How to disable Nginx double gzip encoding when fastcgi backend occasionally serves gzipped with content-encoding?

Question

Is there any clever way to trick nginx to stop gzip if the backend already has set the "content-encoding" header?

Nginx is configured to gzip the output from the php fastcgi backend.

This works great in 99% of the cases.

Except on rare occasion php will send a raw gzipped file and attach a Content-Encoding: gzip header.

Nginx unfortunately will go right ahead and try to gzip that content a second time.

The produces a double content-encoding: gzip content-encoding: gzip header and double-encoded gzipped body.

Most modern browsers can handle this, Firefox, Chrome.

IE8 cannot, Safari mobile cannot, old Safari 5 for Windows cannot - instead they will show garbled gzipped content because it merges the content-encoding headers and only decodes the gzipped body once.

Thanks for any ideas.

Answer 1

Somewhere in nginx.conf where it applies (there should be a fastcgi_params file somewhere) :

fastcgi_param  HTTP_ACCEPT_ENCODING      "";

This will disable the encoding from the backend.

I hope that still Nginx will serve encoded content after this. (I am not sure)