mysql读写分离,中间件用mycat
首先，数据库的读写分离，能让应用对数据库的访问压力下降，较之一台数据库服务器来读写的时候。
2台数据库服务器，1台用来执行写操作，1台用来执行读操作，这样能够分散应用对数据的压力，而且能加强数据库的数据安全性。
所以，面对比较大型的数据读取应用，对其数据库做读写分离，对性能提升是很有好处的。
为什么读写分离可以提高性能？
- 物理服务器增加，负荷增加
- 主从只负责各自的写和读，极大程度的缓解X锁和S锁争用
- 从库可配置myisam引擎，提升查询性能以及节约系统开销
- 至于你提到的“master所执行的（写）的所有语句，都会在slave被执行一遍”这个只说对一半，从库同步主库的数据和主库直接写还是有区别的，通过主库发送来的binlog恢复数据，但是，最重要区别在于主库向从库发送binlog是异步的，从库恢复数据也是异步的。
- 读写分离适用与读远大于写的场景，如果只有一台服务器，当select很多时，update和delete会被这些select访问中的数据堵塞，等待select结束，并发性能不高。 对于写和读比例相近的应用，应该部署双主相互复制。
主要步骤
- 1.mysql主从数据库设置，master用来做写操作，slave用来做读操作。
主从数据库设置，是指slave会通过mysql的主从复制功能，自动去实时去同步master上的数据变更。（单向的slave copy master）
- 2.mycat设置简单的读写分离，并启动，对应用程序端提供mysql porxy代理服务。
mycat是一款国人开发的数据库代理中间件，功能强大，可以支持多种数据库，支持分库分表。
实际操作
- 1.搭建mysql的master-slave环境
有2台MySQL数据库主机，IP分别为192.168.1.113 和 192.168.1.109。
把109做master，用来写入数据，执行insert,update,delete等操作。
把113做slave，用来读取数据，执行select查询操作。
- 1.1.配置master
在mysql的配置文件中my.ini的[mysqld]节点下加上如下配置：
log-bin=mysql-bin #slave会基于此log-bin来做replication
server-id = 1 #master的标示
binlog-do-db = jpress #用于master-slave的具体数据库
然后给复制集配置复制的用户，执行如下命令。
然后添加专门用于replication的用户：
mysql> GRANT REPLICATION SLAVE ON *.* TO [email protected] IDENTIFIED BY '123456';
重启mysql服务，然后查看show master status;
mysql> show master status;
+------------------+----------+--------------+------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+------------------+----------+--------------+------------------+
| mysql-bin.000008 | 107 | jpress | |
+------------------+----------+--------------+------------------+
1 row in set (0.00 sec)
- 1.2.配置slave
补上遗漏的部分：2016-12-22
slave上的my.ini的[mysqld]节点下加上如下配置：
server-id = 2 #slave的标示,推荐使用IP的第4部分
#其他配置可以百度mysql主从复制详细配置
#relay-log-index=slave-relay-bin.index
#relay-log=slave-relay-bin
如果有配置主从，要先关闭stop slave;，然后再执行如下命令，来配置主从设置：
CHANGE MASTER TO
MASTER_HOST='192.168.1.109',
MASTER_USER='xiaogang',
MASTER_PASSWORD='123456',
MASTER_LOG_FILE='mysql-bin.000008',
MASTER_LOG_POS= 107;
其中用户就是master数据库服务器上分配的用户，file和pos是master上的show master status;中的file和position。
执行完之后，启动主从关联，slave start;，然后使用show slave status;\G来查看从服务器状态。
mysql> show slave status\G;
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 192.168.1.109
Master_User: xiaogang
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000008
Read_Master_Log_Pos: 107
Relay_Log_File: PC-20150410VNLS-relay-bin.000008
Relay_Log_Pos: 253
Relay_Master_Log_File: mysql-bin.000008
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
Replicate_Do_DB:
Replicate_Ignore_DB:
Replicate_Do_Table:
Replicate_Ignore_Table:
Replicate_Wild_Do_Table:
Replicate_Wild_Ignore_Table:
Last_Errno: 0
Last_Error:
Skip_Counter: 0
Exec_Master_Log_Pos: 107
Relay_Log_Space: 565
Until_Condition: None
Until_Log_File:
Until_Log_Pos: 0
Master_SSL_Allowed: No
Master_SSL_CA_File:
Master_SSL_CA_Path:
Master_SSL_Cert:
Master_SSL_Cipher:
Master_SSL_Key:
Seconds_Behind_Master: 0
Master_SSL_Verify_Server_Cert: No
Last_IO_Errno: 0
Last_IO_Error:
Last_SQL_Errno: 0
Last_SQL_Error:
Replicate_Ignore_Server_Ids:
Master_Server_Id: 1
1 row in set (0.01 sec)
其中
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
都是yes则说明主从配置已经生效。{意味着在master数据库jpress上的操作都会被同步到slave上}。
如是，MySQL的主从复制就已经搭建完毕，注意是从 copy 主，是单向复制的，也就是说write得指定是master。
- 2.基于mycat来搭建读写分离
- 2.1.先下载mycat
具体了解，请参考mycat官网：http://www.mycat.org.cn/
到https://github.com/MyCATApache/Mycat-download/tree/master/1.6-RELEASE 下载最新版本1.6，根据自己的OS来。
