MySQL数据同步【双主热备】

目录

 

• 应用环境
• 数据库同步方式
• 创建数据库表
• 配置数据库my.ini文件
  • my.ini文件简单释义
  • 配置双向同步
  • 配置项释义
• 设置主机并启动从服务器线程
  • show slave status
• 测试同步
• 解决自增长列的问题
• 模拟测试自增长列解决方案
• 故障排除
  • MySQL版本间复制兼容性问题
  • ERROR 1201 (HY000)

应用环境

 数据库服务器

 虚拟机

 OS:  Windows Server 2003

 1.数据库服务器242

　　IP:192.168.206.242

  2.数据库服务器243

　　IP:192.168.206.243

MySQL版本

版本号：5.5.2

查询语句：SELECT VERSION();

数据库同步方式

　　两台服务器互为主从，双向同步数据

　　

创建数据库表

 为试验双向同步，简单编写了一个创建数据库和一个用户表的语句。

 并分别在服务器242和243上的MySQL中执行语句。

CREATE DATABASE wilsondb;

USE wilsondb;

DROP TABLE IF EXISTS `userinfo`;

CREATE TABLE `userinfo` (

  `UserId` int(11) NOT NULL AUTO_INCREMENT,

  `UserName` varchar(64) DEFAULT NULL,

  PRIMARY KEY (`UserId`)

) ENGINE=InnoDB DEFAULT CHARSET=utf8;

配置数据库my.ini文件

在242和243服务器MySQL的安装目录下找到my.ini文件

1.my.ini文件各配置项简单释义

    # MySQL Server Instance Configuration File
    # ----------------------------------------------------------------------
    # Generated by the MySQL Server Instance Configuration Wizard
    #
    #
    # Installation Instructions
    # ----------------------------------------------------------------------
    #
    # On Linux you can copy this file to /etc/my.cnf to set global options,
    # mysql-data-dir/my.cnf to set server-specific options
    # (@localstatedir@ for this installation) or to
    # ~/.my.cnf to set user-specific options.
    #
    # On Windows you should keep this file in the installation directory 
    # of your server (e.g. C:\Program Files\MySQL\MySQL Server X.Y). To
    # make sure the server reads the config file use the startup option 
    # "--defaults-file". 
    #
    # To run run the server from the command line, execute this in a 
    # command line shell, e.g.
    # mysqld --defaults-file="C:\Program Files\MySQL\MySQL Server X.Y\my.ini"
    #
    # To install the server as a Windows service manually, execute this in a 
    # command line shell, e.g.
    # mysqld --install MySQLXY --defaults-file="C:\Program Files\MySQL\MySQL Server X.Y\my.ini"
    #
    # And then execute this in a command line shell to start the server, e.g.
    # net start MySQLXY
    #
    #
    # Guildlines for editing this file
    # ----------------------------------------------------------------------
    #
    # In this file, you can use all long options that the program supports.
    # If you want to know the options a program supports, start the program
    # with the "--help" option.
    #
    # More detailed information about the individual options can also be
    # found in the manual.
    #
    #
    # CLIENT SECTION
    # ----------------------------------------------------------------------
    #
    # The following options will be read by MySQL client applications.
    # Note that only client applications shipped by MySQL are guaranteed
    # to read this section. If you want your own MySQL client program to
    # honor these values, you need to specify it as an option during the
    # MySQL client library initialization.
    #
    # 客户端
    [client]
    
    # 端口号
    port=3306   
    
    [mysql]
    # 字符集
    default-character-set=utf8
    
    
    # SERVER SECTION
    # ----------------------------------------------------------------------
    #
    # The following options will be read by the MySQL Server. Make sure that
    # you have installed the server correctly (see above) so it reads this 
    # file.
    #
    [mysqld]
    
    # The TCP/IP Port the MySQL Server will listen on
    # MySQL端口号
    port=3306
    
    
    #Path to installation directory. All paths are usually resolved relative to this.
    # 安装路径
    basedir="C:/Program Files/MySQL/MySQL Server 5.5/"
    
    #Path to the database root
    # 数据库根路径
    datadir="C:/Documents and Settings/All Users/Application Data/MySQL/MySQL Server 5.5/Data/"
    
