MySQL数据同步【双主热备】_MySQL

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• 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)

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();

　　两台服务器互为主从，双向同步数据

　　

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;

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

my.ini详情及简单释义

    # 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    # ( 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 inpidual 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!

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

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。

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!）

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！

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;

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