什么是Mysql的多实例？
简单的说，Mysql多实例就是一台服务器上同时开启多个不同的服务端口（如3306、3307）同时运行多个Mysql服务进程，这些服务进程通过不同socket监听不同的服务端口来提供服务。
Msyql的多实例特点：
这些Mysql共用一套Mysql的安装程序，使用不用的配置文件（my.cnf）启动程序和数据文件。在提供服务时，多实例Mysql在逻辑上看起来是各自独立的，它们根据配置文件的对应设定值，获得服务器响应数量的硬件资源。
补充：
其实很多网络服务器都是可以配置多实例的，例如Nginx Apache Redis Memcache 都可以配置多实例。
mysql多实例的作用：
1）有效的利用服务器资源 当单个服务器资源有剩余的时候，可以充分利用剩余的资源提供更多的服务，且可以实现资源的逻辑隔离。 2）节约服务器资源 当公司资金紧张，但是数据库又需要各自尽量独立提供服务，而且，需要主从复制等多实例就再好不过了。 但是 mysql多实例也有弊端，当某个数据库实例并发很高或者SQL满查询时，会存在资源相互抢占的问题。
Mysql多实例的生产应用场景
1.资金紧张型公司的选择
比如： 3台服务器部署9-15个实例，交叉做主从复制，数据备份及读写分离，这样就可以达到9-15台服务器每个只装一个数据库才有的效果。所谓的独立是相对的。
2.并发访问不是很大的业务
当公司业务量不太大时候，服务器的资源基本都是浪费的，这时就很适合多实例的应用，如果对SQL语句的优化做的比较好，Mysql多实例会是一个很值得使用的技术，即可并发很大，合理分配系统资源以及搭配好服务，也不会有太大问题。
3.门户网站应用Mysql多实例场景
例如：百度公司，某部门中IBM服务器为48核CPU，内存96GB 。这样配置服务器可以跑3-4个实例；sina网也是用的多实例，内存48G左右。
补充：sina网的数据库单机1-4数据库实例居多，其中多数1-2个的最多，因为大业务占用的机器多。服务器是DELL R510居多，CPU E5210 48G内存 硬盘 12*300G SAS 做RAID10 ；另外，sina网站安装数据库时，一般采用编译安装方式安装，并在做好优化之后定制成rpm包，以便统一使用.
Mysql多实例配置方案
1.单一配置文件，单一启动程序多实例部署方案
Mysql官方文档提到的单一配置文件，单一启动程序多实例部署实例，不推荐此方案，这里作为知识点提及。官方my.cnf配置文件示例配置如下：
[mysqld_multil] mysqld = /usr/bin/mysqld_safe mysqladmin = /usr/bin/mysqladmin user = mysql [mysqld1] socket = /var/lib/mysql/mysql.sock port = 3306 pid-file = /var/lib/mysql/mysql.pid datadir = /var/lib/mysql/ user = mysql [mysqld2] socket =/mnt/data/db1/mysql.sock port = 3302 pid-file = /mnt/data/db1/mysql.pid datadir = /mnt/data/db1/ user = mysql skip-name-resolve server-id=10 dafault-storage-engine=innodb innodb_buffer_pool_size=512M innodb_additional_mem_pool=10M default_character_set=utf8 character_set_server=utf8 #read-only relay-log-space-limit=3G expire_logs_day=20
启动命令如下：mysqld_multi --config-file=/data/mysql/my_multi.cnf start 1,2
对于该方案，缺点是耦合度太高，一个配置文件，不好管理，工作开发和运维的统一原则，降低耦合度。
2.多配置文件多启动程序部署方案
多配置文件，多启动程序部署方案，是推荐的方案。下面来看配置示例：
[root@Mysql /]tree /data /data |-- 3306 | |--data 《==3306实例的数据文件 | |--my.cnf 《==3306实例的配置文件 | |--mysql 《==3306实例的启动文件 --3307 | |--data 《==3307实例的数据文件 | |--my.cnf 《==3307实例的配置文件 | |--mysql 《==3307实例的启动文件
Mysql多实例配置流程：
1.安装Msyql需要的依赖包 2.编译安装Mysql需要的软件 3.开始安装Mysql 4.配置多实例 5.初始化Mysql数据库 6.启动Mysql 7.登录mysql 8.故障排除说明 9.开机自启动
Mysql多实例数据库安装
1.安装Msyql需要的依赖包
yum install ncurses-devel libaio-devel -y rpm -qa ncurses-devel libaio-devel libaio-devel-0.3.107-10.e16x86_64 ncurses-devel-5.7-3.20090208.c16x86_64
数据库：
服务器名字 IP地址 host C3-Mysql数据库 172.16.1.52/24 db02
2.编译安装Mysql需要的软件
ls -lh cmake-2.8.8.tar.gz tar xf cmake-2.8.8.tar.gz cd cmake-2.8.8 ./configure gmake gmake install which cmake /usr/local/bin/cmake cd ../
或者也可以使用yum安装 (推荐yum安装)yum install cmake -y
3.开始安装Mysql
#创建mysql用户 useradd mysql -s /sbin/nologin -M id mysql #进入程序下载的路径 cd /home/oldboy/tools wget http://downloads.mysql.com/archives/get/file/mysql-5.5.32.tar.gz
Mysql源码包和二进制包名称
Mysql软件 软件名 Msyql源码安装包 mysql-5.5.32.tar.gz(本文使用的安装包) Mysql二进制安装包 mysql-5.5.32-linux-x86_64.tar.gz
#解压安装包
