upstream timed out (110: Connection timed out) while reading response header from upstream
Nginx代理配置如下：
###proxy settings start
proxy_http_version 1.1;
proxy_connect_timeout 3s;
proxy_read_timeout 3s;
proxy_send_timeout 3s;
proxy_buffer_size 128k;
proxy_buffers 256 16k;
proxy_busy_buffers_size 128k;
proxy_ignore_client_abort on;
###proxy settings end语法：proxy_read_timeout time;
默认值：proxy_read_timeout 60s;
上下文：http，server，location
Defines a timeout for reading a response from the proxied server. The timeout is set only between two successive read operations, not for the transmission of the whole response. If the proxied server does not transmit anything within this time, the connection is closed.
需要注意的是，这个超时时间并不是针对单个请求的响应超时时间，而是针对两个成功响应之间的间隙，即如果被代理服务器在设置时间内没有发送任何数据，连接将被关闭
proxy_http_version设置为1.1，Nginx和被代理服务器之间默认使用长连接进行通信
在req2的响应返回之前，距resp1成功返回的时间已经超过了proxy_read_timeout的设置值（proxy_read_timeout设置的值比较小，并且系统QPS较低），Nginx直接断开了连接导致无法成功获取req2的响应
修改nginx配置，将proxy_read_timeout的值由3s修改为10s
- upstream timed Connection out responseupstream timed connection out upstream_response_time upstream_response_time time request_time response err_connection_timed_out err_connection_timed_out connection浏览器 server received response upstream connection actively upstream错误 time-out timed-out operation-timed-out-carlzeng