什么是MySQL集群，什么是MySQL集群，如果你想知道什么是MySQL集群，我现在就带你研究。
MySQL 是一款流行的轻量级数据库，很多应用都是使用它作为数据存储。作为小型应用的数据库，它完全可以胜任，但是如果是大型应用，高性能高可用的要求，单服务器部署的MySQL就不够了。MySQL NDB Cluster 为这个需求提供了一个官方的集群解决方案。
MySQL NDB Cluster 是什么
MySQL NDB Cluster 是 MySQL 的一个高可用、高冗余版本，适用于分布式计算环境。文档链接
搭建集群的前置工作
至少准备 3 台服务器，一台作为管理服务器，两台作为数据服务器和 SQL 服务器，当然有更多的服务器会更好。
管理服务器mgm：192.168.0.105 数据服务器ndb1：192.168.0.106 数据服务器ndb2：192.168.0.104 sql服务器：192.168.0.106 sql服务器：192.168.0.104
本文以 ubuntu20.04 为例，所有操作都可用于 ubuntu 系统。
开始部署集群
首先下载 MySQL NDB Cluster二进制文件，解压缩后开始下面的步骤。
部署管理服务器#
更新系统
apt update -y && apt upgrade -y && apt install libncurses5 -y
复制 ndb_mgm 和 ndb_mgmd 到管理服务器
scp ./mysql-cluster-gpl-7.6.17-linux-glibc2.12-x86_64/bin/ndb_mgm* mgm@192.168.0.105:/home/mgm
在管理服务器复制 ndb_mgm 和 ndb_mgmd 到/usr/local/bin 文件夹
cp -rfv /home/mgm/ndb_mgm* /usr/local/bin
赋予 ndb_mgm 和 ndb_mgmd 可执行权限
chmod +x /usr/local/bin/ndb_mgm*
添加配置文件
mkdir /var/lib/mysql-cluster vi /var/lib/mysql-cluster/config.ini
config.ini
[ndbd default]
Options affecting ndbd processes on all data nodes:
NoOfReplicas=2 # Number of fragment replicas DataMemory=98M # How much memory to allocate for data storage
[ndb_mgmd]
Management process options:
HostName=192.168.0.105 # Hostname or IP address of management node NodeId=1 # Node ID for this Management node DataDir=/var/lib/mysql-cluster # Directory for management node log files
[ndbd]
Options for data node "A":
# (one [ndbd] section per data node)
HostName=192.168.0.104 # Hostname or IP address NodeId=2 # Node ID for this data node DataDir=/data/mysql-cluster/data # Directory for this data node's data files
[ndbd]
Options for data node "B”:
# (one [ndbd] section per data node)
HostName=192.168.0.106 # Hostname or IP address NodeId=3 # Node ID for this data node DataDir=/data/mysql-cluster/data # Directory for this data node's data files
[mysqld]
SQL node options:
HostName=192.168.0.104 # Hostname or IP address # (additional mysqld connections can be # specified for this node for various # purposes such as running ndb_restore)
[mysqld]
SQL node options:
HostName=192.168.0.106 # Hostname or IP address # (additional mysqld connections can be # specified for this node for various # purposes such as running ndb_restore)
开启防火墙，集群管理服务默认使用 1186 端口
ufw allow 22 ufw allow 1186 ufw enable
初始化并启动管理服务器
cd /usr/local/bin/ ndb_mgmd --initial --configdir=/var/lib/mysql-cluster -f /var/lib/mysql-cluster/config.ini --ndb-nodeid=1
当出现以下结果的时候，表示管理服务器已经启动成功了
root@mgm:/usr/local/bin# ndb_mgmd --initial --configdir=/var/lib/mysql-cluster -f /var/lib/mysql-cluster/config.ini --ndb-nodeid=1 MySQL Cluster Management Server mysql-5.7.33 ndb-7.6.17
我们再执行 ndb_mgm 命令，可以查看当前集群的状态
root@mgm:/usr/local/bin# ndb_mgm -- NDB Cluster -- Management Client -- ndb_mgm> show Connected to Management Server at: localhost:1186 Cluster Configuration