    # The default character set that will be used when a new schema or table is
    # created and no character set is defined
    # 字符集
    character-set-server=utf8
    
    # The default storage engine that will be used when create new tables when
    # 默认存储引擎
    default-storage-engine=INNODB
    
    # Set the SQL mode to strict
    # 设置严格SQL模型
    # 参数详细：http://www.cnblogs.com/ainiaa/archive/2010/12/31/1923002.html
    sql-mode="STRICT_TRANS_TABLES,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION"
    
    # The maximum amount of concurrent sessions the MySQL server will
    # allow. One of these connections will be reserved for a user with
    # SUPER privileges to allow the administrator to login even if the
    # connection limit has been reached.
    # 服务器端最大并发数，一个是留给超级管理员权限登录数据库
    max_connections=100
    
    # Query cache is used to cache SELECT results and later return them
    # without actual executing the same query once again. Having the query
    # cache enabled may result in significant speed improvements, if your
    # have a lot of identical queries and rarely changing tables. See the
    # "Qcache_lowmem_prunes" status variable to check if the current value
    # is high enough for your load.
    # Note: In case your tables change very often or if your queries are
    # textually different every time, the query cache may result in a
    # slowdown instead of a performance improvement.
    # 查询缓存的大小，Note：在查询常变，表结构常变的情况下，用缓存反而不好
    query_cache_size=0
    
    # The number of open tables for all threads. Increasing this value
    # increases the number of file descriptors that mysqld requires.
    # Therefore you have to make sure to set the amount of open files
    # allowed to at least 4096 in the variable "open-files-limit" in
    # section [mysqld_safe]
    # Table高速缓存的数量
    table_cache=256
    
    # Maximum size for internal (in-memory) temporary tables. If a table
    # grows larger than this value, it is automatically converted to disk
    # based table This limitation is for a single table. There can be many
    # of them.
    # 单张临时表的大小限制
    tmp_table_size=26M
    
    
    # How many threads we should keep in a cache for reuse. When a client
    # disconnects, the client's threads are put in the cache if there aren't
    # more than thread_cache_size threads from before.  This greatly reduces
    # the amount of thread creations needed if you have a lot of new
    # connections. (Normally this doesn't give a notable performance
    # improvement if you have a good thread implementation.)
    # 缓存多少线程给客户端使用
    thread_cache_size=8
    
    #*** MyISAM Specific options
    
    # The maximum size of the temporary file MySQL is allowed to use while
    # recreating the index (during REPAIR, ALTER TABLE or LOAD DATA INFILE.
    # If the file-size would be bigger than this, the index will be created
    # through the key cache (which is slower).
    # 重建索引时临时文件允许的最大值
    myisam_max_sort_file_size=100G
    
    # If the temporary file used for fast index creation would be bigger
    # than using the key cache by the amount specified here, then prefer the
    # key cache method.  This is mainly used to force long character keys in
    # large tables to use the slower key cache method to create the index.
    # 表发生变化重新排序需要的缓冲大小
    myisam_sort_buffer_size=52M
    
    # Size of the Key Buffer, used to cache index blocks for MyISAM tables.
    # Do not set it larger than 30% of your available memory, as some memory
    # is also required by the OS to cache rows. Even if you're not using
    # MyISAM tables, you should still set it to 8-64M as it will also be
    # used for internal temporary disk tables.
    # MyISAM表索引缓存大小，建议不要超过可用内存的30%
    key_buffer_size=8M
    
    # Size of the buffer used for doing full table scans of MyISAM tables.
    # Allocated per thread, if a full scan is needed.
    # MyISAM表全表扫描时的缓冲区大小（顺序读取）
    read_buffer_size=64K
    # 随机读取的缓冲区大小
    read_rnd_buffer_size=256K
    
    # This buffer is allocated when MySQL needs to rebuild the index in
    # REPAIR, OPTIMZE, ALTER table statements as well as in LOAD DATA INFILE
    # into an empty table. It is allocated per thread so be careful with
    # large settings.
    # 排序使用的缓冲区大小
    sort_buffer_size=256K
    
    
    #*** INNODB Specific options ***

    
    # Use this option if you have a MySQL server with InnoDB support enabled
    # but you do not plan to use it. This will save memory and disk space
    # and speed up some things.
    #skip-innodb
    
