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MyCAT简易入门

MyCAT是mysql中间件，前身是阿里大名鼎鼎的Cobar，Cobar在开源了一段时间后，不了了之。于是MyCAT扛起了这面大旗，在大数据时代，其重要性愈发彰显。这篇文章主要是MyCAT的入门部署。

一、安装java

因Mycat是用java开发的，所以需要在实验环境下安装java，官方建议jdk1.7及以上版本

Java Oracle官方下载地址为：

http://www.oracle.com/technetwork/java/javase/archive-139210.html

解压jdk-7u79-linux-x64.tar.gz文件，并配置java的环境变量

# tar xvf jdk-7u79-linux-x64.tar.gz

# mv jdk1.7.0_79/ /usr/local/

编辑/etc/profile文件

# vim /etc/profile 添加如下内容

 export JAVA_HOME=/usr/local/jdk1.7.0_79 export PATH=$JAVA_HOME/bin:$PATH export CLASSPATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar

# source /etc/profile --使/etc/profile文件生效

# java -version

 java version "1.7.0_79" Java(TM) SE Runtime Environment (build 1.7.0_79-b15) Java HotSpot(TM) 64-Bit Server VM (build 24.79-b02, mixed mode)

二、安装MySQL

MySQL官方下载地址如下：

http://dev.mysql.com/downloads/mysql/

MyCAT简易入门

里面有各种版本，包括RPM，二进制，源码包。

为了方便起见，我这里选择是RPM包

# yum install -y mysql-community-server-5.6.26-2.el5.x86_64.rpm

启动MySQL

# /etc/init.d/mysqld start

 Starting mysqld (via systemctl):                           [  OK  ]

为root账户创建密码

# mysqladmin -u root password "123456"

建议为123456，后面MyCAT配置文件schema.xml中会用到

三、安装MyCAT

创建MyCAT用户并设置密码

# useradd mycat

# passwd mycat

解压MyCAT文件

# tar xvf Mycat-server-1.5-alpha-20151221110028-linux.tar.gz

# mv mycat/ /usr/local/

设置mycat目录的属主和属组

# chown -R mycat.mycat /usr/local/mycat/

四、测试MyCAT

首先在MySQL上创建三个数据库：db1，db2，db3。

 mysql> create database db1; Query OK, 1 row affected (0.00 sec)  mysql> create database db2; Query OK, 1 row affected (0.00 sec)  mysql> create database db3; Query OK, 1 row affected (0.00 sec)

启动mycat服务

# cd /usr/local/mycat/bin/

# ./mycat start

 Starting Mycat-server...

