一：mysql读写分离原理
MySQL的主从复制和MySQL的读写分离两者有着紧密联系，首先部署主从复制，只有主从复制完了，才能在此基础上进行数据的读写分离。
简单来说，读写分离就是只在主服务器上写，只在从服务器上读，基本的原理是让主数据库处理事务性操作，而从数据库处理非事务性操作，然后再采用主从复制来把master上的事务性操作同步到slave数据库中。
1.基于程序代码内部实现
在代码中根据select,insert进行路由分类，这类方法也是目前生产环境应用最广泛的，优点是性能好，因为在程序代码中实现，不需要曾加额外的设备作为硬件开支，缺点是需要开发人员来实现，运维人员无从下手。
2.基于中间代理层实现
代理一般位于客户端和服务器之间，代理服务器接到客户端请求后通过判断后转发到后端数据库，有两个代表性程序。
（1）mysql-proxy 为mysql开源项目，通过其自带的lua脚本进行SQL判断，虽然是mysql的官方产品，但是mysql官方不建议将其应用到生产环境
（2）Amoeba （变形虫）由陈思儒开发，曾就职与阿里巴巴，该程序由java语言进行开发，阿里巴巴将其应用于生成环境，它不支持事物和存储过程
通过程序代码实现mysql读写分离自然是一个不错的选择，但是并不是所有的应用都适合在程序代码中实现读写分离，像一些大型复杂的java应用，如果在程序代码中实现读写分离对代码改动就较大，像这种应用一般会考虑使用代理层来实现。
二：基于 Amoeba 实现读写分离
2.1 环境搭建
amoeba:192.168.2.203
masterDB：192.168.2.204
slaveDB：192.168.2.205
以上系统全为centos6.8
Amoeba框架是居于JDK1.5开发的，采用了JDK1.5的特性，所以还需要安装java环境，建议使用javaSE1.5以上的JDK版本
2.2 安装java环境
先去官网下载：http://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html
2.2.1 安装
[root@bogon src]# rpm -ivh jdk-8u111-linux-x64.rpm
Preparing... ########################################### [100%]
1:jdk1.8.0_111 ########################################### [100%]
Unpacking JAR files...
tools.jar...
plugin.jar...
javaws.jar...
deploy.jar...
rt.jar...
jsse.jar...
charsets.jar...
localedata.jar...
2.2.2 设置java环境变量
[root@bogon src]# vim /etc/profile
#set java environment
JAVA_HOME=/usr/java/jdk1.8.0_111
JRE_HOME=/usr/java/jdk1.8.0_111/jre
CLASS_PATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar:$JRE_HOME/lib
PATH=$PATH:$JAVA_HOME/bin:$JRE_HOME/bin
export JAVA_HOME JRE_HOME CLASS_PATH PATH
[root@bogon amoeba]# source /etc/profile
2.2.3 测试是否安装成功
[root@bogon src]# java -version
java version "1.8.0_111"
Java(TM) SE Runtime Environment (build 1.8.0_111-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.111-b14, mixed mode)
2.3 安装Amoeba
可以从https://sourceforge.net/projects/amoeba/下载最新版本的Amoeba，我这里下载的是amoeba-mysql-3.0.5-RC-distribution.zip。Amoeba安装非常简单，直接解压即可使用，这里将Amoeba解压到/usr/local/amoeba目录下，这样就安装完成了
[root@bogon amoeba]# pwd
/usr/local/amoeba
[root@bogon amoeba]# ll
总用量 20
drwxrwxrwx. 2 root root 4096 7月 5 2013 benchmark
drwxrwxrwx. 2 root root 4096 7月 5 2013 bin
drwxrwxrwx. 2 root root 4096 7月 5 2013 conf
-rwxrwxrwx. 1 root root 728 7月 5 2013 jvm.properties
drwxrwxrwx. 2 root root 4096 7月 5 2013 lib
2.4 配置Amoeba
Amoeba的配置文件在本环境下位于/usr/local/amoeba/conf目录下。配置文件比较多，但是仅仅使用读写分离功能，只需配置两个文件即可，分别是dbServers.xml和amoeba.xml，如果需要配置ip访问控制，还需要修改access_list.conf文件，下面首先介绍dbServers.xml
[root@bogon amoeba]# cat conf/dbServers.xml
<?xml version="1.0" encoding="gbk"?>
<!DOCTYPE amoeba:dbServers SYSTEM "dbserver.dtd">
<amoeba:dbServers xmlns:amoeba="http://amoeba.meidusa.com/">
<!--
Each dbServer needs to be configured into a Pool,
If you need to configure multiple dbServer with load balancing that can be simplified by the following configuration:
add attribute with name virtual = "true" in dbServer, but the configuration does not allow the element with name factoryConfig
such as 'multiPool' dbServer
-->
<dbServer name="abstractServer" abstractive="true">
