在 Nginx 做反向代理的时候,我们一般会配置 proxy_next_upstream,如果某个 upstream 超时或出错,自动切换到下一个 upstram。

upstream backend{
  server 192.168.0.1;
  server 192.168.0.2;
}
location /example/ {
   proxy_pass http://backend;

   proxy_next_upstream error timeout http_500 non_idemponent;
}

这里有一个地方需要注意,non_idemponent,Nginx 默认对 non-idempotent 请求,比如 POST/LOCK/PATCH,是不进行重试。常见的情况就是 POST 请求出错后不会重试,需要加上该设置。

normally, requests with a non-idempotent method (POST, LOCK, PATCH) are not passed to the next server if a request has been sent to an upstream server (1.9.13); enabling this option explicitly allows retrying such requests;