How do we configure symfony 1.4 to use it with Varnish?

I finally found on my own how to resolve my problem, so I'm going to share how I did it :

To start, you should know that symfony creates automatically a PHP session every time a page is called. So, what I did was to deactivate that default behaviour. To do so, I added on the factories.yml a storage factory (the default one : sfSessionStorage) with the auto_start parameter set to false:

storage:  class: sfSessionStorage  param:    auto_start: false

Then, I created a filter to handle the http headers :

I firstly added it to the filters.yml file

http_header:  class: myHttpHeaderFilter

And then I added a myHttpHeaderFilter.php class on the lib folder, where I handled all the headers I wanted. For example :

class myHttpHeaderFilter extends sfFilter{    public function execute($filterChain)    {      //execute the next filter in the chain      $filterChain->execute();      //code after here runs after action      // Filters don't have direct access to the request and user objects.      // You will need to use the context object to get them      $request = $this->getContext()->getRequest();      $path = $request->getPathInfo();      if (substr($path, 0, 5) == "/foo") // We cache only some of the /foo requests      {          if (strstr($path, "bar")) // We cache the request containing bar during half an hour hour              $this->getContext()->getResponse()->addCacheControlHttpHeader('max-age=1800');          else // All the other requests are cached during 24 hours          {              $this->getContext()->getResponse()->addCacheControlHttpHeader('max-age=86400');          }      }      else // The other requests are not cached          $this->getContext()->getResponse()->addCacheControlHttpHeader('no-cache, no-store');    }}

And that was it !

I also modified the vcl_recv on the server side, to ensure that all requests that not need to be cached are not (in theory, it is not mandatory to do so, because I handled it on symfony, it is just a "double-check").

sub vcl_recv {     if (req.http.Authorization || req.http.Cookie) {         /* Not cacheable by default */         return (pass);     }     if (req.request != "GET" && req.request != "HEAD") {         /* We only deal with GET and HEAD by default */         return (pass);     }     if (req.url ~ "/user") /* Requests containing user data are never cached */        {                return (pass);        }     return (lookup);}