Method is_request_cache_lookupable

src/proxy/http/HttpTransact.cc:6073–6132

////////////////////////////////////////////////////////////////////////// Name : is_request_cache_lookupable() Description: check if a request should be looked up in cache Input : State, request header Output : true or false Details : //////////////////////////////////////////////////////////////////////////

//
///////////////////////////////////////////////////////////////////////////////
bool
HttpTransact::is_request_cache_lookupable(State *s)
{
  // ummm, someone has already decided that proxy should tunnel
  if (s->current.mode == TUNNELLING_PROXY) {
    return false;
  }
  // don't bother with remaining checks if we already did a cache lookup
  if (s->cache_info.lookup_count > 0) {
    return true;
  }
  // is cache turned on?
  if (!s->txn_conf->cache_http) {
    SET_VIA_STRING(VIA_DETAIL_TUNNEL, VIA_DETAIL_TUNNEL_CACHE_OFF);
    return false;
  }
  // GET, HEAD, POST, DELETE, and PUT are all cache lookupable
  if (!HttpTransactHeaders::is_method_cache_lookupable(s->method) && s->api_req_cacheable == false) {
    SET_VIA_STRING(VIA_DETAIL_TUNNEL, VIA_DETAIL_TUNNEL_METHOD);
    return false;
  }
  // don't cache page if URL "looks dynamic" and this filter is enabled
  // We can do the check in is_response_cacheable() or here.
  // It may be more efficient if we are not going to cache dynamic looking urls
  // (the default config?) since we don't even need to do cache lookup.
  // So for the time being, it'll be left here.

  // If url looks dynamic but a ttl is set, request is cache lookupable
  if ((!s->txn_conf->cache_urls_that_look_dynamic) && url_looks_dynamic(s->hdr_info.client_request.url_get()) &&
      (s->cache_control.ttl_in_cache <= 0)) {
    // We do not want to forward the request for a dynamic URL onto the
    // origin server if the value of the Max-Forwards header is zero.
    int max_forwards = -1;
    if (s->hdr_info.client_request.presence(MIME_PRESENCE_MAX_FORWARDS)) {
      MIMEField *max_forwards_f = s->hdr_info.client_request.field_find(MIME_FIELD_MAX_FORWARDS, MIME_LEN_MAX_FORWARDS);

      if (max_forwards_f) {
        max_forwards = max_forwards_f->value_get_int();
      }
    }

    if (max_forwards != 0) {
      SET_VIA_STRING(VIA_DETAIL_TUNNEL, VIA_DETAIL_TUNNEL_URL);
      return false;
    }
  }

  // Don't look in cache if it's a RANGE request but the cache is not enabled for RANGE.
  if (!s->txn_conf->cache_range_lookup && s->hdr_info.client_request.presence(MIME_PRESENCE_RANGE)) {
    SET_VIA_STRING(VIA_DETAIL_TUNNEL, VIA_DETAIL_TUNNEL_HEADER_FIELD);
    return false;
  }

  // Even with "no-cache" directive, we want to do a cache lookup
  // because we need to update our cached copy.
  // Client request "no-cache" directive is handle elsewhere:
  // update_cache_control_information_from_config()