MyCAT简易入门

http://www.cnblogs.com/tengpan-cn/p/5996020.html

https://blog.csdn.net/l1028386804/article/details/75269196

https://www.cnblogs.com/ivictor/p/5131480.html

https://aws.amazon.com/cn/blogs/china/mycat-rds-mysql/

https://blog.csdn.net/l1028386804/article/details/75269196

https://www.cnblogs.com/ivictor/p/5131480.html

从开始接触mycat，到现在为止也有三个多月的时间了，目前在测试环境中已经初步应用！大概可以总结一下了

mycat是一个数据库中间件，也可以理解为是数据库代理。在架构体系中是位于数据库和应用层之间的一个组件，并且对于应用层是透明的，即数据库感受不到mycat的存在，认为是直接连接的mysql数据库（实际上是连接的mycat,mycat实现了mysql的原生协议）

mycat的三大功能：分表、读写分离、主从切换。

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

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/

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。

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)