下载后的目录如下（mac平台下）：
- 2.2.简单配置mycat的读写分离
server.xml
meigang2016
testdb
schema.xml
show slave status
-
2.3.启动mycat
unix/linux 启动命令
meigangdeMacBook-Pro:bin meigang$ ./mycat start
Starting Mycat-server…
查看启动日志，表示启动成功。
INFO | jvm 1 | 2016/10/18 15:46:16 | MyCAT Server startup successfully. see logs in logs/mycat.log
INFO | jvm 1 | 2016/10/18 15:46:17 | 2016-10-18 15:46:16,991 [INFO ][$_NIOREACTOR-1-RW] connectionAcquired MySQLConnection [id=13, lastTime=1476776776969, user=xiaogang, schema=jpress, old shema=jpress, borrowed=false, fromSlaveDB=true, threadId=14, charset=utf8, txIsolation=3, autocommit=true, attachment=null, respHandler=null, host=192.168.1.113, port=3306, statusSync=null, writeQueue=0, modifiedSQLExecuted=false] (io.mycat.backend.mysql.nio.handler.NewConnectionRespHandler:NewConnectionRespHandler.java:45)
使用mysql命令行工具，登录8066端口，验证mycat启动数据库代理成功。
meigangdeMacBook-Pro:bin meigang$ mysql -P8066 -uroot -p
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 27
Server version: 5.5.50-log MySQL Community Server (GPL)
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>
- 3.使用jpress开源Java博客系统来链接8066的testdb数据库服务，做验证。
将jpress压缩成war后放到tomcat的webapps中，运行后得到解压后的项目，把war删掉。
进去找到/web-inf/classes/db.properties，修改如下：
#Auto create by JPress
#Mon Oct 17 18:54:30 CST 2016
db_name=testdb
db_host_port=8066
db_tablePrefix=jpress_
db_host=localhost
db_password=meigang2016
db_user=root
启动tomcat，查看master和slave上的执行sql的日志。可以发现master上执行的多是update,delete,insert的，而slave上执行的
多是select（有ddl的，应该是slave去同步master上执行的）
MySQL启用日志：
set global general_log = on;
show variables like ‘general_log_file’;去查看该文件，就可以查看该数据库上执行的sql.
如下是master 109上执行的日志。都是ddl的。
Time Id Command Argument
161018 16:16:35 28 Query show variables like 'general_log_file'
161018 16:16:36 22 Query show slave status
161018 16:16:41 28 Query set global general_log = on
161018 16:16:45 28 Query show variables like 'general_log_file'
161018 16:16:46 20 Query show slave status
161018 16:16:56 26 Query show slave status
161018 16:17:06 23 Query show slave status
161018 16:17:11 21 Query SET names utf8;update `jpress_content` set `view_count` = 1 where `id` = '4'
161018 16:17:16 25 Query show slave status
161018 16:17:25 17 Query SET names utf8;update `jpress_content` set `view_count` = 5 where `id` = '3'
161018 16:17:26 19 Query show slave status
161018 16:17:36 18 Query show slave status
161018 16:17:46 24 Query show slave status
161018 16:17:56 22 Query show slave status
161018 16:18:06 20 Query show slave status
161018 16:18:09 26 Query SET autocommit=0;insert into `jpress_content`(`module`, `text`, `status`, `meta_keywords`, `comment_status`, `remarks`, `lng`, `modified`, `id`, `title`, `thumbnail`, `flag`, `meta_description`, `created`, `user_id`, `slug`, `lat`) values('page', '测试
', 'normal', null, null, null, null, '2016-10-18 16:18:09', null, '测试', null, null, null, '2016-10-18 16:18:09', '1', '测试', null)
161018 16:18:10 26 Query SELECT COUNT(*) FROM `jpress_comment` WHERE content_id = '5' and status='normal'
26 Query DELETE FROM `jpress_mapping` WHERE content_id = '5'
26 Query commit
26 Query rollback
23 Query SET names utf8;update `jpress_content` set `text` = '测试
' where `id` = 5
21 Query update `jpress_user` set `content_count` = 3 where `id` = '1'
161018 16:18:16 25 Query show slave status
如下是slave 113上执行的日志。多是select的，还有用来同步数据的sql.
