[Qt-interest] wget vs. QHttp download

[Christian Dähn]

Hi,

be careful using the QNAM - it's only working asynchronously and needs
an event queue - which can lead to very big problems and slow downs
(my experience runs from industrial apps build on Qt 2.x up to 4.6).

Here an example for a simple http download:

   QString m_Hostname = "example.com";
    QNetworkAccessManager manager(this);
    QNetworkReply *reply = manager.get(QNetworkRequest(QUrl("http://" + m_HostName)));
    if (!reply)
        throw runtime_error("start(): invalid network reply pointer!");

    // wait for finished network reply
    QEventLoop loop;
    QTimer timer;
    QObject::connect(reply,  SIGNAL(finished()), &loop, SLOT(quit()));
    QObject::connect(&timer, SIGNAL(timeout()), &loop, SLOT(quit()));
    timer.start(THREAD_WAIT_TIME);
    loop.exec();

    QString html = reply->readAll();

    if (reply->error() != QNetworkReply::NoError || html.length() < 1) {
        qWarning("cannot connect to %s!", qPrintable(m_HostName));
    }


I personally dislike the massive use and new dependencies to the main event loop -
till now I found no way to use QNAM in a blocking way - like the waitForXxx() calls of
QIODevice or QAbstractSocket.

@Trolls:
The new QNAM is a cool solutions if I only care about smart API design -
but in daily life it hast some serious pitfalls - like the performance problems
caused by many QNAM actions running in massive multithreading apps.

Did you ever thought about using QNAM in massive multithreading environments?
Flooding the main eventloop causes my apps to slow down - so I have to use
non-Qt classes - or to write my own QNAM implementation using the QAbstractSockets.

ciao,
Chris
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