Method OnDetectSlowConnecting

library/cpp/neh/http2.cpp:1175–1210

it seems we have lost TCP SYN packet, create extra connection for decrease response time

    //it seems we have lost TCP SYN packet, create extra connection for decrease response time
    void THttpRequest::OnDetectSlowConnecting() {
#ifdef DEBUG_STAT
        ++TDebugStat::ConnSlow;
#endif
        //use some io_service (Run() thread-executor), from first conn. for more thread safety
        THttpConnRef conn = GetConn();

        if (!conn) {
            return;
        }

        THttpConnRef conn2;
        try {
            conn2 = THttpConn::Create(conn->GetIOService());
        } catch (...) {
            return; // cant create spare connection, simple continue use only main
        }

        {
            TGuard<TSpinLock> g(SL_);
            Conn2_ = conn2;
        }

        if (Y_UNLIKELY(Canceled_)) {
            ReleaseConn2();
        } else {
            //use connect timeout for disable detecting slow connecting on second conn.
            TEndpoint ep(new NAddr::TAddrInfo(&*Addr_->Addr.Begin()));
            try {
                conn2->StartRequest(WeakThis_, ep, Addr_->Id, THttp2Options::ConnectTimeout);
            } catch (...) {
                // ignore errors on spare connection
                ReleaseConn2();
            }
        }
    }

    void THttpRequest::OnConnect(THttpConn* c) {
        THttpConnRef extraConn;