Method build_response_from_cache

src/proxy/http/HttpTransact.cc:3001–3123

////////////////////////////////////////////////////////////////////////// Name : build_response_from_cache() Description: build a client response from cached response and client request Input : State, warning code to be inserted into the response header Output : Details : This function is called if we decided to serve a client request using a cached response. It is called by h

//
///////////////////////////////////////////////////////////////////////////////
void
HttpTransact::build_response_from_cache(State *s, HTTPWarningCode warning_code)
{
  HTTPHdr       *client_request  = &s->hdr_info.client_request;
  HTTPHdr       *cached_response = nullptr;
  HTTPHdr       *to_warn         = &s->hdr_info.client_response;
  CacheHTTPInfo *obj;

  if (s->api_update_cached_object == HttpTransact::UPDATE_CACHED_OBJECT_CONTINUE) {
    obj = &s->cache_info.object_store;
    ink_assert(obj->valid());
  } else {
    obj = s->cache_info.object_read;
  }
  cached_response = obj->response_get();

  // If the client request is conditional, and the cached copy meets
  // the conditions, do not need to send back the full document,
  // just a NOT_MODIFIED response.
  // If the request is not conditional,
  // the function match_response_to_request_conditionals() returns
  // the code of the cached response, which means that we should send
  // back the full document.
  HTTPStatus client_response_code =
    HttpTransactCache::match_response_to_request_conditionals(client_request, cached_response, s->response_received_time);

  switch (client_response_code) {
  case HTTP_STATUS_NOT_MODIFIED:
    // A IMS or INM GET client request with conditions being met
    // by the cached response.  Send back a NOT MODIFIED response.
    TxnDbg(dbg_ctl_http_trans, "Not modified");
    SET_VIA_STRING(VIA_DETAIL_CACHE_LOOKUP, VIA_DETAIL_HIT_CONDITIONAL);

    build_response(s, cached_response, &s->hdr_info.client_response, s->client_info.http_version, client_response_code);
    s->cache_info.action = CACHE_DO_NO_ACTION;
    s->next_action       = SM_ACTION_INTERNAL_CACHE_NOOP;
    break;

  case HTTP_STATUS_PRECONDITION_FAILED:
    // A conditional request with conditions not being met by the cached
    // response.  Send back a PRECONDITION FAILED response.
    TxnDbg(dbg_ctl_http_trans, "Precondition Failed");
    SET_VIA_STRING(VIA_DETAIL_CACHE_LOOKUP, VIA_DETAIL_MISS_CONDITIONAL);

    build_response(s, &s->hdr_info.client_response, s->client_info.http_version, client_response_code);
    s->cache_info.action = CACHE_DO_NO_ACTION;
    s->next_action       = SM_ACTION_INTERNAL_CACHE_NOOP;
    break;

  // Check if cached response supports Range. If it does, append
  // Range transformation plugin
  // A little misnomer. HTTP_STATUS_RANGE_NOT_SATISFIABLE
  // actually means If-Range match fails here.
  // fall through
  default:
    SET_VIA_STRING(VIA_DETAIL_CACHE_LOOKUP, VIA_DETAIL_HIT_SERVED);
    if (s->method == HTTP_WKSIDX_GET || (s->txn_conf->cache_post_method == 1 && s->method == HTTP_WKSIDX_POST) ||
        s->api_resp_cacheable == true) {