MySQL-技术专题-主从复制原理

{"type":"doc","content":[{"type":"heading","attrs":{"align":null,"level":1},"content":[{"type":"text","text":"主从复制简介"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" 生产中，为了解决Mysql的单点故障已经提高MySQL的整体服务性能，一般都会采用"},{"type":"text","marks":[{"type":"strong"}],"text":"「主从复制」"},{"type":"text","text":"。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" 比如：在复杂的业务系统中，有一句sql执行后导致锁表，并且这条sql的的执行时间有比较长，那么此sql执行的期间导致服务不可用，这样就会严重影响用户的体验度。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" 主从复制中分为"},{"type":"text","marks":[{"type":"strong"}],"text":"「主服务器（master）"},{"type":"text","text":"「和」"},{"type":"text","marks":[{"type":"strong"}],"text":"从服务器（slave）」"},{"type":"text","text":"，"},{"type":"text","marks":[{"type":"strong"}],"text":"「主服务器负责写，而从服务器负责读」"},{"type":"text","text":"，Mysql的主从复制的过程是一个"},{"type":"text","marks":[{"type":"strong"}],"text":"「异步的过程」"},{"type":"text","text":"。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" 这样读写分离的过程能够是整体的服务性能提高，即使写操作时间比较长，也不影响读操作的进行。"}]},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"主从复制的原理"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" 首先放一张Mysql主从复制的原理图，总的来说Mysql的主从复制原理还是比较好理解的，原理非常的简单。"}]},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/0d/0d4f0dbbdfc3def676b0abb8c6898462.png","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":" "},{"type":"text","marks":[{"type":"color","attrs":{"color":"#F5222D","name":"red"}},{"type":"strong"}],"text":"Mysql的主从复制中主要有三个线程："},{"type":"codeinline","content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#F5222D","name":"red"}},{"type":"strong"}],"text":"master（binlog dump thread）、slave（I/O thread 、SQL thread）"}],"marks":[{"type":"color","attrs":{"color":"#F5222D","name":"red"}},{"type":"strong"}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#F5222D","name":"red"}},{"type":"strong"}],"text":"，Master一条线程和Slave中的两条线程。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" "},{"type":"codeinline","content":[{"type":"text","marks":[{"type":"strong"}],"text":"master（binlog dump thread）"}]},{"type":"text","marks":[{"type":"strong"}],"text":"主要负责Master库中有数据更新的时候，会按照"},{"type":"codeinline","content":[{"type":"text","marks":[{"type":"strong"}],"text":"binlog"}],"marks":[{"type":"strong"}]},{"type":"text","marks":[{"type":"strong"}],"text":"格式，将更新的事件类型写入到主库的"},{"type":"codeinline","content":[{"type":"text","marks":[{"type":"strong"}],"text":"binlog"}],"marks":[{"type":"strong"}]},{"type":"text","marks":[{"type":"strong"}],"text":"文件中"},{"type":"text","text":"。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" "},{"type":"text","marks":[{"type":"color","attrs":{"color":"#F5222D","name":"red"}},{"type":"strong"}],"text":" 并且，Master会创建"},{"type":"codeinline","content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#F5222D","name":"red"}},{"type":"strong"}],"text":"log dump"}],"marks":[{"type":"color","attrs":{"color":"#F5222D","name":"red"}},{"type":"strong"}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#F5222D","name":"red"}},{"type":"strong"}],"text":"线程通知Slave主库中存在数据更新，这就是为什么主库的binlog日志一定要开启的原因。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" "},{"type":"codeinline","content":[{"type":"text","text":"I/O thread"}]},{"type":"text","text":"线程在Slave中创建，该线程用于请求Master，Master会返回binlog的名称以及当前数据更新的位置、binlog文件位置的副本。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" 然后，将"},{"type":"codeinline","content":[{"type":"text","text":"binlog"}]},{"type":"text","text":"保存在 "},{"type":"text","marks":[{"type":"strong"}],"text":"「relay log（中继日志）」"},{"type":"text","text":" 中，中继日志也是记录数据更新的信息。