=false] (io.mycat.backend.mysql.nio.handler.NewConnectionRespHandler:NewConnectionRespHandler.java:45)
INFO | jvm 1 | 2019/07/12 11:02:46 | MyCAT Server startup successfully. see logs in logs/mycat.log
2.3 连接，端口为8066
[root@mycat ~]# mysql -uroot -p1234567 -h192.168.132.125 -P8066
MySQL [(none)]> show databases;
+----------+
| DATABASE |
+----------+
| TESTDB |
+----------+
2.4 写入数据测试
MySQL [(none)]> use TESTDB;
MySQL [TESTDB]> show tables;
MySQL [TESTDB]> select * from test;
MySQL [TESTDB]> insert into test values (555);
MySQL [TESTDB]> select * from test;
+------+
| id |
+------+
| 1 |
| 2 |
| 2 |
| 2 |
| 11 |
| 12 |
| 111 |
| 222 |
| 333 |
| 444 |
| 555 |
+------+
mater查看
mysql> select * from master1.test;
+------+
| id |
+------+
| 1 |
| 2 |
| 2 |
| 2 |
| 11 |
| 12 |
| 111 |
| 222 |
| 333 |
| 444 |
| 555 |
+------+
slave查看
mysql> select * from master1.test;
+------+
| id |
+------+
| 1 |
| 2 |
| 2 |
| 2 |
| 11 |
| 12 |
| 111 |
| 222 |
| 333 |
| 444 |
| 555 |
+------+
成功写入数据
2.5 验证读写分离
修改日志级别为debug
[root@mycat conf]# vim log4j2.xml
<Loggers>
<!--<AsyncLogger name="io.mycat" level="info" includeLocation="true" additivity="false">-->
<!--<AppenderRef ref="Console"/>-->
<!--<AppenderRef ref="RollingFile"/>-->
<!--</AsyncLogger>-->
<asyncRoot level="debug" includeLocation="true">
<AppenderRef ref="Console" />
<AppenderRef ref="RollingFile"/>
</asyncRoot>
</Loggers>
[root@mycat conf]# /usr/local/src/mycat/bin/mycat stop
[root@mycat conf]# /usr/local/src/mycat/bin/mycat start
写入一个数据
MySQL [TESTDB]> insert into test values (666);
[root@mycat conf]# tail -f /usr/local/src/mycat/logs/wrapper.log
INFO | jvm 1 | 2019/07/12 11:15:06 | 2019-07-12 11:15:06,662 [DEBUG][$_NIOREACTOR-0-RW] con need syn ,total syn cmd 1 commands SET names utf8;schema change:false con:MySQLConnection [id=7, lastTime=1562944506662, user=root, schema=master1, old shema=master1, borrowed=true, fromSlaveDB=false, threadId=14906, charset=utf8, txIsolation=3, autocommit=true, attachment=dn1{insert into test values (666)}, respHandler=SingleNodeHandler [node=dn1{insert into test values (666)}, packetId=0], host=192.168.132.121, port=3306, statusSync=null, writeQueue=0, modifiedSQLExecuted=true] (io.mycat.backend.mysql.nio.MySQLConnection:MySQLConnection.java:448)
INFO | jvm 1 | 2019/07/12 11:15:06 | 2019-07-12 11:15:06,668 [DEBUG][$_NIOREACTOR-1-RW] release connection MySQLConnection [id=7, lastTime=1562944506646, user=root, schema=master1, old shema=master1, borrowed=true, fromSlaveDB=false, threadId=14906, charset=utf8, txIsolation=3, autocommit=true, attachment=dn1{insert into test values (666)}, respHandler=SingleNodeHandler [node=dn1{insert into test values (666)}, packetId=1], host=192.168.132.121, port=3306, statusSync=null, writeQueue=0, modifiedSQLExecuted=true] (io.mycat.server.NonBlockingSession:NonBlockingSession.java:341)