    # Additional memory pool that is used by InnoDB to store metadata
    # information.  If InnoDB requires more memory for this purpose it will
    # start to allocate it from the OS.  As this is fast enough on most
    # recent operating systems, you normally do not need to change this
    # value. SHOW INNODB STATUS will display the current amount used.
    # 设置InnoDB存储引擎存放数据字典信息和内部数据结构的内存大小
    innodb_additional_mem_pool_size=4M
    
    # If set to 1, InnoDB will flush (fsync) the transaction logs to the
    # disk at each commit, which offers full ACID behavior. If you are
    # willing to compromise this safety, and you are running small
    # transactions, you may set this to 0 or 2 to reduce disk I/O to the
    # logs. Value 0 means that the log is only written to the log file and
    # the log file flushed to disk approximately once per second. Value 2
    # means the log is written to the log file at each commit, but the log
    # file is only flushed to disk approximately once per second.
    # N（N是后面设置的值）次事务提交或事务外的指令就需要把日志写入硬盘
    innodb_flush_log_at_trx_commit=1
    
    # The size of the buffer InnoDB uses for buffering log data. As soon as
    # it is full, InnoDB will have to flush it to disk. As it is flushed
    # once per second anyway, it does not make sense to have it very large
    # (even with long transactions).
    # 设置InnoDB存储引擎的事务日志使用的缓冲区
    innodb_log_buffer_size=1520K
    
    # InnoDB, unlike MyISAM, uses a buffer pool to cache both indexes and
    # row data. The bigger you set this the less disk I/O is needed to
    # access data in tables. On a dedicated database server you may set this
    # parameter up to 80% of the machine physical memory size. Do not set it
    # too large, though, because competition of the physical memory may
    # cause paging in the operating system.  Note that on 32bit systems you
    # might be limited to 2-3.5G of user level memory per process, so do not
    # set it too high.
    # 设置InnoDB存放索引和表数据的最大缓冲区大小
    innodb_buffer_pool_size=147M
    
    # Size of each log file in a log group. You should set the combined size
    # of log files to about 25%-100% of your buffer pool size to avoid
    # unneeded buffer pool flush activity on log file overwrite. However,
    # note that a larger logfile size will increase the time needed for the
    # recovery process.
    # 一个InnoDB事条日志的大小
    innodb_log_file_size=74M
    
    # Number of threads allowed inside the InnoDB kernel. The optimal value
    # depends highly on the application, hardware as well as the OS
    # scheduler properties. A too high value may lead to thread thrashing.
    # InnoDB最大并发线程数
    innodb_thread_concurrency=8

    PS: 上面的折叠代码试验在chrome浏览器下需要手动刷一下页面才能展开

2.配置双向同步

242服务器上配置：

在[mysqld]这个Section中加入如下key/value对：

#---------------------------------------------

server-id=242

log-bin=mysql-bin

relay-log=relay-bin

relay-log-index=relay-bin-index

replicate-do-db=wilsondb

#---------------------------------------------

243服务器上配置：

在[mysqld]这个Section中加入如下key/value对：

 #---------------------------------------------

server-id=243

log-bin=mysql-bin

relay-log=relay-bin

relay-log-index=relay-bin-index

replicate-do-db=wilsondb

#---------------------------------------------

3.配置项释义【复制启动选项】

 ① server-id：标识，唯一，值范围在：1至2^23-1

 ② log-bin：配置是否在数据库有变动时写二进制日志

     查看日志是否开启：

     show variables like '%bin';

     

 ③ relay-log：这个不太会解释，Master二进制日志到Slave的IO进程会写到relay-log最后一行，Slave的sql进程时刻监测着relay-log是否有变化，有变化则解析执行. 

 ④ replicate-to-db:同步的数据库 

 ⑤ 其它复制启动选项： http://dev.mysql.com/doc/refman/5.1/zh/replication.html#replication-options

 在服务器242和243上配置好之后，分别重启MySQL服务，如果重启失败则说明配置有误!