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"SQL线程也是在Slave中创建的，当Slave检测到中继日志有更新，就会将更新的内容同步到Slave数据库中，这样就保证了主从的数据的同步。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" 以上就是主从复制的过程，当然，主从复制的过程有不同的策略方式进行数据的同步，主要包含以下几种："}]},{"type":"numberedlist","attrs":{"start":null,"normalizeStart":1},"content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":1,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#F5222D","name":"red"}},{"type":"strong"}],"text":"「同步策略」"},{"type":"text","marks":[{"type":"color","attrs":{"color":"#F5222D","name":"red"}}],"text":"：Master会等待所有的Slave都回应后才会提交，这个主从的同步的性能会严重的影响。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":2,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#F5222D","name":"red"}},{"type":"strong"}],"text":"「半同步策略」"},{"type":"text","marks":[{"type":"color","attrs":{"color":"#F5222D","name":"red"}}],"text":"：Master至少会等待一个Slave回应后提交。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":3,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#F5222D","name":"red"}},{"type":"strong"}],"text":"「异步策略」"},{"type":"text","marks":[{"type":"color","attrs":{"color":"#F5222D","name":"red"}}],"text":"：Master不用等待Slave回应就可以提交。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":4,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#F5222D","name":"red"}},{"type":"strong"}],"text":"「延迟策略」"},{"type":"text","marks":[{"type":"color","attrs":{"color":"#F5222D","name":"red"}}],"text":"：Slave要落后于Master指定的时间。"}]}]}]},{"type":"horizontalrule"},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" "},{"type":"text","marks":[{"type":"color","attrs":{"color":"#F5222D","name":"red"}},{"type":"strong"}],"text":"对于不同的业务需求，有不同的策略方案，但是一般都会采用最终一致性，不会要求强一致性，毕竟强一致性会严重影响性能。"}]},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"主从搭建"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" 下面我们就来实操搭建主从，使用的是两台centos7并且安装的是Mysql 8来搭建主从，有一台centos 7然后直接克隆就行了。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（1）首先检查centos 7里面的Mysql安装包和依赖包："}]},{"type":"codeblock","attrs":{"lang":null},"content":[{"type":"text","text":"rpm -qa |grep mysql"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" 执行后，在我本机上的显示如下："}]},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/19/192fd0fadf1e2e8591043620a937ad17.png","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（2）接着可以删除上面的安装包和依赖包："}]},{"type":"codeblock","attrs":{"lang":null},"content":[{"type":"text","text":"sudo yum remove mysql*"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（3）继续检查一下是否存在Mariadb，若是存在直接删除Mariadb"}]},{"type":"codeblock","attrs":{"lang":null},"content":[{"type":"text","text":"// 检查是否存在Mariadb\nrpm -qa |grep mariadb\n// 删除Mariadb\nsudo rpm -e --nodeps mariadb-libs-5.5.56-2.el7.x86_64"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（4）然后，就是删除Mysql的配置文件，可以使用下面的命令查找Msqyl配置文件的路径："}]},{"type":"codeblock","attrs":{"lang":null},"content":[{"type":"text","text":"sudo find / -name mysql"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在我本机上的显示的Mysql配置文件的路径如下："}]},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/2e/2ebb8d2b2ca54d878df1dd4ce61e25cf.png","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（5）然后，通过下面的命令，将他们逐一删除："}]},{"type":"codeblock","attrs":{"lang":null},"content":[{"type":"text","text":"sudo rm -rf /usr/lib64/mysql\n......"