Hello!

On Wed, Feb 05, 2014 at 03:48:50PM -0800, Jeroen Ooms wrote:

> After I added some CORS headers to my API, one of the users of my
> nginx-based system complained about occasional errors with:
>
> upstream sent too big header while reading response header from upstream
>
> He also reported to have worked around the issue using:
>
> proxy_buffers 8 512k;
> proxy_buffer_size 2024k;
> proxy_busy_buffers_size 2024k;
> proxy_read_timeout 3000;
>
> However unfortunately I was unable to reproduce this problem myself. I
> also had a hard time figuring out what the exact problem is.
>
> Some questions:
>
> - What exactly does this error mean? Does it mean that response
> contained too many headers? How many is too many?

Response headers should fit into proxy_buffer_size, see
http://nginx.org/r/proxy_buffer_size. If they don't, the error
is reported.

> - Is it wise to increase the buffer sizes as the user reported? What
> would be sensible defaults?

Certainly no. In most cases defaults used (4k on most platforms)
are appropriate. If big cookies are expected to be returned by a
proxied server, something like 32k or 64k will be good enough. If
larger values are needed, it indicate backend problem.

--
Maxim Dounin
http://nginx.org/

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