<factoryConfig class="com.meidusa.amoeba.mysql.net.MysqlServerConnectionFactory">
<property name="connectionManager">${defaultManager}</property>
<property name="sendBufferSize">64</property>
<property name="receiveBufferSize">128</property>
<!-- mysql port -->
<property name="port">3306</property> #设置Amoeba要连接的mysql数据库的端口，默认是3306
<!-- mysql schema -->
<property name="schema">testdb</property> #设置缺省的数据库，当连接amoeba时，操作表必须显式的指定数据库名，即采用dbname.tablename的方式，不支持 use dbname指定缺省库，因为操作会调度到各个后端dbserver
<!-- mysql user -->
<property name="user">test1</property> #设置amoeba连接后端数据库服务器的账号和密码，因此需要在所有后端数据库上创建该用户，并授权amoeba服务器可连接
<property name="password">111111</property>
</factoryConfig>
<poolConfig class="com.meidusa.toolkit.common.poolable.PoolableObjectPool">
<property name="maxActive">500</property> #最大连接数，默认500
<property name="maxIdle">500</property> #最大空闲连接数
<property name="minIdle">1</property> #最新空闲连接数
<property name="minEvictableIdleTimeMillis">600000</property>
<property name="timeBetweenEvictionRunsMillis">600000</property>
<property name="testOnBorrow">true</property>
<property name="testOnReturn">true</property>
<property name="testWhileIdle">true</property>
</poolConfig>
</dbServer>
<dbServer name="writedb" parent="abstractServer"> #设置一个后端可写的dbServer，这里定义为writedb，这个名字可以任意命名，后面还会用到
<factoryConfig>
<!-- mysql ip -->
<property name="ipAddress">192.168.2.204</property> #设置后端可写dbserver
</factoryConfig>
</dbServer>
<dbServer name="slave" parent="abstractServer"> #设置后端可读dbserver
<factoryConfig>
<!-- mysql ip -->
<property name="ipAddress">192.168.2.205</property>
</factoryConfig>
</dbServer>
<dbServer name="myslave" virtual="true"> #设置定义一个虚拟的dbserver，实际上相当于一个dbserver组，这里将可读的数据库ip统一放到一个组中，将这个组的名字命名为myslave
<poolConfig class="com.meidusa.amoeba.server.MultipleServerPool">
<!-- Load balancing strategy: 1=ROUNDROBIN , 2=WEIGHTBASED , 3=HA-->
<property name="loadbalance">1</property> #选择调度算法，1表示复制均衡，2表示权重，3表示HA， 这里选择1
<!-- Separated by commas,such as: server1,server2,server1 -->
<property name="poolNames">slave</property> #myslave组成员
</poolConfig>
</dbServer>
</amoeba:dbServers>
另一个配置文件amoeba.xml
[root@bogon amoeba]# cat conf/amoeba.xml
<?xml version="1.0" encoding="gbk"?>
<!DOCTYPE amoeba:configuration SYSTEM "amoeba.dtd">
<amoeba:configuration xmlns:amoeba="http://amoeba.meidusa.com/">
<proxy>
<!-- service class must implements com.meidusa.amoeba.service.Service -->
<service name="Amoeba for Mysql" class="com.meidusa.amoeba.mysql.server.MySQLService">
<!-- port -->
<property name="port">8066</property> #设置amoeba监听的端口，默认是8066
<!-- bind ipAddress --> #下面配置监听的接口，如果不设置，默认监听所以的IP
<!--
<property name="ipAddress">127.0.0.1</property>
-->
<property name="connectionFactory">
<bean class="com.meidusa.amoeba.mysql.net.MysqlClientConnectionFactory">
<property name="sendBufferSize">128</property>
<property name="receiveBufferSize">64</property>
</bean>
</property>
<property name="authenticateProvider">
