Possible to set proxy_pass as a variable derived from the query_string or header param NGINX proxy?-CodePudding

I have a situation where I'd like to proxy_pass to a backend server, with the url for the server being dynamic and derived from either a url param value or from a header param value. Not sure that is even possible, still a bit of a novice with NGINX proxies.

I had thought that $arg_name was the generic way to get the value for a query string parameter in NGINX, so if I have a URL like ....?proxy=/proxy1, then $arg_proxy should have the value of "/proxy1" ?

What I am aiming for is something like this:

set $proxy  "http:/${arg_proxy}:8042";

location /backend/ {

    proxy_pass $proxy;
    rewrite /backend(.*) $1 break;
    proxy_set_header Host $http_host;
    proxy_request_buffering off;
    proxy_max_temp_file_size 0;
    client_max_body_size 0;
}

I tried that, and a few other variations with settting the variable. It doesn't crash the server, but it is also acting like the value for $arg_proxy is blank, even though it is not, or isn't getting read.

invalid URL prefix in "http:/:8042"

It would be nice to alternatively extract the proxy value from a header param, because there are cases where that would also be helfpul.

Addendum:

I tried something like this using a Cookie:

map $cookie_TEST $proxy_url {

volatile;
default     "";
"pacs-1"    "pacs-1";
"pacs-2"    "pacs-2";
"pacs-3"    "pacs-3";
}

upstream pacs-1 {

server pacs-1:8042;
keepalive 32;
keepalive_requests 1024;
keepalive_time 1h;
keepalive_timeout 600s;
}

upstream pacs-2 {

server pacs-2:8042;
keepalive 32;
keepalive_requests 1024;
keepalive_time 1h;
keepalive_timeout 600s;
}

upstream pacs-3 {

server pacs-3:8042;
keepalive 32;
keepalive_requests 1024;
keepalive_time 1h;
keepalive_timeout 600s;
}

But then in the proxy block:

    if ($proxy_url = 'pacs-1') {
        rewrite /orthanc(.*) $1 break;
        proxy_pass http://pacs-1;
    }
    if ($proxy_url = 'pacs-2') {
        rewrite /orthanc(.*) $1 break;
        proxy_pass http://pacs-2;
    }
    
    if ($proxy_url = 'pacs-3') {
        rewrite /orthanc(.*) $1 break;
        proxy_pass http://pacs-3;
    }

Seems like there should be a way without using if's, which is a bad idea really, but it seems to "work" so far with what I am trying.

CodePudding user response：

Args are uri specific , try using the below example:

location /search {
    set $proxxy "www.google.com";
    if ($args) {
        set $proxxy $arg_proxy;
    }
    if ($proxxy){
        proxy_pass https://$proxxy;
    }
    proxy_pass https://www.google.com;
}

one can't access access args independent of the request.