varnish or squid reverse proxy behind corp proxy

Question

How to configure varnish(or if someone can hint me to squid im fine) to cache requests from backend, but connect to backend through http_proxy

So I try to:

backend default {
    .host = "10.1.1.1";
    .port = "8080";
}

backend corp_proxy {
  .host = "proxy";
  .port = "8080";
}
sub vcl_recv {
    # Happens before we check if we have this in cache already.
    #
    # Typically you clean up the request here, removing cookies you don't need,
    # rewriting the request, etc.
    set req.backend_hint = corp_proxy;
    set req.url ="http://" + req.http.host + req.url;
}

This is the right way I think, can you tell me what's the problem? — Dat Tran, Aug 16 '18 at 01:37

score 2 · Answer 1 · answered Dec 15 '20 at 12:59

Varnish (or other web caching proxies) caches a request, based on its cache-related headers (like Cache-Control).
Unfortunately, many web applications don't set these headers correctly. So we should use a more aggressive approach to cache some well-known items, e.g., pictures, .js or .css files.

Moreover, this line set req.url ="http://" + req.http.host + req.url; is not required, because Varnish sends the request, as is, to your designated backend.

Here is my recommended config:

backend corp_proxy {
  .host = "proxy";
  .port = "8080";
}

sub vcl_recv {
  
  // Determine backend
  if ( req.http.host ~ ".example.com" ) {
    set req.backend_hint = corp_proxy;
    
    // Determine cacheable items
    if( req.url ~ "\.(css|js|jpg|jpeg|png|gif|ico) {
      unset req.http.Cookie;
      unset req.http.Cache-Control;
    }
  }
  
}

sub vcl_backend_response {
  
  if( bereq.http.host ~ ".example.com" ) {
    if (bereq.url ~ "\.(css|jsjpg|jpeg|png|gif|ico)") {
      set beresp.ttl = 20m; // I opt for 20 minutes of caching by your mileage may vary
  }

}

varnish or squid reverse proxy behind corp proxy

1 Answers1