對(duì)于 MySQL 數(shù)據(jù)庫(kù)作為各個(gè)業(yè)務(wù)系統(tǒng)的存儲(chǔ)介質(zhì)，在系統(tǒng)中承擔(dān)著非常重要的職責(zé)，如果數(shù)據(jù)庫(kù)崩了，那么對(duì)于讀和寫(xiě)數(shù)據(jù)庫(kù)的操作都會(huì)受到影響。如果不能迅速恢復(fù)，對(duì)業(yè)務(wù)的影響是非常大的。之前 B 站不是出過(guò)一次事故么，2 小時(shí)才恢復(fù)過(guò)來(lái)，詳細(xì)可以看之前寫(xiě)的文章。
檢測(cè)和重啟：兩臺(tái)服務(wù)器上都部署 keepalived 軟件，定時(shí)檢測(cè) MySQL 服務(wù)是否正常，如果一個(gè)數(shù)據(jù)庫(kù)服務(wù)崩了，keepalived 會(huì)用腳本嘗試重啟 mysql 服務(wù)。
備份：兩個(gè) keepalived 服務(wù)都提供了虛擬 IP 供客戶端使用，但是流量只會(huì)轉(zhuǎn)到一臺(tái) MySQL 服務(wù)上。
虛擬 IP：keepalived 配置好了后，會(huì)有一個(gè) 虛擬 IP，對(duì)于客戶端來(lái)說(shuō)，不關(guān)心連接的是哪臺(tái) MySQL，訪問(wèn)虛擬 IP 就可以了。
流量切換：如果客戶端正在訪問(wèn)的 MySQL 服務(wù)崩了后，keepalived 會(huì)用我們寫(xiě)的腳本自動(dòng)重啟 MySQL，如果重啟失敗，腳本主動(dòng)停掉 keepalived，客戶端的流量就不會(huì)訪問(wèn)到這臺(tái)服務(wù)器上的 MySQL 服務(wù)，后續(xù)訪問(wèn)的流量都會(huì)切到另外一臺(tái) MySQL 服務(wù)。
檢測(cè)和重啟的原理如下所示：
需要配置的內(nèi)容如下：
兩臺(tái) Ubuntu 服務(wù)器上啟動(dòng) MySQL 容器。
配置 MySQL 主從復(fù)制架構(gòu)。
將 MySQL 主從改為主主復(fù)制架構(gòu)。
兩臺(tái)服務(wù)器搭建 keepalived 環(huán)境監(jiān)控 MySQL 和自動(dòng)重啟 MySQL。
二、主主復(fù)制的原理
對(duì)于 MySQL 的主主架構(gòu)，其實(shí)原理就是兩臺(tái)服務(wù)器互為主從，雙向復(fù)制。而復(fù)制的原理如下：
重新查詢客戶端的連接信息，發(fā)現(xiàn)已經(jīng)切換到 92b （node1）機(jī)器上的 mysql 了。
SHOW VARIABLES LIKE '%hostname%'
再次查看 node1 上 keepalived 上的狀態(tài)，再發(fā)送信息給
sudo systemctl status keepalived
七、遇到的坑
7.1 密碼不正確，無(wú)法登錄的問(wèn)題
密碼不正確，設(shè)置跳過(guò)密碼驗(yàn)證
apt-get update
apt install vim
修改 mysql 配置文件
vim /etc/mysql/my.cnf
添加一行配置，跳過(guò) mysql 密碼驗(yàn)證
skip-grant-tables
重啟容器
docker restart 9e6
重新計(jì)入 mysql 容器，連接 mysql，不需要密碼就可以連接上 mysql。
mysql
修改登錄密碼
update mysql.user set authentication_string=PASSWORD('123456') where User='root';
重啟容器
7.2 沒(méi)有映射 mysql 文件夾
cd /home/hss/mysql/etc sudo chmod 777 mysql -R
拷貝 mysql 文件夾
7.3 mysql data 文件夾沒(méi)有權(quán)限
sudo chmod 777 /home/hss/mysql/data -R
7.4 安裝依賴(lài)包失敗
sudo apt-get install -y libnl-dev libnl-3-dev libnl-genl-3.dev Reading package lists... Done Building dependency tree Reading state information... Done Note, selecting 'libnl-genl-3-dev'for regex 'libnl-genl-3.dev' Package libnl-dev is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source
E: Package 'libnl-dev' has no installation candidate
解決方案：更新包
sudo apt-get -y update
7.5 更新包失敗
Err:15 https://download./linux/ubuntu bionic Release
Could not wait for server fd - select (11: Resource temporarily unavailable) [IP: 198.18.0.39 443]
Reading package lists... Done
E: The repository 'https://download./linux/ubuntu bionic Release' no longer has a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
解決方案：
修改配置文件
sudo mv /etc/apt/sources.list /etc/apt/sources.list.backup sudo vim /etc/apt/sources.list
配置內(nèi)容如下：
deb http://archive./ubuntu/ trusty main restricted universe multiverse deb http://archive./ubuntu/ trusty-security main restricted universe multiverse deb http://archive./ubuntu/ trusty-updates main restricted universe multiverse deb http://archive./ubuntu/ trusty-proposed main restricted universe multiverse deb http://archive./ubuntu/ trusty-backports main restricted universe multiverse
執(zhí)行更新
sudo apt-get update
依賴(lài)包版本太高
apt-get install libnl-dev
The following packages have unmet dependencies: libnl-3-dev : Depends: libnl-3-200 (= 3.2.21-1ubuntu4.1) but 3.2.29-0ubuntu3 is to be installed Conflicts: libnl-dev but 1.1-8ubuntu1 is to be installed libnl-genl-3-dev : Depends: libnl-genl-3-200 (= 3.2.21-1ubuntu4.1) but 3.2.29-0ubuntu3 is to be installed E: Unable to correct problems, you have held broken packages.
root@node1:/usr/local/keepalived/etc/keepalived# service keepalived restart Failed to restart keepalived.service: Unit keepalived.service is masked. root@node1:/usr/local/keepalived/etc/keepalived# systemctl status keepalived.service ● keepalived.service Loaded: masked (/dev/null; bad) Active: inactive (dead) Condition: start condition failed at Wed 2022-05-11 02:40:46 UTC; 1 day 3h ago
WARNING - default user 'keepalived_script'for script execution does not exist - please create.
解決方案：
配置文件的 global_defs 配置里面增加 script_user root
global_defs { script_user rot }
執(zhí)行腳本失敗
May 16 03:50:54 node1 Keepalived_vrrp[19855]: WARNING - script '/usr/local/keepalived/restart_mysql.sh' is not executable for uid:gid 0:0 - disabling. May 16 03:50:54 node1 Keepalived_vrrp[19855]: SECURITY VIOLATION - scripts are being executed but script_security not enabled.
使用上面的兩個(gè)命令，我們可以判斷當(dāng)前的復(fù)制情況。
