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

[zhoushulin1992@…]

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

The same situation happens in directive "proxy_temp_file_write_size" in ​https://nginx.org/en/docs/http/ngx_http_proxy_module.html#proxy_temp_file_write_size, and directive "proxy_max_temp_file_size" in ​https://nginx.org/en/docs/http/ngx_http_proxy_module.html#proxy_max_temp_file_size. They should all be equal or greater than the maximum of the value of "proxy_buffer_size" and "proxy_buffers" size.

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

[Maxim Dounin]

See also #2085, #2087, and #2088.

[Maxim Dounin]

Thank you for your suggestion. It is believed that not all limitations have to be documented, mostly because this needlessly complicates reading of the documentation, and appropriate error reported during configuration parsing is enough.