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（6）接着就开始安装Mysql 8了，使用wget命令下载Mysql 8的repo源，并且执行安装："}]},{"type":"codeblock","attrs":{"lang":null},"content":[{"type":"text","text":"wget https://repo.mysql.com//mysql80-community-release-el7-3.noarch.rpm\nsudo yum -y install mysql80-community-release-el7-3.noarch.rpm\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"安装完后会在/etc/yum.repos.d/目录下生成下面的两个文件，说明安装成功了："}]},{"type":"codeblock","attrs":{"lang":null},"content":[{"type":"text","text":"mysql-community.repo\nmysql-community-source.repo\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/0c/0c1bd5aba009a5e94fac32a67d49f10d.png","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"image"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（7）安装完Mysql8后，接着来更新一下yum源，并且查看yum仓库中的Mysql："}]},{"type":"codeblock","attrs":{"lang":null},"content":[{"type":"text","text":"// 更新yum源\nyum clean all\nyum makecache\n// 查看yum仓库中的Mysql\nyum list | grep mysql\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（8）可以查看到仓库中存在mysql-community-server.x86_64，直接安装就行了："}]},{"type":"codeblock","attrs":{"lang":null},"content":[{"type":"text","text":"sudo yum -y install mysql-community-server\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（9）接着启动Mysql，并检查Mysql的状态："}]},{"type":"codeblock","attrs":{"lang":null},"content":[{"type":"text","text":"// 启动Mysql\nsystemctl start mysqld.service\n// 检查Mysql的状态\nsystemctl status mysqld\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"确保查看Mysql的状态是"},{"type":"codeinline","content":[{"type":"text","text":"active(running)"}]},{"type":"text","text":"，表示正在运行，并且配置一下Mysql开机启动："}]},{"type":"codeblock","attrs":{"lang":null},"content":[{"type":"text","text":"systemctl enable mysqld\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/86/8661f9892165563e97f1e2b1e118e277.png","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"image"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（10）因为Mysql是新安装的，所以要修改一下初始密码，先查看一下初始密码："}]},{"type":"codeblock","attrs":{"lang":null},"content":[{"type":"text","text":"grep \"password\" /var/log/mysqld.log\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"你可能找出来有多个，可能是你之前安装卸载后的文件没有删干净，这里你就直接看时间，时间对应你现在的时间，就是你的初始密码："}]},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/e6/e600bbfab88219a4348f716cb44d00e4.png","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"image"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（11）然后使用初始密码，登陆数据库，并且修改密码："}]},{"type":"codeblock","attrs":{"lang":null},"content":[{"type":"text","text":"mysql -uroot -p\nALTER USER 'root'@'localhost' IDENTIFIED BY 'LDCldc@123095;\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（12）此时在创建一个可以用于给两一台centos连接的用户，默认的root用户只有本机才能连接："}]},{"type":"codeblock","attrs":{"lang":null},"content":[{"type":"text","text":"// 创建连接用户\ncreate user 'test'@'%' identified by 'LDCldc-2020';\n// 并且把防火墙给关了，或者配置一下3306端口\nsystemctl stop firewalld.service；\n// 设置防火墙开机自动关闭\nsystemctl disable firewalld.service；\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（13）测试：到这里就Mysql的安装教程就就讲完了，可以测试一下，两台centos是否可以ping通："}]},{"type":"codeblock","attrs":{"lang":null},"content":[{"type":"text","text":"ping 192.168.163.156\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/48/48d5c17cf67254d25bae4e3922d97209.png","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"image"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"我这里的两台机是可以互通的，"},{"type":"codeinline","content":[{"type":"text","text":"Master：192.168.163.156，Slave：192.168.163.155"}]},{"type":"text","text":"，并且Slave使用下面的命令可以登陆到Master的Mysql："}]},{"type":"codeblock","attrs":{"lang":null},"content":[{"type":"text","text":"mysql -u[user] -p[密码] -h[远程主机ip]"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"确保了这两项测试成功后，就可以进行下面的主从搭建了。