Too many "HTTP 400 – Bad Request"

MonoSlon

Hello,

Our team is developing application using Qt 4.8.2. This application periodically makes many http and https requests to our servers and we found that there are a lots of "400" status codes in the log-files of our web servers (nginx). There are much more such bad requests than "good" requests.

We've found that our app often opens "empty" connection, i mean that it establishes tcp connection with web server and do not send anything to this socket.

Is it a bug or is it a normal behavior and how can it be handled?

MonoSlon

here is a code of test app that reproduce this issue.

file main.cpp:
[code]
#include <QCoreApplication>
#include <QTimer>
#include <Sample.h>
#include <Windows.h>

int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);

Sample obj;

// QTimer::singleShot(10000, &obj, SLOT(onTimer()));

for (int i = 0; i < 3; i++) {
    obj.makeRequest();
}

while(true) {
    Sleep(1000);
    obj.makeRequest();
}

int ret = a.exec&#40;&#41;;
return ret;

}
[/code]

file sample.h
[code]
#ifndef SAMPLE_H
#define SAMPLE_H

#include <QObject>
#include <QList>
#include <QtNetwork/QNetworkAccessManager>
#include <QtNetwork/QNetworkReply>
#include <QtNetwork/QSslError>

class Sample : public QObject
{
Q_OBJECT
public:
explicit Sample(QObject *parent = 0);

void startTest(&#41;;
void makeRequest();

signals:

public slots:
void sslErrors(QNetworkReply *reply, const QList<QSslError> &errors);
void onTimer();
void onRequestFinish();
void onError(QNetworkReply::NetworkError error);

private:
QNetworkAccessManager *_manager;

};

#endif // SAMPLE_H

[/code]

file sample.cpp
[code]
#include <Sample.h>

#include <QCoreApplication>
#include <QDebug>
#include <QUrl>
#include <QtNetwork/QNetworkRequest>

Sample::Sample(QObject parent)
: QObject(parent), _manager(new QNetworkAccessManager(this))
{
connect(this->_manager, SIGNAL(sslErrors(QNetworkReply, const QList<QSslError>&)),
this, SLOT(sslErrors(QNetworkReply *, const QList<QSslError>&)));
}

void Sample::startTest()
{
makeRequest();
}
[code]
void Sample::makeRequest()
{
QUrl request("https://localhost:8443/restapi?method=games.getMaintenance");

QNetworkReply *reply = (1 == 1)
    ? this->_manager->get(QNetworkRequest(request))
    : this->_manager->post(QNetworkRequest(request), request.encodedQuery());

connect(reply, SIGNAL(finished()), this, SLOT(onRequestFinish()));
connect(reply, SIGNAL(error(QNetworkReply::NetworkError)), this, SLOT(onError(QNetworkReply::NetworkError)));

qDebug() << "makeRequest" << request;

}

void Sample::onRequestFinish()
{
qDebug() << "onRequestFinish";

QNetworkReply *reply = qobject_cast<QNetworkReply*>(QObject::sender());
reply->deleteLater();

QString response = QString::fromUtf8(reply->readAll());
QNetworkReply::NetworkError error = reply->error();

qDebug() << response << error;

}

void Sample::onError(QNetworkReply::NetworkError error)
{
qDebug() << "error" << error;
}

void Sample::sslErrors(QNetworkReply *reply, const QList<QSslError> &errors)
{
qDebug() << "sslErrors";
Q_FOREACH(QSslError error, errors) {
qDebug() << error;
}

reply->ignoreSslErrors();

}

void Sample::onTimer()
{
QCoreApplication::quit();
}

[/code]

AcerExtensa

Please use "code" tags around your code to make it readable...

MonoSlon

I'm sorry. Updated.

MonoSlon

Found this:
[url]https://bugreports.qt-project.org/browse/QTBUG-14783?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel[/url]

Is there a way to force desktop application not to open additional parallel channels (tcp connections) if it is not really necessary? Especially for the SSL.

misterion

Up. We have same issue as MonoSlon :(

tzander

I noticed one big problem; you schedule all your requests in main. Before you start the event-loop (the exec line).

Please try to restructure your code to
a) avoid a sleep() call. Really, you can't have Sleep() in your code.
b) make the requests being called be called in the event-loop. I suggest using QTimer::singleShot()

MonoSlon

I tried to change the code this way:
[code]
...
QTimer::singleShot(3000, &obj, SLOT(startTest()));
int ret = a.exec();
...
[/code]
but it didn't make changes.

MonoSlon

Sample::startTest was changed respectively:
[code]
void Sample::startTest()
{
for (int i = 0; i < 3; i++) {
makeRequest();
}
}
[/code]

this opens 6 channels, only 3 are used.

radzaw

We are having the same problem. Manyyy connections without any content to our API server :/