查看mycat服务是否启动

# ps -ef |grep mycat

 root       9640   7257  0 22:47 pts/3    00:00:00 grep --color=auto mycat

并没有启动

查看日志

# cd /usr/local/mycat/logs/

# cat wrapper.log

 STATUS | wrapper  | 2016/01/07 22:44:23 | --> Wrapper Started as Daemon STATUS | wrapper  | 2016/01/07 22:44:23 | Launching a JVM... ERROR  | wrapper  | 2016/01/07 22:44:25 | JVM exited while loading the application. INFO   | jvm 1    | 2016/01/07 22:44:25 | Error: Exception thrown by the agent : java.net.MalformedURLException: Local host name unknown: java.net.UnknownHostException: MySQL-Server1: MySQL-Server1: Name or service not known STATUS | wrapper  | 2016/01/07 22:44:29 | Launching a JVM... ERROR  | wrapper  | 2016/01/07 22:44:29 | JVM exited while loading the application. INFO   | jvm 2    | 2016/01/07 22:44:29 | Error: Exception thrown by the agent : java.net.MalformedURLException: Local host name unknown: java.net.UnknownHostException: MySQL-Server1: MySQL-Server1: Name or service not known STATUS | wrapper  | 2016/01/07 22:44:34 | Launching a JVM... ERROR  | wrapper  | 2016/01/07 22:44:34 | JVM exited while loading the application. INFO   | jvm 3    | 2016/01/07 22:44:34 | Error: Exception thrown by the agent : java.net.MalformedURLException: Local host name unknown: java.net.UnknownHostException: MySQL-Server1: MySQL-Server1: Name or service not known STATUS | wrapper  | 2016/01/07 22:44:38 | Launching a JVM... ERROR  | wrapper  | 2016/01/07 22:44:38 | JVM exited while loading the application. INFO   | jvm 4    | 2016/01/07 22:44:38 | Error: Exception thrown by the agent : java.net.MalformedURLException: Local host name unknown: java.net.UnknownHostException: MySQL-Server1: MySQL-Server1: Name or service not known STATUS | wrapper  | 2016/01/07 22:44:42 | Launching a JVM... ERROR  | wrapper  | 2016/01/07 22:44:43 | JVM exited while loading the application. INFO   | jvm 5    | 2016/01/07 22:44:43 | Error: Exception thrown by the agent : java.net.MalformedURLException: Local host name unknown: java.net.UnknownHostException: MySQL-Server1: MySQL-Server1: Name or service not known FATAL  | wrapper  | 2016/01/07 22:44:43 | There were 5 failed launches in a row, each lasting less than 300 seconds.  Giving up. FATAL  | wrapper  | 2016/01/07 22:44:43 |   There may be a configuration problem: please check the logs. STATUS | wrapper  | 2016/01/07 22:44:43 | <-- Wrapper Stopped

根据报错信息，怀疑主机名没有绑定

修改hosts文件，绑定主机名

# vim /etc/hosts

 127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4 ::1         localhost localhost.localdomain localhost6 localhost6.localdomain6 192.168.244.144 MySQL-Server1

重新启动mycat服务

# cd /usr/local/mycat/bin/

# ./mycat start

这次mycat正常启动

# ps -ef |grep mycat

 root      10725      1  0 22:54 ?        00:00:00 /usr/local/mycat/bin/./wrapper-linux-x86-64 /usr/local/mycat/conf/wrapper.conf wrapper.syslog.ident=mycat wrapper.pidfile=/usr/local/mycat/logs/mycat.pid wrapper.daemonize=TRUE wrapper.lockfile=/var/lock/subsys/mycat root      10881   7257  0 22:55 pts/3    00:00:00 grep --color=auto mycat

下面以Travelrecord为例，来进行插入，查询，路由分析等基本操作。

首先利用mycat连接mysql数据库

# mysql -utest -ptest -h127.0.0.1 -P8066 -DTESTDB

其中8066是mycat的监听端口，类似于mysql的3306端口，其中-u，-p，-h分别是用户名，密码和主机，-D是连接的逻辑库。

至于为什么是这些，这个跟配置文件有关。

MyCAT简易入门

红色部分表明连接的是mycat。

创建Travelrecord表

 create table travelrecord (id bigint not null primary key,user_id varchar(100),traveldate DATE, fee decimal,days int);

插入数据

 mysql> insert into travelrecord(id,user_id,traveldate,fee,days)  values(1,'Victor',20160101,100,10); Query OK, 1 row affected (0.00 sec)  mysql> insert into travelrecord(id,user_id,traveldate,fee,days)  values(5000001,'Job',20160102,100,10); Query OK, 1 row affected (0.00 sec)  mysql> insert into travelrecord(id,user_id,traveldate,fee,days)  values(10000001,'Slow',20160103,100,10); Query OK, 1 row affected (0.00 sec)

