这里分享一个关于 nginx client_body_buffer_size 参数的解决案例。
描述：前端同事反馈，在发POST 请求带参数的时候，过Nginx 会报错；但是单台测试tomcat，POST 很正常；看了下请求参数，好大一堆，的确比较多，问题应该在nginx上，于是查看nginx 报错日志，进行分析
现象：用Postman 测试发送请求，POST报错不成功，参数好大一堆。
查看nginx error 日志分析：
2016/09/13 12:40:59 [warn] 15598#0: *35462539 an upstream response is buffered to a temporary file /usr/local/nginx/proxy_temp/9/66/0001124669 while reading upstream, client: 116.226.84.138, server:*****.juxinli.com, request: "POST /devPlatformApi/rest/fengkong/variate_dir HTTP/1.1", upstream: "http://******/devPlatformApi/rest/fengkong/variate_dir", host: "***.***.com"
分析解决：从官方给出的定义，是client_body_buffer_size 参数定义过小而发送请求超过默认参数16K大小了。
| Syntax: | client_body_buffer_size |
|---|---|
| Default: |
client_body_buffer_size 8k|16k; |
| Context: | http, server, location |
Sets buffer size for reading client request body. In case the request body is larger than the buffer, the whole body or only its part is written to a temporary file. By default, buffer size is equal to two memory pages. This is 8K on x86, other 32-bit platforms, and x86-64. It is usually 16K on other 64-bit platforms.
官方文档：
http://nginx.org/en/docs/http/ngx_http_core_module.html#client_body_buffer_size
解决办法：client_body_buffer_size 1024k; 加大到1024K,因为默认16K 太小，请求参数过多时，会出现此类报错。
问题解除，恢复正常：
官方文档：
http://nginx.org/en/docs/http/ngx_http_core_module.html#client_body_buffer_size
其他帖子：
https://my.oschina.net/linland/blog/373315?p=1
可以研读下，弄清楚该配置参数及解决方法。