MyCAT简易入门

时间 2016-01-08 12:45:00 博客园精华区

原文  http://www.cnblogs.com/ivictor/p/5111495.html

主题 MySQL

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=$JAVA_HOME/bin:$PATHexport 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 RuntimeEnvironment(build 1.7.0_79-b15)JavaHotSpot(TM)64-BitServer 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/

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

Startingmysqld(viasystemctl):[  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

StartingMycat-server...

查看mycat服务是否启动

# ps -ef |grep mycat

root       96407257022:47 pts/300:00:00 grep --color=auto mycat

并没有启动

查看日志

# cd /usr/local/mycat/logs/

# cat wrapper.log

STATUS | wrapper  |2016/01/0722:44:23|-->WrapperStartedasDaemon
STATUS | wrapper  |2016/01/0722:44:23|Launching a JVM...
ERROR  | wrapper  |2016/01/0722:44:25| JVM exited while loading the application.
INFO   | jvm 1|2016/01/0722:44:25|Error:Exception thrown by the agent : java.net.MalformedURLException:Local host name unknown: java.net.UnknownHostException:MySQL-Server1:MySQL-Server1:Nameor service not known
STATUS | wrapper  |2016/01/0722:44:29|Launching a JVM...
ERROR  | wrapper  |2016/01/0722:44:29| JVM exited while loading the application.
INFO   | jvm 2|2016/01/0722:44:29|Error:Exception thrown by the agent : java.net.MalformedURLException:Local host name unknown: java.net.UnknownHostException:MySQL-Server1:MySQL-Server1:Nameor service not known
STATUS | wrapper  |2016/01/0722:44:34|Launching a JVM...
ERROR  | wrapper  |2016/01/0722:44:34| JVM exited while loading the application.
INFO   | jvm 3|2016/01/0722:44:34|Error:Exception thrown by the agent : java.net.MalformedURLException:Local host name unknown: java.net.UnknownHostException:MySQL-Server1:MySQL-Server1:Nameor service not known
STATUS | wrapper  |2016/01/0722:44:38|Launching a JVM...
ERROR  | wrapper  |2016/01/0722:44:38| JVM exited while loading the application.
INFO   | jvm 4|2016/01/0722:44:38|Error:Exception thrown by the agent : java.net.MalformedURLException:Local host name unknown: java.net.UnknownHostException:MySQL-Server1:MySQL-Server1:Nameor service not known
STATUS | wrapper  |2016/01/0722:44:42|Launching a JVM...
ERROR  | wrapper  |2016/01/0722:44:43| JVM exited while loading the application.
INFO   | jvm 5|2016/01/0722:44:43|Error:Exception thrown by the agent : java.net.MalformedURLException:Local host name unknown: java.net.UnknownHostException:MySQL-Server1:MySQL-Server1:Nameor service not known
FATAL  | wrapper  |2016/01/0722:44:43|There were 5 failed launches in a row,each lasting less than 300 seconds.Giving up.
FATAL  | wrapper  |2016/01/0722:44:43|There may be a configuration problem: please check the logs.
STATUS | wrapper  |2016/01/0722:44:43|<--WrapperStopped

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

127.0.0.1localhostlocalhost.localdomainlocalhost4localhost4.localdomain4::1localhostlocalhost.localdomainlocalhost6localhost6.localdomain6192.168.244.144MySQL-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      107251022:54?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      108817257022:55 pts/300:00:00 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。

红色部分表明连接的是mycat。

创建Travelrecord表

createtable travelrecord (id bigint notnullprimarykey,user_id varchar(100),traveldate DATE, fee decimal,days int);

插入数据

mysql>insertinto travelrecord(id,user_id,traveldate,fee,days)values(1,'Victor',20160101,100,10);Query OK,1 row affected (0.00 sec)

mysql>insertinto travelrecord(id,user_id,traveldate,fee,days)values(5000001,'Job',20160102,100,10);Query OK,1 row affected (0.00 sec)

mysql>insertinto 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=0500M-1000M=11000M-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 inset(0.00 sec)

mysql>select*from db2.travelrecord;+---------+---------+------------+------+------+| id      | user_id | traveldate | fee  | days |+---------+---------+------------+------+------+|5000001|Job|2016-01-02|100|10|+---------+---------+------------+------+------+1 row inset(0.00 sec)

mysql>select*from db3.travelrecord;+----------+---------+------------+------+------+| id       | user_id | traveldate | fee  | days |+----------+---------+------------+------+------+|10000001|Slow|2016-01-03|100|10|+----------+---------+------------+------+------+1 row inset(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 createtable travelrecord (id bigint notnullprimarykey,user_id varchar(100),traveldate DATE, fee decimal,days int);+-----------+-----------------------------------------------------------------------------------------------------------------------+| DATA_NODE | SQL                                                                                                                   |+-----------+-----------------------------------------------------------------------------------------------------------------------+| dn1       |createtable travelrecord (id bigint notnullprimarykey,user_id varchar(100),traveldate DATE, fee decimal,days int)|| dn2       |createtable travelrecord (id bigint notnullprimarykey,user_id varchar(100),traveldate DATE, fee decimal,days int)|| dn3       |createtable travelrecord (id bigint notnullprimarykey,user_id varchar(100),traveldate DATE, fee decimal,days int)|+-----------+-----------------------------------------------------------------------------------------------------------------------+3rowsinset(0.00 sec)

mysql>  explain insertinto travelrecord(id,user_id,traveldate,fee,days)values(1,'Victor',20160101,100,10);+-----------+----------------------------------------------------------------------------------------------+| DATA_NODE | SQL                                                                                          |+-----------+----------------------------------------------------------------------------------------------+| dn1       |insertinto travelrecord(id,user_id,traveldate,fee,days)values(1,'Victor',20160101,100,10)|+-----------+----------------------------------------------------------------------------------------------+1 row inset(0.01 sec)

mysql> explain insertinto travelrecord(id,user_id,traveldate,fee,days)values(5000001,'Job',20160102,100,10);+-----------+-------------------------------------------------------------------------------------------------+| DATA_NODE | SQL                                                                                             |+-----------+-------------------------------------------------------------------------------------------------+| dn2       |insertinto travelrecord(id,user_id,traveldate,fee,days)values(5000001,'Job',20160102,100,10)|+-----------+-------------------------------------------------------------------------------------------------+1 row inset(0.00 sec)

mysql> explain insertinto travelrecord(id,user_id,traveldate,fee,days)values(10000001,'Slow',20160103,100,10);+-----------+---------------------------------------------------------------------------------------------------+| DATA_NODE | SQL                                                                                               |+-----------+---------------------------------------------------------------------------------------------------+| dn3       |insertinto travelrecord(id,user_id,traveldate,fee,days)values(10000001,'Slow',20160103,100,10)|+-----------+---------------------------------------------------------------------------------------------------+1 row inset(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