至于ID为什么取三个值，这个与conf目录下autopartition-long.txt的定义有关，这个文件主要定义auto-sharding-long的规则。

 # range start-end ,data node index # K=1000,M=10000. 0-500M=0 500M-1000M=1 1000M-1500M=2

我主要是测试在id取不同区间的值时，分片的效果。

下面来看看分片的效果

 mysql> select * from db1.travelrecord; +----+---------+------------+------+------+ | id | user_id | traveldate | fee  | days | +----+---------+------------+------+------+ |  1 | Victor  | 2016-01-01 |  100 |   10 | +----+---------+------------+------+------+ 1 row in set (0.00 sec)  mysql> select * from db2.travelrecord; +---------+---------+------------+------+------+ | id      | user_id | traveldate | fee  | days | +---------+---------+------------+------+------+ | 5000001 | Job     | 2016-01-02 |  100 |   10 | +---------+---------+------------+------+------+ 1 row in set (0.00 sec)  mysql> select * from db3.travelrecord; +----------+---------+------------+------+------+ | id       | user_id | traveldate | fee  | days | +----------+---------+------------+------+------+ | 10000001 | Slow    | 2016-01-03 |  100 |   10 | +----------+---------+------------+------+------+ 1 row in set (0.00 sec)

果然是分配到三个不同的节点上了。

如果想看MyCAT具体会将数据分配到哪个节点上，可通过路由分析。

语法其实蛮简单，就是SQL语句前加上explain语句。

下面根据explain命令查看create语句和insert语句具体会分配到哪些Datanode上。

 mysql> explain create table travelrecord (id bigint not null primary key,user_id varchar(100),traveldate DATE, fee decimal,days int); +-----------+-----------------------------------------------------------------------------------------------------------------------+ | DATA_NODE | SQL                                                                                                                   | +-----------+-----------------------------------------------------------------------------------------------------------------------+ | dn1       | create table travelrecord (id bigint not null primary key,user_id varchar(100),traveldate DATE, fee decimal,days int) | | dn2       | create table travelrecord (id bigint not null primary key,user_id varchar(100),traveldate DATE, fee decimal,days int) | | dn3       | create table travelrecord (id bigint not null primary key,user_id varchar(100),traveldate DATE, fee decimal,days int) | +-----------+-----------------------------------------------------------------------------------------------------------------------+ 3 rows in set (0.00 sec)  mysql>  explain insert into travelrecord(id,user_id,traveldate,fee,days)  values(1,'Victor',20160101,100,10); +-----------+----------------------------------------------------------------------------------------------+ | DATA_NODE | SQL                                                                                          | +-----------+----------------------------------------------------------------------------------------------+ | dn1       | insert into travelrecord(id,user_id,traveldate,fee,days)  values(1,'Victor',20160101,100,10) | +-----------+----------------------------------------------------------------------------------------------+ 1 row in set (0.01 sec)  mysql> explain insert into travelrecord(id,user_id,traveldate,fee,days)  values(5000001,'Job',20160102,100,10); +-----------+-------------------------------------------------------------------------------------------------+ | DATA_NODE | SQL                                                                                             | +-----------+-------------------------------------------------------------------------------------------------+ | dn2       | insert into travelrecord(id,user_id,traveldate,fee,days)  values(5000001,'Job',20160102,100,10) | +-----------+-------------------------------------------------------------------------------------------------+ 1 row in set (0.00 sec)  mysql> explain insert into travelrecord(id,user_id,traveldate,fee,days)  values(10000001,'Slow',20160103,100,10); +-----------+---------------------------------------------------------------------------------------------------+ | DATA_NODE | SQL                                                                                               | +-----------+---------------------------------------------------------------------------------------------------+ | dn3       | insert into travelrecord(id,user_id,traveldate,fee,days)  values(10000001,'Slow',20160103,100,10) | +-----------+---------------------------------------------------------------------------------------------------+ 1 row in set (0.00 sec)

总结：

关于MyCAT的配置其实是蛮简单的，最主要的是熟悉各配置文件的规则。以上用户名，密码，如何分库，都是在配置文件中定义的，后续，有时间再一一详表。

关于配置文件，conf目录下主要以下三个需要熟悉。

server.xml是Mycat服务器参数调整和用户授权的配置文件

schema.xml是逻辑库定义和表以及分片定义的配置文件

rule.xml是分片规则的配置文件

正文到此结束