sueboy: failover

frontent ft_app bind 10.0.0.1:80 default_backend bk_app_main backend bk_app_main server s1 10.0.0.101:80 check server s2 10.0.0.102:80 check server s3 10.0.0.103:80 check backup server s4 10.0.0.104:80 check backup

frontent ft_app bind 10.0.0.1:80 default_backend bk_app_main backend bk_app_main option allbackups server s1 10.0.0.101:80 check server s2 10.0.0.102:80 check server s3 10.0.0.103:80 check backup server s4 10.0.0.104:80 check backup

https://serverfault.com/questions/480241/nginx-failover-without-load-balancing


pstream backend {
    server 1.2.3.4:80 fail_timeout=5s max_fails=3;
    server 4.5.6.7:80 backup;
}

server {
    listen 80;
    server_name whatevs.com;

    location / {
        proxy_pass http://backend;
    }
}

https://www.cnblogs.com/biglittleant/p/8979887.html

backup 预留的备份服务器，当其他所有的非backup服务器出现故障或者忙的时候，才会请求backup机器，因为这台集群的压力最小。

max_fails 允许请求失败的次数，默认是1，当超过最大次数时，返回proxy_next_upstream模块定义的错误。0表示禁止失败尝试，企业场景：2-3.京东1次，蓝汛10次，根据业务需求去配置。

fail_timeout，在经历了max_fails次失败后，暂停服务的时间。京东是3s，蓝汛是3s，根据业务需求配置。常规业务2-3秒合理。

例：如果max_fails是5，他就检测5次，如果五次都是502.那么，他就会根据fail_timeout 的值，等待10秒，再去检测。

https://blog.51cto.com/wangwei007/1103727

sueboy

EExcel 丞燕快速查詢2

haproxy failover backup server

Normal backup servers： In this case, s3 will be used first, until it fails, then s4 will be used.

Multiple backup servers： In this case, both s3 and s4 will be used if they are available.

option allbackups

nginx failover without load balancing