错误信息：upstream prematurely closed connection while reading response header from upstream,
Symptom: nginx normally receives the request, normal call back interfaces, the interface returns to normal obtain information, but the request has been interrupted
solution:
location / {
proxy_http_version 1.1;
proxy_set_header Connection "Keep-Alive";
}
the reason:
nginx defaults http1.0 get a response returned from the back end to the client, but does not support HTTP1.0 keepalive;
Default proxy_set_header Connection close: close the connection to the backend server is active, this will cause a client requests any have had a TIME-WAIT state on the backend server connection