[ndbd(NDB)] 2 node(s) id=2 (not connected, accepting connect from 192.168.0.104) id=3 (not connected, accepting connect from 192.168.0.106)
[ndb_mgmd(MGM)] 1 node(s) id=1 @192.168.0.105 (mysql-5.7.33 ndb-7.6.17)
[mysqld(API)] 2 node(s) id=4 (not connected, accepting connect from 192.168.0.104) id=5 (not connected, accepting connect from 192.168.0.106)
部署数据服务器#
在所有数据服务器上执行以下操作
更新系统
apt update -y && apt upgrade -y && apt install libncurses5 -y
开启防火墙
ufw allow 22 ufw allow 2202 ufw enable
复制 ndbd 和 ndbmtd 到数据服务器
#复制到192.168.0.106 scp ./mysql-cluster-gpl-7.6.17-linux-glibc2.12-x86_64/bin/ndbd ndb1@192.168.0.106:/home/ndb1 scp ./mysql-cluster-gpl-7.6.17-linux-glibc2.12-x86_64/bin/ndbmtd ndb1@192.168.0.106:/home/ndb1
#复制到192.168.0.104 scp ./mysql-cluster-gpl-7.6.17-linux-glibc2.12-x86_64/bin/ndbd ndb2@192.168.0.104:/home/ndb2 scp ./mysql-cluster-gpl-7.6.17-linux-glibc2.12-x86_64/bin/ndbmtd ndb2@192.168.0.104:/home/ndb2
在管理服务器复制 ndbd 和 ndbmtd 到/usr/local/bin 文件夹
#192.168.0.106 cp -rfv /home/ndb1/ndbd /usr/local/bin cp -rfv /home/ndb1/ndbmtd /usr/local/bin
#192.168.0.104 cp -rfv /home/ndb2/ndbd /usr/local/bin cp -rfv /home/ndb2/ndbmtd /usr/local/bin
赋予 ndbd 可执行权限
chmod +x /usr/local/bin/ndbd chmod +x /usr/local/bin/ndbmtd
在/etc下加入my.cnf文件
vi /etc/my.cnf
my.cnf文件
[mysqld]
Options for mysqld process:
ndbcluster # run NDB storage engine
[mysql_cluster]
Options for NDB Cluster processes:
ndb-connectstring=192.168.0.105 # location of management server
创建数据保存的目录，必须与管理服务配置的路径一致
mkdir -p /data/mysql-cluster/data
启动数据服务
root@ndb1:/usr/local/bin# ndbd 2021-06-20 08:10:23 [ndbd] INFO -- Angel connected to '192.168.0.105:1186' 2021-06-20 08:10:23 [ndbd] INFO -- Angel allocated nodeid: 3
回到集群管理服务器查看集群状态，此时可以看到数据服务已经连接成功
root@mgm:/usr/local/bin# ndb_mgm -- NDB Cluster -- Management Client -- ndb_mgm> show Connected to Management Server at: localhost:1186 Cluster Configuration
[ndbd(NDB)] 2 node(s) id=2 (not connected, accepting connect from 192.168.0.104) id=3 @192.168.0.106 (mysql-5.7.33 ndb-7.6.17, starting, Nodegroup: 0)
[ndb_mgmd(MGM)] 1 node(s) id=1 @192.168.0.105 (mysql-5.7.33 ndb-7.6.17)
[mysqld(API)] 2 node(s) id=4 (not connected, accepting connect from 192.168.0.104) id=5 (not connected, accepting connect from 192.168.0.106)
在另一台服务器（192.168.0.104）重复 4、5、6、7 步骤的操作，结果可看到
root@ndb2:/usr/local/bin# ndbd 2021-06-20 08:20:10 [ndbd] INFO -- Angel connected to '192.168.0.105:1186' 2021-06-20 08:20:10 [ndbd] INFO -- Angel allocated nodeid: 2
回到集群管理服务器查看集群状态，此时可以看到所有数据服务已经连接成功
root@mgm:/usr/local/bin# ndb_mgm -- NDB Cluster -- Management Client -- ndb_mgm> show Connected to Management Server at: localhost:1186 Cluster Configuration
[ndbd(NDB)] 2 node(s) id=2 @192.168.0.104 (mysql-5.7.33 ndb-7.6.17, Nodegroup: 0, *) id=3 @192.168.0.106 (mysql-5.7.33 ndb-7.6.17, Nodegroup: 0)
[ndb_mgmd(MGM)] 1 node(s) id=1 @192.168.0.105 (mysql-5.7.33 ndb-7.6.17)