tar xf mysql-5.5.32.tar.gz cd mysql-5.5.32 [root@db02 mysql-5.5.32]# cmake . -DCMAKE_INSTALL_PREFIX=/application/mysql-5.5.32 \ -DMYSQL_DATADIR=/application/mysql-5.5.32/data \ -DMYSQL_UNIX_ADDR=/application/mysql-5.5.32/tmp/mysql.sock \ -DDEFAULT_CHARSET=utf8 \ -DDEFAULT_COLLATION=utf8_general_ci \ -DEXTRA_CHARSETS=gbk,gb2312,utf8,ascii \ -DENABLED_LOCAL_INFILE=ON \ -DWITH_INNOBASE_STORAGE_ENGINE=1 \ -DWITH_FEDERATED_STORAGE_ENGINE=1 \ -DWITH_BLACKHOLE_STORAGE_ENGINE=1 \ -DWITHOUT_EXAMPLE_STORAGE_ENGINE=1 \ -DWITHOUT_PARTITION_STORAGE_ENGINE=1 \ -DWITH_FAST_MUTEXES=1 \ -DWITH_ZLIB=bundled \ -DENABLED_LOCAL_INFILE=1 \ -DWITH_READLINE=1 \ -DWITH_EMBEDDED_SERVER=1 \ -DWITH_DEBUG=0 [root@db02 mysql-5.5.32]# make && make install [root@db02 mysql-5.5.32]# ln -s /application/mysql-5.5.32/ /application/mysql [root@db02 mysql-5.5.32]# cd /application/mysql [root@db02 mysql]# ls bin data include lib mysql-test scripts sql-bench COPYING docs INSTALL-BINARY man README share support-files
4.配置多实例
[root@db02 mysql]# mkdir -p /data/{3306,3307}/data [root@db02 ~]# tree /data/ /data/ ├── 3306 │ ├── data │ ├── my.cnf │ └── mysql └── 3307 ├── data ├── my.cnf └── mysql 4 directories, 4 files 3306文件夹说明：
####vim my.cnf####
[client] port = 3306 socket = /data/3306/mysql.sock [mysql] no-auto-rehash [mysqld] user = mysql port = 3306 socket = /data/3306/mysql.sock basedir = /application/mysql datadir = /data/3306/data open_files_limit = 1024 back_log = 600 max_connections = 800 max_connect_errors = 3000 table_cache = 614 external-locking = FALSE max_allowed_packet =8M sort_buffer_size = 1M join_buffer_size = 1M thread_cache_size = 100 thread_concurrency = 2 query_cache_size = 2M query_cache_limit = 1M query_cache_min_res_unit = 2k #default_table_type = InnoDB thread_stack = 192K #transaction_isolation = READ-COMMITTED tmp_table_size = 2M max_heap_table_size = 2M long_query_time = 1 #log_long_format #log-error = /data/3306/error.log #log-slow-queries = /data/3306/slow.log pid-file = /data/3306/mysql.pid log-bin = /data/3306/mysql-bin relay-log = /data/3306/relay-bin relay-log-info-file = /data/3306/relay-log.info binlog_cache_size = 1M max_binlog_cache_size = 1M max_binlog_size = 2M expire_logs_days = 7 key_buffer_size = 16M read_buffer_size = 1M read_rnd_buffer_size = 1M bulk_insert_buffer_size = 1M #myisam_sort_buffer_size = 1M #myisam_max_sort_file_size = 10G #myisam_max_extra_sort_file_size = 10G #myisam_repair_threads = 1 #myisam_recover lower_case_table_names = 1 skip-name-resolve slave-skip-errors = 1032,1062 replicate-ignore-db=mysql server-id = 1 innodb_additional_mem_pool_size = 4M innodb_buffer_pool_size = 32M innodb_data_file_path = ibdata1:128M:autoextend innodb_file_io_threads = 4 innodb_thread_concurrency = 8 innodb_flush_log_at_trx_commit = 2 innodb_log_buffer_size = 2M innodb_log_file_size = 4M innodb_log_files_in_group = 3 innodb_max_dirty_pages_pct = 90 innodb_lock_wait_timeout = 120 innodb_file_per_table = 0 [mysqldump] quick max_allowed_packet = 2M [mysqld_safe] log-error=/data/3306/mysql_oldboy3306.err pid-file=/data/3306/mysqld.pid
