最近遇到了客户在从我们的服务器下载文件失败时的情况。然后把解决方案一并整理一下以备后续。需要说明的是，我们前端都是使用nginx来做反向代理，后面的逻辑处理采用php的方式。
1、缓存目录不可写
nginx在做反向代理，代理后端的nginx+php-fpm时，在客户端下载文件时，总是下载到一定的大小，就下载不动，查看后端服务器，表现正常，在绕过前端反向代理，直接从后端下载，也正常。检查反向代理服务器日志，抛出如下异常：
2017/01/16 11:54:38 [warn] 3748#0: *61038342 an upstream response is buffered to a temporary file /usr/local/tengine/proxy_temp/5/03/0000000035 while reading upstream, client: 192.168.42.190, server: preview-qa.fdccloud.com, request: "GET /zip/033ca15a28b33298b46bc1e7eb2ea0f24cde16f9/%E9%99%84%E4%BB%B6%E9%97%AE%E9%A2%98/04%E6%98%8E%E6%BA%90%E7%A7%BB%E5%8A%A8V3.0%E4%BA%A7%E5%93%81%E5%8F%91%E5%B8%83%E5%85%AC%E5%91%8A-%E7%A7%BB%E5%8A%A8%E8%AE%A1%E5%88%92.pptx HTTP/1.1", upstream: "http://127.0.0.1:2016/zip/033ca15a28b33298b46bc1e7eb2ea0f24cde16f9/%E9%99%84%E4%BB%B6%E9%97%AE%E9%A2%98/04%E6%98%8E%E6%BA%90%E7%A7%BB%E5%8A%A8V3.0%E4%BA%A7%E5%93%81%E5%8F%91%E5%B8%83%E5%85%AC%E5%91%8A-%E7%A7%BB%E5%8A%A8%E8%AE%A1%E5%88%92.pptx", host: "preview-qa.fdccloud.com"
proxy_buffer_size 512k; proxy_buffers 4 512k; proxy_busy_buffers_size 512k; proxy_temp_file_write_size 512k;
2016/11/25 11:23:47 [error] 67663#0: *11 upstream prematurely closed connection while reading upstream, client: ...
被代理服务器的错误日志：
2016/11/24 23:33:02 [error] 5833#101125: *8559 upstream timed out (60: Operation timed out) while reading response header from upstream, client: ....
proxy_pass http://192.168.0.1; proxy_redirect default; proxy_buffering off;
proxy_send_timeout 90; #后端服务器数据回传时间(代理发送超时) proxy_read_timeout 90; #连接成功后，后端服务器响应时间(代理接收超时)
原文：http://www.cnblogs.com/breezey/p/6740229.html