[mysqld(API)] 2 node(s) id=4 (not connected, accepting connect from 192.168.0.104) id=5 (not connected, accepting connect from 192.168.0.106)
在目录/data/mysql/data下面可以看到数据服务已经产生了数据
root@ndb1:~# ls /data/mysql/data/ ndb_3_fs ndb_3_out.log ndb_3.pid
部署 SQL 服务#
复制 MySQL 到SQL服务器
scp ./mysql-cluster-gpl-7.6.17-linux-glibc2.12-x86_64.tar.gz ndb2@192.168.0.104:/home/ndb2 scp ./mysql-cluster-gpl-7.6.17-linux-glibc2.12-x86_64.tar.gz ndb1@192.168.0.106:/home/ndb1
解压缩 MySQL, 然后复制到/usr/local目录
tar -zxvf mysql-cluster-gpl-7.6.17-linux-glibc2.12-x86_64.tar.gz cp -rfv mysql-cluster-gpl-7.6.17-linux-glibc2.12-x86_64 /usr/local/ ln -snf /usr/local/mysql-cluster-gpl-7.6.17-linux-glibc2.12-x86_64 /usr/local/mysql
cp /usr/local/mysql/support-files/mysql.server /etc/init.d/mysql.server export PATH=$PATH:/usr/local/mysql/bin source /etc/profile
开启防火墙
ufw allow 22 ufw allow 3306 ufw enable
创建 MySQL 数据存放的目录
mkdir -p /data/mysql/data mkdir -p /data/mysql/run mkdir -p /var/log/mysql
创建 mysql 用户，创建相关目录
groupadd mysql useradd -r -g mysql -s /bin/false mysql chown mysql:mysql /data/mysql/data chmod 750 /data/mysql/data
chown mysql:mysql /data/mysql/run chmod 750 /data/mysql/run
chown mysql:mysql /var/log/mysql chmod 750 /var/log/mysql
创建 MySQL 配置文件
mkdir -p /etc/mysql vi /etc/mysql/my.cnf
my.cnf
[mysqld]
Options for mysqld process:
ndbcluster # run NDB storage engine
pid-file = /data/mysql/run/mysqld.pid socket = /data/mysql/run/mysqld.sock datadir = /data/mysql/data
log-error = /var/log/mysql/error.log
By default we only accept connections from localhost
bind-address = 192.168.0.106
Disabling symbolic-links is recommended to prevent assorted security risks
symbolic-links = 0
[mysql_cluster]
Options for NDB Cluster processes:
ndb-connectstring = 192.168.0.105 # location of management server
[client] socket = /data/mysql/run/mysqld.sock
初始化MySQL
/usr/local/mysql/bin/mysqld --defaults-file=/etc/mysql/my.cnf --initialize --user=mysql --basedir=/usr/local/mysql
记录下 MySQL 初始化生成的 root 用户密码 sF#Hy,IuT6d#
root@ndb1:~# /usr/local/mysql/bin/mysqld --defaults-file=/etc/mysql/my.cnf --initialize --user=mysql --basedir=/usr/local/mysql 2021-06-20T12:23:26.874302Z 0 [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details). 2021-06-20T12:23:27.102146Z 0 [Warning] InnoDB: New log files created, LSN=45790 2021-06-20T12:23:27.145317Z 0 [Warning] InnoDB: Creating foreign key constraint system tables. 2021-06-20T12:23:27.154405Z 0 [Warning] No existing UUID has been found, so we assume that this is the first time that this server has been started. Generating a new UUID: 50a15854-d1c2-11eb-9792-000c29681e23. 2021-06-20T12:23:27.155927Z 0 [Warning] Gtid table is not ready to be used. Table 'mysql.gtid_executed' cannot be opened. 2021-06-20T12:23:28.339372Z 0 [Warning] CA certificate ca.pem is self signed. 2021-06-20T12:23:28.624534Z 1 [Note] A temporary password is generated for root@localhost: sF#Hy,IuT6d#