<bean class="com.meidusa.amoeba.mysql.server.MysqlClientAuthenticator">
# 提供客户端连接amoeba时需要使用这里设定的账号 (这里的账号密码和amoeba连接后端数据库服务器的密码无关)
<property name="user">root</property>
<property name="password">123456</property>
<property name="filter">
<bean class="com.meidusa.toolkit.net.authenticate.server.IPAccessController">
<property name="ipFile">${amoeba.home}/conf/access_list.conf</property>
</bean>
</property>
</bean>
</property>
</service>
<runtime class="com.meidusa.amoeba.mysql.context.MysqlRuntimeContext">
<!-- proxy server client process thread size -->
<property name="executeThreadSize">128</property>
<!-- per connection cache prepared statement size -->
<property name="statementCacheSize">500</property>
<!-- default charset -->
<property name="serverCharset">utf8</property>
<!-- query timeout( default: 60 second , TimeUnit:second) -->
<property name="queryTimeout">60</property>
</runtime>
</proxy>
<!--
Each ConnectionManager will start as thread
manager responsible for the Connection IO read , Death Detection
-->
<connectionManagerList>
<connectionManager name="defaultManager" class="com.meidusa.toolkit.net.MultiConnectionManagerWrapper">
<property name="subManagerClassName">com.meidusa.toolkit.net.AuthingableConnectionManager</property>
</connectionManager>
</connectionManagerList>
<!-- default using file loader -->
<dbServerLoader class="com.meidusa.amoeba.context.DBServerConfigFileLoader">
<property name="configFile">${amoeba.home}/conf/dbServers.xml</property>
</dbServerLoader>
<queryRouter class="com.meidusa.amoeba.mysql.parser.MysqlQueryRouter">
<property name="ruleLoader">
<bean class="com.meidusa.amoeba.route.TableRuleFileLoader">
<property name="ruleFile">${amoeba.home}/conf/rule.xml</property>
<property name="functionFile">${amoeba.home}/conf/ruleFunctionMap.xml</property>
</bean>
</property>
<property name="sqlFunctionFile">${amoeba.home}/conf/functionMap.xml</property>
<property name="LRUMapSize">1500</property>
<property name="defaultPool">writedb</property> #设置amoeba默认的池，这里设置为writedb
<property name="writePool">writedb</property> #这两个选项默认是注销掉的，需要取消注释，这里用来指定前面定义好的俩个读写池
<property name="readPool">myslave</property> #
<property name="needParse">true</property>
</queryRouter>
</amoeba:configuration>
2.5 在masterdb上创建数据库testdb
mysql> create database testdb;
Query OK, 1 row affected (0.08 sec)
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mydb |
| mysql |
| performance_schema |
| test |
| testdb |
+--------------------+
6 rows in set (0.00 sec)
查看slavedb是否复制成功
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mydb |
| mysql |
| performance_schema |
| test |
| testdb |
+--------------------+
6 rows in set (0.00 sec)
分别在masterdb和slavedb上为amoedb授权
mysql> GRANT ALL ON testdb.* TO 'test1'@'192.168.2.203' IDENTIFIED BY '111111';
Query OK, 0 rows affected (0.05 sec)
mysql> flush privileges;
Query OK, 0 rows affected (0.02 sec)
启动amoeba
[root@bogon amoeba]# /usr/local/amoeba/bin/launcher
Error: JAVA_HOME environment variable is not set.
