The relationship between directive "scgi_busy_buffers_size" and other two directives is not recorded clearly.

[zhoushulin1992@…]

In the document of directive "scgi_busy_buffers_size", it says that "By default, size is limited by the size of two buffers set by the scgi_buffer_size and scgi_buffers directives". Indeed, based on the handling logic in src/http/modules/ngx_http_scgi_module.c, the value of "scgi_busy_buffers_size" must be equal or greater than the maximum of the value of "scgi_buffer_size" and "scgi_buffers" size. So it is recommended to add this information in the doc of "scgi_busy_buffers_size"(​https://nginx.org/en/docs/http/ngx_http_scgi_module.html#scgi_busy_buffers_size).

The same situation happens in directive "scgi_temp_file_write_size" in ​https://nginx.org/en/docs/http/ngx_http_scgi_module.html#scgi_temp_file_write_size, and directive "scgi_max_temp_file_size" in ​https://nginx.org/en/docs/http/ngx_http_scgi_module.html#scgi_max_temp_file_size. They should all be equal or greater than the maximum of the value of "scgi_buffer_size" and "scgi_buffers" size.

What's more, the value of directive "scgi_busy_buffers_size" must be less than (number-of-scgi_buffers - 1)*size-of-scgi_buffers. This also should be recorded.

[Maxim Dounin]

Closing this as duplicate of #2086, which is more generic, as applies to proxy.