启动MySQL
/usr/local/mysql/bin/mysqld_safe --user=mysql &
修改 root 用户密码
mysqladmin -uroot -p'sF#Hy,IuT6d#' password '123456'
回到集群管理服务器查看集群状态，此时可以看到有一个 SQL 服务已经连接上了
root@mgm:/usr/local/bin# ndb_mgm -- NDB Cluster -- Management Client -- ndb_mgm> show Connected to Management Server at: localhost:1186 Cluster Configuration
[ndbd(NDB)] 2 node(s) id=2 @192.168.0.104 (mysql-5.7.33 ndb-7.6.17, Nodegroup: 0, *) id=3 @192.168.0.106 (mysql-5.7.33 ndb-7.6.17, Nodegroup: 0)
[ndb_mgmd(MGM)] 1 node(s) id=1 @192.168.0.105 (mysql-5.7.33 ndb-7.6.17)
[mysqld(API)] 2 node(s) id=4 (not connected, accepting connect from 192.168.0.104) id=5 @192.168.0.106 (mysql-5.7.33 ndb-7.6.17)
在另一台服务器（192.168.0.104）部署 SQL 服务，回到集群管理服务器查看集群状态，此时可以看到所有 SQL 服务已经连接成功
root@mgm:/usr/local/bin# ndb_mgm -- NDB Cluster -- Management Client -- ndb_mgm> show Cluster Configuration
[ndbd(NDB)] 2 node(s) id=2 @192.168.0.104 (mysql-5.7.33 ndb-7.6.17, Nodegroup: 0, *) id=3 @192.168.0.106 (mysql-5.7.33 ndb-7.6.17, Nodegroup: 0)
[ndb_mgmd(MGM)] 1 node(s) id=1 @192.168.0.105 (mysql-5.7.33 ndb-7.6.17)
[mysqld(API)] 2 node(s) id=4 @192.168.0.104 (mysql-5.7.33 ndb-7.6.17) id=5 @192.168.0.106 (mysql-5.7.33 ndb-7.6.17)
所有集群服务部署完毕，我们来测试一下集群是否真的部署成功#
在 192.168.0.106 的 MySQL 上创建数据库和表
CREATE DATABASE wechat;
CREATE TABLE wechat.user (
Column1 varchar(100) NULL,
Column2 varchar(100) NULL
)
ENGINE=ndbcluster
DEFAULT CHARSET=utf8mb4
COLLATE=utf8mb4_general_ci;
插入数据并查看
mysql> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | mysql | | ndbinfo | | performance_schema | | sys | | wechat | +--------------------+ 6 rows in set (0.00 sec)
mysql> select * from wechat.user; Empty set (0.02 sec)
mysql> insert wechat.user (Column1, column2) value ('1', '2'); Query OK, 1 row affected (0.01 sec)
mysql> select * from wechat.user; +---------+---------+ | Column1 | Column2 | +---------+---------+ | 1 | 2 | +---------+---------+ 1 row in set (0.00 sec)
在另一个 SQL 服务器查询，结果是成功的
mysql> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | mysql | | ndbinfo | | performance_schema | | sys | | wechat | +--------------------+ 6 rows in set (0.00 sec)
mysql> select * from wechat.user; Empty set (0.07 sec)
mysql> select * from wechat.user; +---------+---------+ | Column1 | Column2 | +---------+---------+ | 1 | 2 | +---------+---------+ 1 row in set (0.00 sec)
现在我们把其中一个数据节点关掉，在管理服务器我们看到 ndbd已经关闭一个了
root@mgm:/usr/local/bin# ndb_mgm -- NDB Cluster -- Management Client -- ndb_mgm> show Connected to Management Server at: localhost:1186 Cluster Configuration
[ndbd(NDB)] 2 node(s) id=2 @192.168.0.104 (mysql-5.7.33 ndb-7.6.17, Nodegroup: 0, *) id=3 (not connected, accepting connect from 192.168.0.106)
[ndb_mgmd(MGM)] 1 node(s) id=1 @192.168.0.105 (mysql-5.7.33 ndb-7.6.17)
[mysqld(API)] 2 node(s) id=4 @192.168.0.104 (mysql-5.7.33 ndb-7.6.17) id=5 @192.168.0.106 (mysql-5.7.33 ndb-7.6.17)