161018 16:22:54 19 Query select 1
12 Query select * from `jpress_user` where `id` = '1'
13 Query select * from `jpress_content` c where module = 'menu' ORDER BY c.order_number ASC
16 Query select count(*) from `jpress_content` c left join `jpress_mapping` m on c.id = m.`content_id` left join `jpress_taxonomy` t on m.`taxonomy_id` = t.id left join `jpress_user` u on c.user_id = u.id WHERE ( c.module = 'article' ) AND c.status = 'normal' group by c.id
17 Query select c.*,GROUP_CONCAT(t.id ,':',t.slug,':',t.title,':',t.type SEPARATOR ',') as taxonomys,u.username,u.nickname,u.avatar from `jpress_content` c left join `jpress_mapping` m on c.id = m.`content_id` left join `jpress_taxonomy` t on m.`taxonomy_id` = t.id left join `jpress_user` u on c.user_id = u.id WHERE ( c.module = 'article' ) AND c.status = 'normal' group by c.id ORDER BY c.created DESC limit 0, 10
18 Query select c.*,GROUP_CONCAT(t.id ,':',t.slug,':',t.title,':',t.type SEPARATOR ',') as taxonomys ,u.username,u.nickname,u.avatar from `jpress_content` c left join `jpress_mapping` m on c.id = m.`content_id` left join `jpress_taxonomy` t on m.`taxonomy_id` = t.id left join `jpress_user` u on c.user_id = u.id where c.status = 'normal' AND ( c.module = 'article' ) AND ( c.flag like '%hot%' ) GROUP BY c.id ORDER BY c.created DESC LIMIT 0, 3
14 Query select c.*,GROUP_CONCAT(t.id ,':',t.slug,':',t.title,':',t.type SEPARATOR ',') as taxonomys ,u.username,u.nickname,u.avatar from `jpress_content` c left join `jpress_mapping` m on c.id = m.`content_id` left join `jpress_taxonomy` t on m.`taxonomy_id` = t.id left join `jpress_user` u on c.user_id = u.id where c.status = 'normal' AND ( c.module = 'article' ) AND c.thumbnail is not null GROUP BY c.id ORDER BY c.comment_count DESC LIMIT 0, 3
15 Query select c.*,GROUP_CONCAT(t.id ,':',t.slug,':',t.title,':',t.type SEPARATOR ',') as taxonomys ,u.username,u.nickname,u.avatar from `jpress_content` c left join `jpress_mapping` m on c.id = m.`content_id` left join `jpress_taxonomy` t on m.`taxonomy_id` = t.id left join `jpress_user` u on c.user_id = u.id where c.status = 'normal' AND ( c.module = 'article' ) AND c.thumbnail is not null GROUP BY c.id ORDER BY c.view_count DESC LIMIT 0, 10
19 Query SELECT * FROM `jpress_taxonomy` t WHERE t.content_module = 'article' AND t.`type` = 'tag' ORDER BY t.created DESC limit 10
161018 16:22:56 12 Query SELECT * FROM `jpress_taxonomy` t WHERE t.content_module = 'article' AND ( t.`slug` = 'mysql' )
13 Query SELECT * FROM `jpress_content` WHERE module = 'menu' and object_id = '1' order by id desc
16 Query select count(*) from `jpress_content` c left join `jpress_mapping` m on c.id = m.`content_id` left join `jpress_taxonomy` t on m.`taxonomy_id` = t.id left join `jpress_user` u on c.user_id = u.id WHERE c.status = 'normal' AND c.module = 'article' AND exists(select 1 from `jpress_mapping` m where m.`taxonomy_id` in (1) and m.`content_id`=c.id) group by c.id
17 Query select c.*,GROUP_CONCAT(t.id ,':',t.slug,':',t.title,':',t.type SEPARATOR ',') as taxonomys,u.username,u.nickname,u.avatar from `jpress_content` c left join `jpress_mapping` m on c.id = m.`content_id` left join `jpress_taxonomy` t on m.`taxonomy_id` = t.id left join `jpress_user` u on c.user_id = u.id WHERE c.status = 'normal' AND c.module = 'article' AND exists(select 1 from `jpress_mapping` m where m.`taxonomy_id` in (1) and m.`content_id`=c.id) group by c.id ORDER BY c.created DESC limit 0, 10
