Method what_is_document_freshness

src/proxy/http/HttpTransact.cc:7284–7471

///////////////////////////////////////////////////////////////////////// This function takes the request and response headers for a cached object, and the current HTTP parameters, and decides if the object is still "fresh enough" to serve. One of the following values is returned: FRESHNESS_FRESH Fresh enough, serve it FRESHNESS_WARNING Stale but client says it's okay FRE

//
//////////////////////////////////////////////////////////////////////////////
HttpTransact::Freshness_t
HttpTransact::what_is_document_freshness(State *s, HTTPHdr *client_request, HTTPHdr *cached_obj_response)
{
  bool       heuristic, do_revalidate = false;
  int        age_limit;
  int        fresh_limit;
  ink_time_t current_age, response_date;
  uint32_t   cc_mask, cooked_cc_mask;
  uint32_t   os_specifies_revalidate;

  if (s->cache_open_write_fail_action & CACHE_WL_FAIL_ACTION_STALE_ON_REVALIDATE) {
    if (is_stale_cache_response_returnable(s)) {
      TxnDbg(dbg_ctl_http_match, "cache_serve_stale_on_write_lock_fail, return FRESH");
      return (FRESHNESS_FRESH);
    }
  }

  //////////////////////////////////////////////////////
  // If config file has a ttl-in-cache field set,     //
  // it has priority over any other http headers and  //
  // other configuration parameters.                  //
  //////////////////////////////////////////////////////
  if (s->cache_control.ttl_in_cache > 0) {
    // what matters if ttl is set is not the age of the document
    // but for how long it has been stored in the cache (resident time)
    int resident_time = s->current.now - s->response_received_time;

    TxnDbg(dbg_ctl_http_match, "ttl-in-cache = %d, resident time = %d", s->cache_control.ttl_in_cache, resident_time);
    if (resident_time > s->cache_control.ttl_in_cache) {
      return (FRESHNESS_STALE);
    } else {
      return (FRESHNESS_FRESH);
    }
  }

  cooked_cc_mask          = cached_obj_response->get_cooked_cc_mask();
  os_specifies_revalidate = cooked_cc_mask & (MIME_COOKED_MASK_CC_MUST_REVALIDATE | MIME_COOKED_MASK_CC_PROXY_REVALIDATE);
  cc_mask                 = MIME_COOKED_MASK_CC_NEED_REVALIDATE_ONCE;

  // Check to see if the server forces revalidation

  if ((cooked_cc_mask & cc_mask) && s->cache_control.revalidate_after <= 0) {
    TxnDbg(dbg_ctl_http_match, "document stale due to server must-revalidate");
    return FRESHNESS_STALE;
  }

  response_date = cached_obj_response->get_date();
  fresh_limit   = calculate_document_freshness_limit(s, cached_obj_response, response_date, &heuristic);
  ink_assert(fresh_limit >= 0);

  current_age = HttpTransactCache::calculate_document_age(s->request_sent_time, s->response_received_time, cached_obj_response,
                                                          response_date, s->current.now);

  // First check overflow status
  // Second if current_age is under the max, use the smaller value
  // Finally we take the max of current age or guaranteed max, this ensures it will
  // age out properly, otherwise a doc will never expire if guaranteed < document max-age
  if (current_age < 0) {