QThread help please

[munna]

Hi,

I have to call a php file with POST request simultaneoulsy for some n times. For this I am using QThread and QHttp. Here is the code.

The thread part

for(int i = 0;i < noOfThreads; i++)
{
	MyThread *t = new MyThread();
        connect(t, SIGNAL(finished()), t, SLOT(deleteLater()));
	t->run();
}

for(int i = 0;i < noOfThreads; i++)
{
	MyThread *t = new MyThread();
        connect(t, SIGNAL(finished()), t, SLOT(deleteLater()));
	t->run();
}

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The Http Part

op->clearPendingRequests();
for(int i=0;i<n;i++) {
	QString log = GenerateLog();
	QHttpRequestHeader header( "POST", "/somephpfile.php" ) ;
	header.setValue( "Host", ipAddress ) ;
	header.setContentType( "application/x-www-form-urlencoded" ) ;
	http.request(header,QVariant(log).toByteArray());
}

op->clearPendingRequests();
for(int i=0;i<n;i++) {
	QString log = GenerateLog();
	QHttpRequestHeader header( "POST", "/somephpfile.php" ) ;
	header.setValue( "Host", ipAddress ) ;
	header.setContentType( "application/x-www-form-urlencoded" ) ;
	http.request(header,QVariant(log).toByteArray());
}

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The above code is not working. Can someone please help?

Thanks.
Oh by the way here is my run () function

void MyThread::run()
{
	mutex.lock();
	Http list(ipAddress, n);	
	list.SetHost(ipAddress);
	list.info();
	mutex.unlock();	
}

void MyThread::run()
{
	mutex.lock();
	Http list(ipAddress, n);	
	list.SetHost(ipAddress);
	list.info();
	mutex.unlock();	
}

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I am new to both threading and http stuff. It would be great if some one can suggest some tutorial or help.

Thanks a lot.

[wysota]

Where is the mutex defined?

[munna]

mutex is private member variable of the class MyThread

[wysota]

You should call t->start() not t->run().

[munna]

i have tried both, but its not working.

Someone please Help.

Thanks a lot

[wysota]

I'm not sure but maybe QHttp needs an event loop running? What happens if you call exec() at the end of run()?

[munna]

Yes, it works but i have another problem now.

I want to post the request in a loop. For that i wrote

for(int i=0;i<noOfSeconds;i++)
{
	t= QTime::currentTime();
	t.addMSecs(1000);	
 
	for(int j=0;j<logsPerSecond;j++)
	{
		Http list();	
		list.SetHost(ipAddress);
		list.GenerateLog();
                  exec();
 
		t1 = QTime::currentTime();
		if(t1 > t){
			break;
		}
          }
	t1 = QTime::currentTime();
	while(t1 < t){
		t1= QTime::currentTime();
	}
}

for(int i=0;i<noOfSeconds;i++)
{
	t= QTime::currentTime();
	t.addMSecs(1000);	
	
	for(int j=0;j<logsPerSecond;j++)
	{
		Http list();	
		list.SetHost(ipAddress);
		list.GenerateLog();
                  exec();

		t1 = QTime::currentTime();
		if(t1 > t){
			break;
		}
          }
	t1 = QTime::currentTime();
	while(t1 < t){
		t1= QTime::currentTime();
	}
}

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The above code post the request only once, where as it should have posted more than once.

[wysota]

Use a timer and in its timeout slot make a new request.

[munna]

Let me explain it to you in detail.

I have to generate log for n seconds at the rate of m logs per sec. All this should happned in a thread (Let us assume that there are x threads).

Following is my code for it.

x threads are created in a for loop

for(int i = 0; i < x; ++i){
       MyThread *t = new MyThread(ipEdit->text(), serialNo, noOfSecsEdit->value(), noOfSecondEdit->value());
       connect(t, SIGNAL(finished()), t, SLOT(deleteLater()));
       t->start();
}

for(int i = 0; i < x; ++i){
       MyThread *t = new MyThread(ipEdit->text(), serialNo, noOfSecsEdit->value(), noOfSecondEdit->value());
       connect(t, SIGNAL(finished()), t, SLOT(deleteLater()));
       t->start();
}