INFO | jvm 1 | 2019/07/12 11:15:06 | 2019-07-12 11:15:06,669 [DEBUG][$_NIOREACTOR-1-RW] release channel MySQLConnection [id=7, lastTime=1562944506646, user=root, schema=master1, old shema=master1, borrowed=true, fromSlaveDB=false, threadId=14906, charset=utf8, txIsolation=3, autocommit=true, attachment=null, respHandler=null, host=192.168.132.121, port=3306, statusSync=null, writeQueue=0, modifiedSQLExecuted=false] (io.mycat.backend.datasource.PhysicalDatasource:PhysicalDatasource.java:442)
INFO | jvm 1 | 2019/07/12 11:15:14 | 2019-07-12 11:15:13,968 [DEBUG][Timer1] con query sql:select user() to con:MySQLConnection [id=3, lastTime=1562944513968, user=root, schema=master1, old shema=master1, borrowed=true, fromSlaveDB=false, threadId=14907, charset=latin1, txIsolation=3, autocommit=true, attachment=null, respHandler=null, host=192.168.132.121, port=3306, statusSync=null, writeQueue=0, modifiedSQLExecuted=false] (io.mycat.sqlengine.SQLJob:SQLJob.java:88)
发现在192.168.132.121 主数据库上面
查找数据
MySQL [TESTDB]> select * from test;
INFO | jvm 1 | 2019/07/12 11:20:13 | 2019-07-12 11:20:13,419 [DEBUG][$_NIOREACTOR-0-RW] con need syn ,total syn cmd 1 commands SET names utf8;schema change:false con:MySQLConnection [id=15, lastTime=1562944813419, user=root, schema=master1, old shema=master1, borrowed=true, fromSlaveDB=true, threadId=1596, charset=utf8, txIsolation=3, autocommit=true, attachment=dn1{select * from test}, respHandler=SingleNodeHandler [node=dn1{select * from test}, packetId=0], host=192.168.132.122, port=3306, statusSync=null, writeQueue=0, modifiedSQLExecuted=false] (io.mycat.backend.mysql.nio.MySQLConnection:MySQLConnection.java:448)
INFO | jvm 1 | 2019/07/12 11:20:13 | 2019-07-12 11:20:13,421 [DEBUG][$_NIOREACTOR-0-RW] release connection MySQLConnection [id=15, lastTime=1562944813407, user=root, schema=master1, old shema=master1, borrowed=true, fromSlaveDB=true, threadId=1596, charset=utf8, txIsolation=3, autocommit=true, attachment=dn1{select * from test}, respHandler=SingleNodeHandler [node=dn1{select * from test}, packetId=16], host=192.168.132.122, port=3306, statusSync=io.mycat.backend.mysql.nio.MySQLConnection$StatusSync@3055d901, writeQueue=0, modifiedSQLExecuted=false] (io.mycat.server.NonBlockingSession:NonBlockingSession.java:341)
在salve192.168.132.122从数据库上面，读和写在不同的服务器上面
2.6 问题
但这种方式有个问题，即master 挂了以后，slave 也不能提供读和写服务Slave 挂了 不能查询，但是可以插入。
停掉主数据库
[root@master1 ~]# systemctl stop mysqld
[root@mycat ~]# mysql -uroot -p1234567 -h192.168.132.125 -P8066 TESTDB
MySQL [TESTDB]> select * from test;
ERROR 1184 (HY000): Connection refused
MySQL [TESTDB]> insert into test values (777);
ERROR 1184 (HY000): Connection refused
已经不能查询，也不可以插入
停掉slave
不可以查，但是可以写
[root@slave ~]# systemctl stop mysqld
MySQL [TESTDB]> select * from test;
ERROR 1184 (HY000): Connection refused
MySQL [TESTDB]> insert into test values (777);
Query OK, 1 row affected (0.00 sec)
读写分离配置完成
这种结构过于简单，但是实现了读写分离的功能，生产中需要综合考虑单点故障的问题，需要更可靠的架构！
