Method dequeue

src/proxy/http/PreWarmManager.cc:775–813

Use open_list as FILO to adjust size of list. ( A new sm is pushed in front of the list by PreWarmQeueu::push() ) When the list has redundant sm(s), they will be closed by inactivity timeout. */

   When the list has redundant sm(s), they will be closed by inactivity timeout.
 */
PreWarmSM *
PreWarmQueue::dequeue(const PreWarm::SPtrConstDst &target)
{
  PreWarmSM *sm = nullptr;

  auto res = _map.find(target);
  if (res == _map.end()) {
    // no such pool
    return nullptr;
  }

  const PreWarm::SPtrConstDst &dst  = res->first;
  Info                        &info = res->second;

  Queue *q = info.open_list;
  while (!q->empty()) {
    sm = q->front();
    q->pop_front();

    if (sm->handler == &PreWarmSM::state_open) {
      _cop_list.remove(sm);
      break;
    }

    _delete_prewarm_sm(sm);
    sm = nullptr;
  }

  // stat
  if (sm == nullptr) {
    ++info.stat.miss;
  } else {
    ++info.stat.hit;
  }

  _prewarm_on_dequeue(dst, info);

  return sm;
}

void
PreWarmQueue::_new_prewarm_sm(const PreWarm::SPtrConstDst &dst, const PreWarm::SPtrConstConf &conf,