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（14）我这里使用的使用两台centos 7的vmware的ip分别是"},{"type":"codeinline","content":[{"type":"text","text":"192.168.163.155（Slave）"}]},{"type":"text","text":"和"},{"type":"codeinline","content":[{"type":"text","text":"192.168.163.156（Master）"}]},{"type":"text","text":"作为测试，首先在192.168.163.156（Master）中创建一个测试库test："}]},{"type":"codeblock","attrs":{"lang":null},"content":[{"type":"text","text":"// 创建测试库\ncreate database test default character set utf8mb4 collate utf8mb4_general_ci;\n// 并且授权\ngrant all privileges on test.* to 'test'@'%';\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（15）然后编辑Master中的my.cnf文件，此文件位于/etc/my.cnf，执行下面的sql，并添加下面的信息："}]},{"type":"codeblock","attrs":{"lang":null},"content":[{"type":"text","text":"sudo vi /etc/my.cnf\n\n==========以下是配置文件中的信息=============\n# 配置编码为utf8\ncharacter_set_server=utf8mb4\ninit_connect='SET NAMES utf8mb4'\n\n# 配置要给Slave同步的数据库\nbinlog-do-db=test\n# 不用给Slave同步的数据库，一般是Mysql自带的数据库就不用给Slave同步了\nbinlog-ignore-db=mysql\nbinlog-ignore-db=information_schema\nbinlog-ignore-db=performance_schema\nbinlog-ignore-db=sys\n# 自动清理30天前的log文件\nexpire_logs_days=30\n# 启用二进制日志\nlog-bin=mysql-bin\n# Master的id，这个要唯一，唯一是值，在主从中唯一\nserver-id=3\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（16）配置完后重启Mysql服务，并查看Mysql的log_bin日志是否启动成功："}]},{"type":"codeblock","attrs":{"lang":null},"content":[{"type":"text","text":"systemctl restart mysqld\n# 查看log_bin日志是否启动成功\nshow variables like '%log_bin%';\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/0c/0c87c433f145a96dc7d3978fa046657b.png","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（17）接着查看Master的状态："}]},{"type":"codeblock","attrs":{"lang":null},"content":[{"type":"text","text":"show master status;"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/e2/e2a653a13ea54759e281ba2b55df9354.png","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"image"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"这两个数据"},{"type":"codeinline","content":[{"type":"text","text":"File"}]},{"type":"text","text":"和"},{"type":"codeinline","content":[{"type":"text","text":"Position"}]},{"type":"text","text":"要记住，后面配置Slave的时候要使用到这两个数据。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（18）最后登陆Master的数据库，并创建一个用户用于同步数据："}]},{"type":"codeblock","attrs":{"lang":null},"content":[{"type":"text","text":"create user 'backup'@'%' IDENTIFIED BY 'LDCldc-2020';\ngrant file on *.* to 'backup'@'%';\nGRANT REPLICATION SLAVE, REPLICATION CLIENT ON *.* to 'backup'@'%';\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"到这里Master的配置就配置完了，后面就进行Slave的配置。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（19）在Slave中同样要创建test数据库，并且授权给test用户："}]},{"type":"codeblock","attrs":{"lang":null},"content":[{"type":"text","text":"# 创建同步数据的test数据库\ncreate database test default character set utf8mb4 collate utf8mb4_general_ci;\n# 授权\ngrant all privileges on test.* to 'test'@'%';\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（20）接着编辑Slave中my.cnf文件，同样是在/etc/my.cnf路径下，加入如下配置："}]},{"type":"codeblock","attrs":{"lang":null},"content":[{"type":"text","text":"# 配置从服务器的ID，唯一的\nserver-id=4\n#加上以下参数可以避免更新不及时，SLAVE 重启后导致的主从复制出错。\nread_only = 1\nmaster_info_repository=TABLE\nrelay_log_info_repository=TABLE\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（21）并且重启Slave中的Mysql服务："}]},{"type":"codeblock","attrs":{"lang":null},"content":[{"type":"text","text":"systemctl restart mysqld\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（22）在Slave中添加Master的信息："}]},{"type":"codeblock","attrs":{"lang":null},"content":[{"type":"text","text":"# master_host是Master的ip，master_log_file和master_log_pos就是配置之前查看Master状态时显示的File和Position信息\nchange master to