 

设置主机并启动从服务器线程

 服务242上用MySQL命令行工具执行如下语句：

mysql> stop slave;

mysql> change master to master_host='192.168.206.243',master_user='root',master_password='abcd';

mysql> start slave;

mysql> show slave status\G;

#master_host的最大长度为60

#master_user的最大长度为16

#master_password最大长度为32

 

服务243上上用MySQL命令行工具执行如下语句：

mysql> stop slave;

mysql> change master tomaster_host='192.168.206.242',master_user='root',master_password='abcd';

mysql> start slave;

mysql> show slave status\G;

 Show Slave Status 部分释义

 ① Slave_IO_Status:线程已经连接上主服务器，正等待二进制日志事件到达。如果主服务器正空闲，会持续较长的时间。如果等待持续slave_read_timeout秒，则发生超时。此时，线程认为连接被中断并企图重新连接。

                              更多Slave_IO_Status: http://dev.mysql.com/doc/refman/5.1/zh/replication.html#slave-io-thread-states

 ② Master_Host: 主机IP

 ③ Master_Log_File和Master_LOG_POS选项执行CHANGE MASTER TO来告诉从服务器重新从该点读取二进制日志

 ④ Slave_IO_Running:是否要从Master复制二进制数据

 ⑤ Slave_SQL_Running:是否执行从Master复制过来的二进制数据

 ⑥ Slave_IO_Running和Slave_SQL_Running的值均为Yes时为同步开启;

 ⑦ Last_Errno和Last_Error是错误信息的提示（如果有错误）

 ⑧ Seconds_Behind_Master：Slave的数据落后Master的多少秒，同步完成为0

测试同步

  为了方便测试，装了一个Navicat for MySQL;

  对242和243数据库进行了双向的增、删、改操作;

  结果：最后都能正确的双向同步。

  

  

解决自增长列的问题

原因：当同步断开，两台服务器分别有新数据进入，那么主键ID是自增长列会出现冲突的情况，会导致同步无法继续。

在242和243服务器MySQL的安装目录下找到my.ini文件

分别在文件最后添入下面配置项：

服务器242：

#-------------------------------------

auto_increment_offset=1

auto_increment_increment=2

#-------------------------------------

服务器243：

#-------------------------------------

auto_increment_offset=2

auto_increment_increment=2

#-------------------------------------

查看修改后的属性值：

SHOW VARIABLES LIKE 'auto_inc%';

服务器242：

服务器243：

通过调整auto_increment_offset和auto_increment_increment让两台服务器自增长值不重复，这样多台服务器自增的问题就解决了;

（此项操作为了看自增更明显，我重新生成了表，然后再做了配置，其实本不需要重新生成表结构!）

模拟测试自增长列解决方案

测试过程模拟同步在断开后，两个数据库分别都有数据插入，然后再开启同步，是否会有自增ID的冲突。

1.先分别在服务器242和243上停止Slave线程

2.然后分别向服务器242和243所在数据库中分别插入数据

很明显，分别插入时，自增列也不会重复;

3.分别开启服务器242和243的Slave线程

4.查看同步后的数据

-------------------------------------------------------------

大功告成，同步成功，且没有发生冲突！

故障排除

 试验过程中遇到几个主要问题：

1.MySQL版本间复制兼容性

　 官方是推荐使用最近的版本，复制功能在不断改进中，同时推荐主从服务器使用相同的版本;

    为了避免出现一些兼容性的问题，这里两台数据库服务器上的MySQL安装了相同的版本;

　 不同MySQL版本之间的复制兼容性: http://dev.mysql.com/doc/refman/5.1/zh/replication.html#replication-compatibility

 2.ERROR 1201 (HY000): Could not initialize master info structure; more error messages can be found in the MySQL error log

　  在start slave;时出现error 1201(HY000)，出错后注意用show slave status\G 看错误提示（Last_IO_Error和Last_SQL_Error）。后台根据提示定位是在没关掉同步的情况下进行了一些冲突的SQL操作，

     解决步骤： ① 停止SQL服务

                    ② 删除master.info和relay-log.info文件

                    ③ change master to  master_host='XXXXXX',

                        master_user='XXXX',master_password='XXXX';

                    ④ 重启SQL服务器，再start slave;

 

  过程中远不止遇到这几个错误，没记录下细节，都是看相关提示修正的，都是些操作问题或者是细心问题;