案例
Nginx + Keepalived 案例
使用 Nginx + Keepalived 实现一个 web 服务高可用方案
架构图如下:
Nginx 的安装与配置
安装软件 # 安装nginx以及拓展源
yum install epel-release -y
yum install -y nginx
Nginx 配置 web 站点 #web1
[root@nginx1 ~]# vi /etc/nginx/conf.d/web.conf
server{
listen 8080;
root /usr/share/nginx/html;
index test.html;
}
[root@nginx1 ~]# echo "
This is web1
" > /usr/share/nginx/html/test.html#web2
[root@nginx2 ~]# vi /etc/nginx/conf.d/web.conf
server{
listen 8080;
root /usr/share/nginx/html;
index test.html;
}
[root@nginx2 ~]# echo "
This is web2
" > /usr/share/nginx/html/test.html启动 Nginx nginx -t
nginx
Keepalived 的安装与配置
安装 Keepalived yum install -y keepalived
配置 Keepalived(不同角色有些选项不一样:state 和 priority 配置项) web1:master vi /etc/keepalived/keepalived.conf
! Configuration File for keepalived
global_defs {
router_id LVS_DEVEL_1
}
vrrp_script nginx_check {
script "/tools/nginx_check.sh"
interval 1
}
vrrp_instance VI_1 {
state MASTER
#nopreempt
interface ens33
virtual_router_id 52
priority 100
advert_int 1
authentication {
auth_type PASS
auth_pass test
}
virtual_ipaddress {
192.168.149.100
}
track_script {
nginx_check
}
notify_master /tools/master.sh
notify_backup /tools/backup.sh
notify_fault /tools/fault.sh
notify_stop /tools/stop.sh
}
web2:slave vi /etc/keepalived/keepalived.conf
! Configuration File for keepalived
global_defs {
router_id LVS_DEVEL_2
}
vrrp_script nginx_check {
script "/tools/nginx_check.sh"
interval 1
}
vrrp_instance VI_1 {
state BACKUP
#nopreempt
interface ens33
virtual_router_id 52
priority 90
advert_int 1
authentication {
auth_type PASS
auth_pass test
}
virtual_ipaddress {
192.168.149.100
}
track_script {
nginx_check
}
notify_master /tools/master.sh
notify_backup /tools/backup.sh
notify_fault /tools/fault.sh
notify_stop /tools/stop.sh
}
编写相关脚本 编写 Keepalived 日志脚本(将每次工作过程输出到日志上) # 将所有脚本放在同一个目录下,方便集中管理
mkdir /tools && cd /tools
cat > master.sh << 'EOF'
ip=$(hostname -I | awk '{print $1}')
dt=$(date +'%Y%m%d %H:%M:%S')
echo "$0--${ip}--${dt}" >> /tmp/kp.log
EOF
cat > backup.sh << 'EOF'
ip=$(hostname -I | awk '{print $1}')
dt=$(date +'%Y%m%d %H:%M:%S')
echo "$0--${ip}--${dt}" >> /tmp/kp.log
EOF
cat > fault.sh << 'EOF'
ip=$(ip addr|grep inet| grep 192.168 |awk '{print $2}')
dt=$(date +'%Y%m%d %H:%M:%S')
echo "$0--${ip}--${dt}" >> /tmp/kp.log
EOF
cat > stop.sh << 'EOF'
ip=$(ip addr|grep inet| grep 192.168| awk '{print $2}')
dt=$(date +'%Y%m%d %H:%M:%S')
echo "$0--${ip}--${dt}" >> /tmp/kp.log
EOF
编写健康检查脚本 该脚本对 Nginx 进程进行检测,如果发现 Nginx 进程没了则返回失败(1) cat > nginx_check.sh << 'EOF'
#!/bin/bash
result=`pidof nginx`
if [ ! -z "${result}" ];
then exit 0
else exit 1
fi
EOF
编写完脚本后对这些脚本加 x 权限,并启动 Keepalived cd /tools/ && chmod +x *.sh
systemctl restart keepalived.service
验证
访问 VIP 地址 现在 web1(192.168.149.130)是 master 访问 192.168.149.100:8080,可以看到访问成功了 切换主备 关闭 web1 服务 [root@nginx1 ~]# nginx -s stop
然后再 web2 服务的主机可以看到 web2(192.168.149.131)获得了 VIP,升级成了主 访问 VIP 地址(192.168.149.100:8080),可以发现访问到了 web2 服务器上 之后重启 web1 看一下 可以看到 web1 主机又变成了 master,因为没有配置抢占模式/非抢占模式,所以选举机制是优先级,web1 的优先级比 web2 要高,所以 web1 启动后就会把 master 角色拿过来
问题解决
查看 keepalived 系统日志:less /var/log/messages
Unable to access script /shell/nginx_check.sh selinux 禁止了这个脚本。keepalived 进程的安全上下文与脚本的安全上下文不一致,就算有 rwx 权限也无法执行
最简单的解决方案就是关闭 selinux 功能: # 永久关闭 selinux
sed -i "s\SELINUX=enforcing\SELINUX=disabled\g" /etc/selinux/config
# 重启主机
reboot
# 临时关闭selinux,reboot服务器后失效
etenforce 0
解决方案2:将脚本转移到 /usr/libexec/keepalived 目录中 这个目录的安全上下文是 keepalived_unconfined_script_exec_t,与 keepalived 进程的安全上下文一致 解决方案3:修改 check.sh 的安全上下文为 keepalived 进程的安全上下文 chcon -t keepalived_unconfined_sript_exec_it /etc/keepalived/nginx_check.sh
keepalived_unconfined_script_exec_t 是一个在 SELinux 中用于标识 Keepalived 执行未限制脚本的上下文 这个上下文允许 Keepalived 进程在执行脚本时绕过一些 SELinux 限制,从而可以在需要的情况下执行脚本 # 查看 keepalived 进程的安全上下文
ps -eZ | grep keepalived
#输出:system_u:system_r:keepalived_t:s0 19689 ? 00:00:00 keepalived
# 查看文件/目录的安全上下文
ll -Z /etc/keepalived/check.sh
#输出:-rwr-xr-x. root system_u:object_r:etc_t:s0
Disabling track script chk_nginx since not found 在 VRRP 实例中添加 track_script { chk_nginx } 以启动脚本检测 warning default user ‘keepalived_script’for script execution does not exist - please create 找不到 keepalived_script 这个用户组,开启下面的配置,如果找不到就使用 root 在全局配置 global_defs 中添加 script_user root 注:该配置非必需,日志打印也只是警告而已 SECURITY VIOLATION - scripts are being executed but script_security notenabled 在全局配置 global_defs 中添加 enable_script_security Unknown keyword:’}’、‘track_script{’、'chk_nginx 等等 配置文件格式不正确:使用到大括号 { 的地方,确保正文与大括号间有空格。 Can't open PID file /var/run/nginx.pid (yet?) after start: No such fileor directory 使用 systemctl start nginx 时,先调用的是 nginx.service,启动时 nginx.pid 文件并未生成 在 /usr/lib/systemd/system/nginx.service 中 [service] 模块下添加 ExecStartPost=/bin/sleep 0.1 Can't open PID file /var/run/keepalived.pid (yet?) after start: No suchfile or directory 使用 systemctl start keepalived 时,先调用的是 keepalived.service,启动时 keealived.pid 文件并未生成 在 /usr/lib/systemd/system/keepalived.service 中 [service] 模块下添加 ExecStartPost=/bin/sleep 0.1
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