Abstract behavior of nginx

Hi,

I can’t understand behavior of nginx.
Version 1.2.1 on Debian Wheezy from official repository. I send requests
to cdn.some_domain.pl server, and in log
/var/log/nginx/cdn.some_domain.pl/test.log I see:

image/gif:1
image/png:1
image/png:1
image/gif:1
image/png:1
image/gif:1

It is correct. If I remove hash sign in 3 last line of configuration
file, nginx puts to /var/log/nginx/cdn.some_domain.pl/test.log below
entries:

-:0
-:0
-:0
-:0
-:0
-:0

I don’t understand, why in this configuration, value of
$sent_http_content_type variable is empty.

Configuration:

user www-data;
worker_processes 4;
pid /var/run/nginx.pid;
events {
worker_connections 768;
}
http {
sendfile on;
tcp_nopush on;
tcp_nodelay on;
keepalive_timeout 65;
types_hash_max_size 2048;
server_tokens off;
include /etc/nginx/mime.types;
default_type application/octet-stream;
access_log /var/log/nginx/access.log;
error_log /var/log/nginx/error.log;
gzip on;
gzip_disable “msie6”;
proxy_set_header Host $host;
proxy_set_header X-Forwarded-Host $host;
proxy_set_header X-Forwarded-Server $host;

            map $sent_http_content_type $cdn {
                           default         0;
                           text/css        1;
                           text/javascript 1;
                           image/x-icon    1;
                           image/gif       1;
                           image/jpeg      1;
                           image/png       1;
            }

            log_format test $sent_http_content_type:$cdn;

server {
listen 82 default; ## listen for ipv4
listen [::]:82 default ipv6only=on; ## listen for ipv6
server_name localhost “”;
access_log /var/log/nginx/localhost.access.log;
error_log /var/log/nginx/localhost.error.log;
location / {
root /var/www;
index index.html index.htm;
}
location /test.txt {
proxy_pass http://$server_addr:8080;
}
}

server {
listen 82;
server_name cdn.some_domain.pl;
location / {
proxy_pass http://$server_addr:8080;
}
location /test.jsp {
proxy_pass http://$server_addr:8080;
allow 10.0.0.0/8;
deny all;
}
access_log /var/log/nginx/cdn.some_domain.pl/test.log
test;

if ($cdn) {

return 404;

}

}
}

Regards,
Jarek

Hello,

It makes sense… Thank you for your help.

Regards,
Jarek

Hello!

On Fri, Nov 22, 2013 at 02:47:23PM +0100, Pomorski Jarosław wrote:

image/gif:1
-:0
-:0
-:0

I don’t understand, why in this configuration, value of
$sent_http_content_type variable is empty.

[…]

            map $sent_http_content_type $cdn {
                           default         0;
                           text/css        1;
                           text/javascript 1;
                           image/x-icon    1;
                           image/gif       1;
                           image/jpeg      1;
                           image/png       1;
            }

[…]

if ($cdn) {

return 404;

}

The “if ($cdn)” is evaluated while processing rewrite rules, and
at this point value of $sent_http_content_type isn’t yet known
(because response isn’t sent). But due to this evaluation
calculated values of the $sent_http_content_type and $cdn
variables are cached, and not re-evaluated again later.

That is, what you see in logs is a value of the
$sent_http_content_type variable at the time the variable was
evaluated for the first time during request processing.


Maxim D.
http://nginx.org/en/donation.html

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