[root@bogon amoeba]# vim /etc/profile^C
[root@bogon amoeba]# source /etc/profile
[root@bogon amoeba]# /usr/local/amoeba/bin/launcher
Java HotSpot(TM) 64-Bit Server VM warning: ignoring option PermSize=16m; support was removed in 8.0
Java HotSpot(TM) 64-Bit Server VM warning: ignoring option MaxPermSize=96m; support was removed in 8.0
The stack size specified is too small, Specify at least 228k
Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit.
报错:
Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit.
从错误文字上看，应该是由于stack size太小，导致JVM启动失败，要如何修改呢？
其实Amoeba已经考虑到这个问题，并将JVM参数配置写在属性文件里。现在，让我们通过该属性文件修改JVM参数。
修改jvm.properties文件JVM_OPTIONS参数。
[root@bogon amoeba]# vim /usr/local/amoeba/jvm.properties
改成：JVM_OPTIONS="-server -Xms1024m -Xmx1024m -Xss256k -XX:PermSize=16m -XX:MaxPermSize=96m"
原为：JVM_OPTIONS="-server -Xms256m -Xmx1024m -Xss196k -XX:PermSize=16m -XX:MaxPermSize=96m"
再次启动
[root@bogon ~]# /usr/local/amoeba/bin/launcher
at org.codehaus.plexus.classworlds.launcher.Launcher.launchStandard(Launcher.java:329)
at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:239)
at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:409)
at org.codehaus.classworlds.Launcher.mainWithExitCode(Launcher.java:127)
at org.codehaus.classworlds.Launcher.main(Launcher.java:110)
Caused by: com.meidusa.toolkit.common.bean.util.InitialisationException: default pool required!,defaultPool=writedb invalid
at com.meidusa.amoeba.route.AbstractQueryRouter.init(AbstractQueryRouter.java:469)
at com.meidusa.amoeba.context.ProxyRuntimeContext.initAllInitialisableBeans(ProxyRuntimeContext.java:337)
... 11 more
2016-10-24 18:46:37 [INFO] Project Name=Amoeba-MySQL, PID=1577 , System shutdown ....
Java HotSpot(TM) 64-Bit Server VM warning: ignoring option PermSize=16m; support was removed in 8.0
Java HotSpot(TM) 64-Bit Server VM warning: ignoring option MaxPermSize=96m; support was removed in 8.0
2016-10-24 18:50:19 [INFO] Project Name=Amoeba-MySQL, PID=1602 , starting...
log4j:WARN log4j config load completed from file:/usr/local/amoeba/conf/log4j.xml
2016-10-24 18:50:21,668 INFO context.MysqlRuntimeContext - Amoeba for Mysql current versoin=5.1.45-mysql-amoeba-proxy-3.0.4-BETA
log4j:WARN ip access config load completed from file:/usr/local/amoeba/conf/access_list.conf
2016-10-24 18:50:22,852 INFO net.ServerableConnectionManager - Server listening on 0.0.0.0/0.0.0.0:8066.