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The run()

void MyThread::run()
{
	QTime t, t1;	
	for(int i=0;i<noOfSeconds;i++)
	{
		t= QTime::currentTime();
		t.addMSecs(1000);// to know what will be the time after one sec
 
		for(int j=0;j<logsPerSecond;j++)
		{
			Http list();	
			list.SetHost(ipAddress);
			list.GenerateLog();
			exec();
			t1 = QTime::currentTime();
			if(t1 > t){// if one sec is over then come out of the loop
				break;
			}
		}
 
		t1 = QTime::currentTime();
 
		while(t1 < t){//Wait till one sec is finished.
			t1= QTime::currentTime();
		}
	}
}

void MyThread::run()
{
	QTime t, t1;	
	for(int i=0;i<noOfSeconds;i++)
	{
		t= QTime::currentTime();
		t.addMSecs(1000);// to know what will be the time after one sec
	
		for(int j=0;j<logsPerSecond;j++)
		{
			Http list();	
			list.SetHost(ipAddress);
			list.GenerateLog();
			exec();
			t1 = QTime::currentTime();
			if(t1 > t){// if one sec is over then come out of the loop
				break;
			}
		}
		
		t1 = QTime::currentTime();
		
		while(t1 < t){//Wait till one sec is finished.
			t1= QTime::currentTime();
		}
	}
}

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Notice that i am not using mutex any more. With the above code log is generated only once.

Can you tell me why is it generated only once whereas it should have got generated more than once ?

Also can you tell me more about even loop and exec() ?

Thanks a lot.

[jacek]

void MyThread::run()
{
		...
		for(int j=0;j<logsPerSecond;j++)
		{
			Http list();	
			list.SetHost(ipAddress);
			...
			exec();
			...
		}
		...
}

void MyThread::run()
{
		...
		for(int j=0;j<logsPerSecond;j++)
		{
			Http list();	
			list.SetHost(ipAddress);
			...
			exec();
			...
		}
		...
}

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Is this a real code? IMO it shouldn't even compile.

QThread::exec() is a blocking call and returns after you invoke QThread::exit(). Since you don't invoke it anywhere, only a half of the first iteration of the above loop is executed.

Also can you tell me more about even loop and exec() ?

QThread::exec() starts an event loop in the current thread (just like QCoreApplication::exec() or QDialog::exec()). This way QObjects that live in that thread can receive events.

What is that Http class? Does it use QHttp internally? Are you aware that QHttp works asynchronously?

[munna]

Is this a real code? IMO it shouldn't even compile.

Yes this is the real code. I comiples and works, but not as expected.

QThread::exec() is a blocking call and returns after you invoke QThread::exit().

I am new to all this. can you please explain this in more detail or some tutorial.

What is that Http class? Does it use QHttp internally?

Yes, the http class inherits QHttp.

Are you aware that QHttp works asynchronously?

Not before you told. But I do not understand this stuff completely. Can you please explain or refer to some tutorial. I'll be greatful to you.

Thanks a lot. Thanks for your time

[jacek]

Yes this is the real code. I comiples and works, but not as expected.

That's quite interesting. What compiler do you use? Can you compile this program with it?

class Test
{
   public:
      Test() {};
      void foo() {};
};
 
int main()
{
   Test t();
   t.foo();
   return 0;
}

class Test
{
   public:
      Test() {};
      void foo() {};
};

int main()
{
   Test t();
   t.foo();
   return 0;
}

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I am new to all this. can you please explain this in more detail or some tutorial.

Everything you need is in the docs --- just read them carefully. Also check the network/http example.

Your MyThread::run() should look like this:

void MyThread::run()
{
   HttpLogger logger;
   connect( &logger, SIGNAL( finished() ), this, SLOT( quit() ) );
   logger.start();
   exec();
}

void MyThread::run()
{
   HttpLogger logger;
   connect( &logger, SIGNAL( finished() ), this, SLOT( quit() ) );
   logger.start();
   exec();
}

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The rest should be handled by signals & slots of the logger object (or whatever you will call it). HttpLogger::start() should start the timer and after given interval that object should emit finished() signal to stop the thread.

[munna]

can i know what makes you think that this code should not compile ?

I'll look into everything you have suggested and then probably get back.

Thanks a lot.

[jacek]

can i know what makes you think that this code should not compile ?

This:

Http list();

Http list();

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it's a forward declaration of a function, but you use "list" like a variable.

[munna]

oh, I get your point.

Actually the line was

Http list(few parameters);

Http list(few parameters);

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but I removed them to make the example look simple.

Sorry, It was my mistake.

Thanks for your time and advice.
Thanks a lot.