####vim mysql####
#!/bin/sh ################################################ #this scripts is created by liuliya at 2016-12-09 #oldboy QQ:865205026 #site:http://www.liuliya.com ################################################ #init port=3306 mysql_user="root" mysql_pwd="oldboy" CmdPath="/application/mysql/bin" mysql_sock="/data/${port}/mysql.sock" #startup function function_start_mysql() { if [ ! -e "$mysql_sock" ];then printf "Starting MySQL...\n" /bin/sh ${CmdPath}/mysqld_safe --defaults-file=/data/${port}/my.cnf 2>&1 > /dev/null & else printf "MySQL is running...\n" exit fi } #stop function function_stop_mysql() { if [ ! -e "$mysql_sock" ];then printf "MySQL is stopped...\n" exit else printf "Stoping MySQL...\n" ${CmdPath}/mysqladmin -u ${mysql_user} -p${mysql_pwd} -S /data/${port}/mysql.sock shutdown fi } #restart function function_restart_mysql() { printf "Restarting MySQL...\n" function_stop_mysql sleep 2 function_start_mysql } case $1 in start) function_start_mysql ;; stop) function_stop_mysql ;; restart) function_restart_mysql ;; *) printf "Usage: /data/${port}/mysql {start|stop|restart}\n" esac 3307文件夹说明：
####vim my.cnf
[client] port = 3307 socket = /data/3307/mysql.sock [mysql] no-auto-rehash [mysqld] user = mysql port = 3307 socket = /data/3307/mysql.sock basedir = /application/mysql datadir = /data/3307/data open_files_limit = 1024 back_log = 600 max_connections = 800 max_connect_errors = 3000 table_cache = 614 external-locking = FALSE max_allowed_packet =8M sort_buffer_size = 1M join_buffer_size = 1M thread_cache_size = 100 thread_concurrency = 2 query_cache_size = 2M query_cache_limit = 1M query_cache_min_res_unit = 2k #default_table_type = InnoDB thread_stack = 192K #transaction_isolation = READ-COMMITTED tmp_table_size = 2M max_heap_table_size = 2M #long_query_time = 1 #log_long_format #log-error = /data/3307/error.log #log-slow-queries = /data/3307/slow.log pid-file = /data/3307/mysql.pid #log-bin = /data/3307/mysql-bin relay-log = /data/3307/relay-bin relay-log-info-file = /data/3307/relay-log.info binlog_cache_size = 1M max_binlog_cache_size = 1M max_binlog_size = 2M expire_logs_days = 7 key_buffer_size = 16M read_buffer_size = 1M read_rnd_buffer_size = 1M bulk_insert_buffer_size = 1M #myisam_sort_buffer_size = 1M #myisam_max_sort_file_size = 10G #myisam_max_extra_sort_file_size = 10G #myisam_repair_threads = 1 #myisam_recover lower_case_table_names = 1 skip-name-resolve slave-skip-errors = 1032,1062 replicate-ignore-db=mysql server-id = 3 innodb_additional_mem_pool_size = 4M innodb_buffer_pool_size = 32M innodb_data_file_path = ibdata1:128M:autoextend innodb_file_io_threads = 4 innodb_thread_concurrency = 8 innodb_flush_log_at_trx_commit = 2 innodb_log_buffer_size = 2M innodb_log_file_size = 4M innodb_log_files_in_group = 3 innodb_max_dirty_pages_pct = 90 innodb_lock_wait_timeout = 120 innodb_file_per_table = 0 [mysqldump] quick max_allowed_packet = 2M [mysqld_safe] log-error=/data/3307/mysql_oldboy3307.err pid-file=/data/3307/mysqld.pid