查看端口
[root@bogon ~]# netstat -unlpt | grep java
tcp 0 0 :::8066 :::* LISTEN 1602/java
由此可知Amoeba启动正常
2.6 测试
远程登陆mysql客户端通过指定amoeba配置文件中指定的用户名、密码、和端口以及amoeba服务器ip地址链接mysql数据库
[root@lys2 ~]# mysql -h192.168.2.203 -uroot -p -P8066
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 1364055863
Server version: 5.1.45-mysql-amoeba-proxy-3.0.4-BETA Source distribution
Copyright (c) 2000, 2016, 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>
在testdb中创建表test并插入数据
mysql> use testdb;
Database changed
mysql> create table test_table(id int,password varchar(40) not null);
Query OK, 0 rows affected (0.19 sec)
mysql> show tables;
+------------------+
| Tables_in_testdb |
+------------------+
| test_table |
+------------------+
1 row in set (0.02 sec)
mysql> insert into test_table(id,password) values('1','test1');
Query OK, 1 row affected (0.04 sec)
mysql> select * from test_table;
+------+----------+
| id | password |
+------+----------+
| 1 | test1 |
+------+----------+
1 row in set (0.02 sec)
分别登陆masterdb和slavedb查看数据
masterdb：
mysql> use testdb;
Database changed
mysql> show tables;
+------------------+
| Tables_in_testdb |
+------------------+
| test_table |
+------------------+
1 row in set (0.00 sec)
mysql> select * from test_table;
+------+----------+
| id | password |
+------+----------+
| 1 | test1 |
+------+----------+
1 row in set (0.03 sec)
slavedb：
mysql> use testdb;
Database changed
mysql> show tables;
+------------------+
| Tables_in_testdb |
+------------------+
| test_table |
+------------------+
1 row in set (0.00 sec)
mysql> select * from test_table;
+------+----------+
| id | password |
+------+----------+
| 1 | test1 |
+------+----------+
1 row in set (0.00 sec)
停掉masterdb，然后在客户端分别执行插入和查询功能
masterdb：
[root@bogon ~]# service mysqld stop
Shutting down MySQL. SUCCESS!
客户端：
mysql> insert into test_table(id,password) values('2','test2');
ERROR 1044 (42000): Amoeba could not connect to MySQL server[192.168.2.204:3306],拒绝连接
mysql> select * from test_table;
+------+----------+
| id | password |
+------+----------+
| 1 | test1 |
+------+----------+
1 row in set (0.01 sec)
可以看到，关掉masterdb和写入报错，读正常
开启masterdb上的msyql 关闭slave上的mysql
masterdb：
[root@bogon ~]# service mysqld start
Starting MySQL.. SUCCESS!
slavedb：
[root@localhost ~]# service mysqld stop
Shutting down MySQL. SUCCESS!
客户端再次尝试
mysql> insert into test_table(id,password) values('2','test2');
Query OK, 1 row affected (0.19 sec)
mysql> select * from test_table;
ERROR 1044 (42000): poolName=myslave, no valid pools
可以看到插入成功，读取失败
开启slavedb上的mysql，查看数据是否自动同步
slavedb:
[root@localhost ~]# service mysqld start
Starting MySQL... SUCCESS!
客户端：
mysql> select * from test_table;
+------+----------+
| id | password |
+------+----------+
| 1 | test1 |
| 2 | test2 |
+------+----------+
2 rows in set (0.01 sec)
接着客户端：
mysql> insert into test_table(id,password) values('3','test3');
Query OK, 1 row affected (0.03 sec)
mysql> select * from test_table;
+------+----------+
| id | password |
+------+----------+
| 1 | test1 |
| 2 | test2 |
| 3 | test3 |
+------+----------+
3 rows in set (0.02 sec)
OK 一切正常，到此全部结束
注：关于mysql主从同步自行查看博主之前的主从同步笔记！
Amoeba主配置文件($AMOEBA_HOME/conf/amoeba.xml)，用来配置Amoeba服务的基本参数，如Amoeba主机地址、端口、认证方式、用于连接的用户名、密码、线程数、超时时间、其他配置文件的位置等。
数据库服务器配置文件($AMOEBA_HOME/conf/dbServers.xml)，用来存储和配置Amoeba所代理的数据库服务器的信息，如:主机IP、端口、用户名、密码等。
切分规则配置文件($AMOEBA_HOME/conf/rule.xml)，用来配置切分规则。
数据库函数配置文件($AMOEBA_HOME/conf/functionMap.xml)，用来配置数据库函数的处理方法，Amoeba将使用该配置文件中的方法解析数据库函数。
切分规则函数配置文件($AMOEBA_HOME/conf/ruleFunctionMap.xml)，用来配置切分规则中使用的用户自定义函数的处理方法。
访问规则配置文件($AMOEBA_HOME/conf/access_list.conf)，用来授权或禁止某些服务器IP访问Amoeba。
日志规格配置文件($AMOEBA_HOME/conf/log4j.xml)，用来配置Amoeba输出日志的级别和方式。