写入一笔数据
mysql> select * from wechat.user; +---------+---------+ | Column1 | Column2 | +---------+---------+ | 1 | 2 | +---------+---------+ 1 row in set (0.01 sec)
mysql> insert into wechat.user (Column1, column2) value ('3', '4'); Query OK, 1 row affected (0.00 sec)
mysql> select * from wechat.user; +---------+---------+ | Column1 | Column2 | +---------+---------+ | 3 | 4 | | 1 | 2 | +---------+---------+ 2 rows in set (0.00 sec)
在另一台 SQL 服务器查询，结果还是一致的
mysql> select * from wechat.user; +---------+---------+ | Column1 | Column2 | +---------+---------+ | 3 | 4 | | 1 | 2 | +---------+---------+ 2 rows in set (0.00 sec)
我们再关闭 192.168.0.106 SQL服务
root@mgm:/usr/local/bin# ndb_mgm -- NDB Cluster -- Management Client -- ndb_mgm> show Connected to Management Server at: localhost:1186 Cluster Configuration
[ndbd(NDB)] 2 node(s) id=2 @192.168.0.104 (mysql-5.7.33 ndb-7.6.17, Nodegroup: 0, *) id=3 (not connected, accepting connect from 192.168.0.106)
[ndb_mgmd(MGM)] 1 node(s) id=1 @192.168.0.105 (mysql-5.7.33 ndb-7.6.17)
[mysqld(API)] 2 node(s) id=4 @192.168.0.104 (mysql-5.7.33 ndb-7.6.17) id=5 (not connected, accepting connect from 192.168.0.106)
在 192.168.0.104 的 SQL 服务写入一笔数据
mysql> insert into wechat.user (Column1, column2) value ('5', '6'); Query OK, 1 row affected (0.00 sec)
mysql> select * from wechat.user; +---------+---------+ | Column1 | Column2 | +---------+---------+ | 5 | 6 | | 3 | 4 | | 1 | 2 | +---------+---------+ 3 rows in set (0.00 sec)
启动 192.168.0.106 的数据服务和SQL服务
root@mgm:/usr/local/bin# ndb_mgm -- NDB Cluster -- Management Client -- ndb_mgm> show Connected to Management Server at: localhost:1186 Cluster Configuration
[ndbd(NDB)] 2 node(s) id=2 @192.168.0.104 (mysql-5.7.33 ndb-7.6.17, Nodegroup: 0, *) id=3 @192.168.0.106 (mysql-5.7.33 ndb-7.6.17, Nodegroup: 0)
[ndb_mgmd(MGM)] 1 node(s) id=1 @192.168.0.105 (mysql-5.7.33 ndb-7.6.17)
[mysqld(API)] 2 node(s) id=4 @192.168.0.104 (mysql-5.7.33 ndb-7.6.17) id=5 @192.168.0.106 (mysql-5.7.33 ndb-7.6.17)
在 192.168.0.106 查询数据库发现，发生故障期间产生的数据已经同步了过来
root@ndb1:~# mysql -uroot -p Enter password: Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 4 Server version: 5.7.33-ndb-7.6.17-cluster-gpl MySQL Cluster Community Server (GPL)
Copyright (c) 2000, 2021, Oracle and/or its affiliates.
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> select * from wechat.user; +---------+---------+ | Column1 | Column2 | +---------+---------+ | 1 | 2 | | 5 | 6 | | 3 | 4 | +---------+---------+ 3 rows in set (0.08 sec)
数据库集群部署成功了，总结一下集群的注意事项#
创建表的时候，需要设置ENGINE=ndbcluster，具体请看上面的建表脚本。
每个 SQL 服务需要创建一样的用户密码
管理服务器不能全部发生故障，否则集群数据库操作失败。
数据服务器不能全部发生故障，否则集群数据库操作失败。
SQL 服务器发生故障期间建立的数据库，在恢复后不会自动同步新建数据库过来，需要手动在故障恢复后的服务器上创建同名数据库，之后数据才会自动同步过来。
只要管理服务器和数据服务器越多，故障发生时，才能保证数据安全的写入，才不会导致数据库系统不可用。
SQL 服务器越多，把数据库访问的请求通过负载均衡服务分摊到各个 SQL 服务器，才能承受更多的并发量。
集群启动必须按照以下顺序依次启动，管理服务->数据服务->SQL服务。
