nginx开启keep-alive：
upstream prematurely closed connection while reading response header from upstream, client: X.90.10, server: www.example.com, request: "POST /web/?a=b HTTP/1.1", upstream: "http://X.32.238:80/web/?a=b", host: "www.example.com"
解决：https://blog.csdn.net/doctor_who2004/article/details/82806852