####vim mysql####
#!/bin/sh ################################################ #this scripts is created by liuliya at 2016-12-09 #oldboy QQ:865205026 #site:http://www.liuliya.com ################################################ #init port=3307 mysql_user="root" mysql_pwd="oldboy" CmdPath="/application/mysql/bin" mysql_sock="/data/${port}/mysql.sock" #startup function function_start_mysql() { if [ ! -e "$mysql_sock" ];then printf "Starting MySQL...\n" /bin/sh ${CmdPath}/mysqld_safe --defaults-file=/data/${port}/my.cnf 2>&1 > /dev/null & else printf "MySQL is running...\n" exit fi } #stop function function_stop_mysql() { if [ ! -e "$mysql_sock" ];then printf "MySQL is stopped...\n" exit else printf "Stoping MySQL...\n" ${CmdPath}/mysqladmin -u ${mysql_user} -p${mysql_pwd} -S /data/${port}/mysql.sock shutdown fi } #restart function function_restart_mysql() { printf "Restarting MySQL...\n" function_stop_mysql sleep 2 function_start_mysql } case $1 in start) function_start_mysql ;; stop) function_stop_mysql ;; restart) function_restart_mysql ;; *) printf "Usage: /data/${port}/mysql {start|stop|restart}\n" esac #为mysql启动命令增加执行权限find /data -type f -name "mysql"|xargs chmod +x
#更改/data目录的属组chwon -R mysql.mysql /data/
5.初始化Mysql数据库（mysql加载自身的管理的库和表）
[root@db02 ~]# cd /application/mysql/scripts/ [root@db02 scripts]# ls mysql_install_db
#3306实例初始化[root@db02 scripts]# ./mysql_install_db --basedir=/application/mysql --datadir=/data/3306/data --user=mysql
返回2个OK证明成功
#3307实例初始化[root@db02 scripts]# ./mysql_install_db --basedir=/application/mysql --datadir=/data/3307/data --user=mysql
返回2个OK证明成功
6.启动Mysql
[root@db02 scripts]# /data/3306/mysql start [root@db02 scripts]# /data/3307/mysql start
#查看端口netstat -lntup|grep 330
#配置mysql的环境变量cp /application/mysql/bin/* /usr/local/sbin/
#查看环境变量echo $PATH
7.登录mysql(需要制定sock)
mysql -S /data/3306/mysql.sock mysql -S /data/3307/mysql.sock
8.故障排除说明
1.查看日志cat mysql_oldboy3306.err
2.启动如果发现没有显示Msyql对应实例的端口，请稍微等待几秒在检查，Mysql服务的启动比Web等慢一些。
PS：经常查看各种服务运行日志是个很好的习惯，也是成为高手的必经之路。
9.开机自启动
具体命令：
echo "//mysql mutil instances" >>/etc/rc.local echo "/data/3306/mysql start" >>/etc/rc.local echo "/data/3307/mysql start" >>/etc/rc.local
如何增加一个mysql实例
具体命令集合：
mkdir -p /data/3308/data \cp /data/3306/my.cnf /data/3308/ \cp /data/3306/mysql /data/3308/ cd 3308/ sed -i 's/3306/3308/g' /data/3308/my.cnf sed -i 's/server-id = 1/server-id = 8/g' /data/3308/my.cnf sed -i 's/3306/3308/g' /data/3308/mysql chown -R mysql.mysql /data/3308 chmod 700 /data/3308/mysql
#初始化3308 实例Mysql数据库
[root@db02 ~]# cd /application/mysql/scripts/
#3306实例初始化[root@db02 scripts]# ./mysql_install_db --basedir=/application/mysql --datadir=/data/3308/data --user=mysql
#启动3308实例的数据库/data/3308/mysql start