nginx transparent proxy: how it works? - nginx

Question

I have a transparent proxy server running on port 8008, I want to send some $uri to this proxy. This is what I have in the proxy server:
server
{
listen 8008;
location / {
resolver 8.8.8.8;
proxy_pass http://$http_host$request_uri;
}
access_log /var/log/nginx/proxy_access.log;
}
This actually works - if I put my host:8008 in any of my browser setting, proxy_access.log will show records like:
myb.row.ser.ip - - [12/Feb/2014:20:09:24 -0600] "GET http://col.stb01.s-msn.com/i/4B/7CC71C50462D34411C88C3623A69A.jpg HTTP/1.1" 200 9075 "http://www.msn.com/" "Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; rv:11.0) like Gecko"
Please note the `"GET http://col.stb01..." portion.
Under one of my virtual server, I setup for a location (sample uri: /www.patterns.com/cat/subcat/sample.html):
location ~* (patterns)
{
set $hostx "";
set $addrs "";
if ( $uri ~ "^/(.*?)(/.*)$") {
set $hostx $1; # could be www.patterns.com
set $addrs $2; # could be /cat/subcat/sample.html
}
proxy_pass http://127.0.0.1:8008/http://$hostx$addrs;
proxy_set_header referer "";
}
The above code does send the captured uri to my proxy server, however what the proxy server sees is different, from the proxy_access.log:
127.0.0.1 - - [12/Feb/2014:20:44:28 -0600] "GET /http://www.patterns.com/cat/subcat/sample.html HTTP/1.0" 502 574 "-" "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/32.0.1700.107 Safari/537.36"
Please note the leading slash in: "GET /http://www.patterns.co...", I believe that causes the proxy server to return the 502 code.
Now my question is: in my location, how do I send the correct uri to the proxy server?
Thanks,

Answer 1

you should remove the "/http://" part in your proxy_pass.
Actually, I don't really understand why you need to get $hostx and $addrs, check nginx doc
While passing request nginx replaces URI part which corresponds to location with one indicated in proxy_pass directive. But there are two exceptions from this rule when it is not possible to determine what to replace:
if the location is given by regular expression;
if inside proxied location URI is changed by rewrite directive, and this configuration will be used to process request (break):
location /name/ {
rewrite /name/([^/] +) /users?name=$1 break;
proxy_pass http://127.0.0.1;
}
For these cases of URI it is transferred without the mapping.