master_host='192.168.163.156',master_port=3306,master_user='backup',master_password='LDCldc-2020',master_log_file='mysql-bin.000001',master_log_pos=1513;\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（23）最后查看Slave的状态："}]},{"type":"codeblock","attrs":{"lang":null},"content":[{"type":"text","text":"show slave status\\G\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/2b/2ba2295e20f2b097d1d2d4cf3a0d459c.png","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"image"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"当看到"},{"type":"codeinline","content":[{"type":"text","text":"Slave_IO_Running"}]},{"type":"text","text":"和"},{"type":"codeinline","content":[{"type":"text","text":"Slave_SQL_Running"}]},{"type":"text","text":"都是yes的时候，这表示主从配置成功。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"「Slave_IO_Running也就是Slave中的IO线程用于请求Master，Slave_SQL_Running时sql线程将中继日志中更新日志同步到Slave数据库中。」"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"但是，有时候Slave_IO_Running会为no，而Slave_SQL_Running为yes，这时候需要检查一下原因，因为我自己初次搭建的时候，也是出现这个问题。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"首先看重启一下"},{"type":"codeinline","content":[{"type":"text","text":"Slave"}]},{"type":"text","text":"的MySQL服务："},{"type":"codeinline","content":[{"type":"text","text":"systemctl restart mysqld"}]},{"type":"text","text":"，然后执行："}]},{"type":"codeblock","attrs":{"lang":null},"content":[{"type":"text","text":"stop slave;\nstart slave;\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"这样就能够使"},{"type":"codeinline","content":[{"type":"text","text":"Slave_IO_Running"}]},{"type":"text","text":"和"},{"type":"codeinline","content":[{"type":"text","text":"Slave_SQL_Running"}]},{"type":"text","text":"显示都是yes了。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（24）最后就是测试了，测试使用的是之前创建的test库，Master是用来写的，在Master的test库中随机创建一个表，你会发现Slave也会有这个表，插入数据也一样，都会被同步到Slave中。"}]},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"主从面试"}]},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"❝"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Mysql主从有什么优点？为什么要选择主从？"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"❞"}]}]},{"type":"numberedlist","attrs":{"start":null,"normalizeStart":1},"content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":1,"align":null,"origin":null},"content":[{"type":"text","text":"高性能方面：主从复制通过水平扩展的方式，解决了原来单点故障的问题，并且原来的并发都集中到了一台Mysql服务器中，现在将单点负载分散到了多台机器上，实现读写分离，不会因为写操作过长锁表而导致读服务不能进行的问题，提高了服务器的整体性能。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":2,"align":null,"origin":null},"content":[{"type":"text","text":"可靠性方面：主从在对外提供服务的时候，若是主库挂了，会有通过主从切换，选择其中的一台Slave作为Master；若是Slave挂了，还有其它的Slave提供读服务，提高了系统的可靠性和稳定性。"}]}]}]},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"❝"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"若是主从复制，达到了写性能的瓶颈，你是怎么解决的呢？"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"❞"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"主从模式对于写少读多的场景确实非常大的优势，但是总会写操作达到瓶颈的时候，导致性能提不上去。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"这时候可以在设计上进行解决采用分库分表的形式，对于业务数据比较大的数据库可以采用分表，使得数据表的存储的数据量达到一个合理的状态。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"也可以采用分库，按照业务进行划分，这样对於单点的写，就会分成多点的写，性能方面也就会大大提高。"}]},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"❝"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"主从复制的过程有数据延迟怎么办？导致Slave被读取到的数据并不是最新数据。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"❞"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"主从复制有不同的复制策略，对于不同的场景的适应性也不同，对于数据的实时性要求很高，要求强一致性，可以采用同步复制策略，但是这样就会性能就会大打折扣。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"若是主从复制采用异步复制，要求数据最终一致性，性能方面也会好很多。只能说，对于数据延迟的解决方案没有最好的方案，就看你的业务场景中哪种方案使比较适合的。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}}]}