why nginx is not compressing reply from proxied server?

[Maxim Dounin]

Hello!

On Tue, May 11, 2021 at 06:16:46PM +0300, Peter Volkov wrote:

> Err, After few hours of debugging, and writing email here, I've realised
> that I have `gzip off;` in http {} block of configuration. After enabling
> gzip in http block everything works fine. Is it correct behaviour that no
> warning is issued with such configuration?

The configuration specified in http{} block applies, unless you've 
redefined the configuration in more specific scope, such as 
server{} or location{}.  That is, the following configuration 
won't use gzip:

    http {
        gzip off;

        server {
            listen 80;
        }
    }

But the following will:

    http {
        gzip off;

        server {
            listen 80;
            gzip on;
        }
    }

That's how it is expected to work.

If a configuration with "gzip off;" at the http level and "gzip on;" 
at the server level doesn't work for you, but changing it to "gzip 
on;" at the http level works, most likely this means that you are 
looking at the wrong server{} block.

Note that the configuration you've provided listens on the port 80 
(the default):

> > server {
> >     gzip on;
> >     gzip_comp_level 5;
> >     gzip_http_version 1.0;
> >     gzip_buffers 4 32k;
> >     gzip_min_length 0;
> >     gzip_types application/octet-stream;
> >     gzip_proxied any;
> >     gzip_vary on;
> >
> >     proxy_buffering off;
> >
> >     location / {
> >         proxy_pass http://10.239.254.17:9102;
> >     }
> > }

And you are testing port 9102, not 80:

> > curl -v IP:9202 -H 'Accept-Encoding: deflate, gzip' -o output

Most likely this means that you are testing against the wrong 
server{} block, and that's why "gzip on;" at http{} level works 
for you.

-- 
Maxim Dounin
http://mdounin.ru/