18 Query select c.*,GROUP_CONCAT(t.id ,':',t.slug,':',t.title,':',t.type SEPARATOR ',') as taxonomys ,u.username,u.nickname,u.avatar from `jpress_content` c left join `jpress_mapping` m on c.id = m.`content_id` left join `jpress_taxonomy` t on m.`taxonomy_id` = t.id left join `jpress_user` u on c.user_id = u.id where c.status = 'normal' AND ( c.module = 'article' ) AND c.thumbnail is not null GROUP BY c.id ORDER BY c.comment_count DESC LIMIT 0, 3
14 Query select c.*,GROUP_CONCAT(t.id ,':',t.slug,':',t.title,':',t.type SEPARATOR ',') as taxonomys ,u.username,u.nickname,u.avatar from `jpress_content` c left join `jpress_mapping` m on c.id = m.`content_id` left join `jpress_taxonomy` t on m.`taxonomy_id` = t.id left join `jpress_user` u on c.user_id = u.id where c.status = 'normal' AND ( c.module = 'article' ) AND c.thumbnail is not null GROUP BY c.id ORDER BY c.view_count DESC LIMIT 0, 10
161018 16:22:57 15 Query show slave status
19 Query select c.*,GROUP_CONCAT(t.id ,':',t.slug,':',t.title,':',t.type SEPARATOR ',') as taxonomys ,u.username,u.nickname,u.avatar from `jpress_content` c left join `jpress_mapping` m on c.id = m.`content_id` left join `jpress_taxonomy` t on m.`taxonomy_id` = t.id left join `jpress_user` u on c.user_id = u.id WHERE c.id = '3' GROUP BY c.id
21 Connect xiaogang@MACBOOKPRO-E61D on jpress
2 Query BEGIN
12 Query select t.* from `jpress_taxonomy` t left join `jpress_mapping` m on t.id = m.taxonomy_id where m.content_id = '3'
2 Query update `jpress_content` set `view_count` = 6 where `id` = '3'
2 Query COMMIT /* implicit, from Xid_log_event */
13 Query select count(*) from `jpress_comment` c left join `jpress_content` on c.content_id = `jpress_content`.id left join `jpress_user` u on c.user_id = u.id left join `jpress_comment` quote_comment on c.parent_id = quote_comment.id left join `jpress_user` quote_user on quote_comment.user_id = quote_user.id WHERE c.`status` = 'normal' AND `jpress_content`.id = '3'
16 Query select c.*,`jpress_content`.title content_title,u.username,u.nickname,u.avatar, quote_comment.text qc_content,quote_comment.author qc_author,quote_user.username qc_username,quote_user.nickname qc_nickname,quote_user.avatar qc_avatar from `jpress_comment` c left join `jpress_content` on c.content_id = `jpress_content`.id left join `jpress_user` u on c.user_id = u.id left join `jpress_comment` quote_comment on c.parent_id = quote_comment.id left join `jpress_user` quote_user on quote_comment.user_id = quote_user.id WHERE c.`status` = 'normal' AND `jpress_content`.id = '3' order by c.created desc limit 0, 10
17 Query select c.*,GROUP_CONCAT(t.id ,':',t.slug,':',t.title,':',t.type SEPARATOR ',') as taxonomys ,u.username,u.nickname,u.avatar from `jpress_content` c left join `jpress_mapping` m on c.id = m.`content_id` left join `jpress_taxonomy` t on m.`taxonomy_id` = t.id left join `jpress_user` u on c.user_id = u.id where c.status = 'normal' AND ( c.module = 'article' ) AND c.thumbnail is not null GROUP BY c.id ORDER BY c.comment_count DESC LIMIT 0, 3
18 Query select c.*,GROUP_CONCAT(t.id ,':',t.slug,':',t.title,':',t.type SEPARATOR ',') as taxonomys ,u.username,u.nickname,u.avatar from `jpress_content` c left join `jpress_mapping` m on c.id = m.`content_id` left join `jpress_taxonomy` t on m.`taxonomy_id` = t.id left join `jpress_user` u on c.user_id = u.id where c.status = 'normal' AND ( c.module = 'article' ) AND c.thumbnail is not null GROUP BY c.id ORDER BY c.view_count DESC LIMIT 0, 10
161018 16:23:07 14 Query show slave status
161018 16:23:17 15 Query show slave status
161018 16:23:27 19 Query show slave status
161018 16:23:37 21 Query show slave status
- 4.查看博客效果
