MyCAT简单入门

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、linux环境下安装java

step1：下载jdk

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

第三方下载地址(速度快)

step2：解压jdk压缩包

解压jdk-7u79-linux-x64.tar.gz文件

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

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

step3：配置java环境变量，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文件立即生效
# java -version				检测jdk是否安装成功

二、linux下安装MySQL

step1：下载mysql

MySQL官方下载

推荐使用docker安装

里面有各种版本，包括RPM，二进制，源码包。为了方便，下载RPM包

step2：安装mysql

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

step3：启动MySQL

# /etc/init.d/mysqld start
# systemctl start mysql.service 启动方式二

step4：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

step1：linux服务器创建一个新的MyCAT用户并设置密码

# useradd mycat
# passwd mycat

step2：解压MyCAT文件

# tar xvf Mycat-server-1.5-alpha-20151221110028-linux.tar.gz
# mv mycat/ /usr/local/

step3:设置mycat目录的属主和属组

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

四、测试MyCAT

step1:在MySQL上创建三个数据库：db1，db2，db3

mysql> create database db1;
mysql> create database db2;
mysql> create database db3;

step2:启动mycat服务

# cd /usr/local/mycat/bin/
# ./mycat start
Starting Mycat-server...

step:3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

step4: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

step5: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

step6: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表为例，来进行插入，查询，路由分析等基本操作。

step7：使用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。

红色部分表明连接的是mycat

step8：创建Travelrecord表

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

插入三条数据

mysql> insert into travelrecord(id,user_id,traveldate,fee,days)  values(1,'Victor',20160101,100,10);

mysql> insert into travelrecord(id,user_id,traveldate,fee,days)  values(5000001,'Job',20160102,100,10);

mysql> insert into travelrecord(id,user_id,traveldate,fee,days)  values(10000001,'Slow',20160103,100,10);

至于ID为什么取三个值，这个与MyCat的conf目录下autopartition-long.txt（自动分区）的定义有关，这个文件主要定义auto-sharding-long（自动分片）规则。

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

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。

step9：如果想查看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