id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	uname	nginx_version
2222	add_after_body concatenates (upstream proxied) gziped content with uncompressed local data	dwt@…		"I've now spent several days debugging to find out that using Nginx's `add_after_body` directive, Nginx doesn't decompress and recompress upstream proxied responses when appending the results of the sub request (which yealds uncompressed data).

I'd like to think that this should either produce a warning (as clients tend to discard the uncompressed data appended to the compressed data) or should transparently (maybe optionally) decompress, append and then recompress the http stream to produce output that is actually understandable by clients.

It may also be possible to compress the response from `add_after_body` and concatenate the compressed response to the compressed upstream servers response (not quite sure about my understanding of gzip here).

In any way, I'd like to suggest to either emit a warning (none was given, even with `error_log ... debug;`) or form correct (as in readable by clients) responses.

Some excerpts from my config:

{{{
include conf.d/error_logging.include;
include conf.d/workers.include;

http {
    # Disabling both gzip and enabling gunzip works around the problem that nginx tries to concatenate 
    # the add_after_body content to gziped upstream responses, which leads to the appended uncompressed
    # content being ignored/discarded by the client.
    # gzip off;
    # gunzip on;
    
    include conf.d/access_logging.include;
    include conf.d/mime_types.include;

    server {
        listen 8000;
        server_name localhost;

        location /proxy_static {
            # returns uncompressed responses
            alias /srv/www/static;
            add_after_body """"; # disable add after body to these locations
        }
        add_after_body /proxy_static/custom_css_and_js.html;
        
        location / {
            # returns gzip compressed responses
            proxy_pass http://host.docker.internal:8001;
        }
    }
    
}
}}}"	enhancement	new	minor		nginx-module	1.19.x				Linux 61c804a37588 5.10.25-linuxkit #1 SMP Tue Mar 23 09:27:39 UTC 2021 x86_64 GNU/Linux	nginx version: nginx/1.19.7