workerThread calling static QVector - will freeze if not running for many hours

[swankster]

I have a application that parses a UDP stream. Then monitor that stream for a trigger event to start my thread. within that thread is a worker thread that calls a function which contains a static QVector. On every trigger event I initiate a vector.swap and vector.resize/reserve (have used both with same results).

with the program running and continually receiving UDP data. It runs beautifully with not issues. This data is then written to MySQL. a second thread is also running and writing reference data to another table in MySQL. Both MySQL write functions are on separate connections.

However if my program is left running overnight with no UPD stream. My program will hang and must be re-started to work again. This is not the case with 4 hours of no UDP. I have not determined a specific time as of yet. Not sure if my issue id with my Thread or my Vector. The 2nd thread function will pick up and continue to run normally.

Below are a few code snippets.

System Windows 7 Prof.
creator 4.1.0
Qt 5.6.2(Gcc 6.1.0, 64 bit)
using C++11

[Main Thread] 
{
   frmThread = new QThread;
    workerThread = new StreamToVector();
    workerThread->moveToThread(frmThread);
    connect(workerThread, &DataStreamToVector::destroyed, frmThread, &QThread::quit);
    connect(workerThread, &DataStreamToVector::destroyed, workerThread, &DataStreamToVector::deleteLater);
    connect(this, &DataStreamToBuffer::DataToVector_Signal, workerThread, &DataStreamToVector::parseStreamToVector_Slot, Qt::DirectConnection);
    frmThread->start();
 
    DataToVector_Signal(dataStream, dataSize, RecordsPerTriggerEvent);
}
 
[worker thread  .h ]
    QThread *frmThread;
 
[worker thread  .cpp ]
void DataStreamToVector::parseStreamToVector_Slot(QString dataStream, int dataSize, uint RecordsPerTriggerEvent)
{
    static QVector < QVector<QString> > cycleBuffer(63, QVector<QString>(MAX_CYCLE_SIZE_x10MS));
    static uint recordCnt = 1;
 
    if ( recordCnt > RecordsPerTriggerEvent ) {
        QVector < QVector<QString> > defaultBuffer(63, QVector<QString>(MAX_CYCLE_SIZE_x10MS));
        recordCnt = 1;
        cycleBuffer.swap(defaultBuffer);
        cycleBuffer.reserve(GALIL_40x0_ADDRESS_COUNT);
    }
 
    if ( recordCnt <= recPerCycle ) {
        cycleBuffer[0][recordCnt].append(dataStream.mid( 12,2 )); // general Input Block 0 address
        cycleBuffer[1][recordCnt].append(dataStream.mid( 14,2 ));
        // recordCnt typically 350 - 800
 
    if ( recordCnt == RecordsPerTriggerEvent )
            writeRecordsToDB(RecordsPerTriggerEvent, cycleBuffer);
 
    recordCnt++;
}

[Main Thread] 
{
   frmThread = new QThread;
    workerThread = new StreamToVector();
    workerThread->moveToThread(frmThread);
    connect(workerThread, &DataStreamToVector::destroyed, frmThread, &QThread::quit);
    connect(workerThread, &DataStreamToVector::destroyed, workerThread, &DataStreamToVector::deleteLater);
    connect(this, &DataStreamToBuffer::DataToVector_Signal, workerThread, &DataStreamToVector::parseStreamToVector_Slot, Qt::DirectConnection);
    frmThread->start();

    DataToVector_Signal(dataStream, dataSize, RecordsPerTriggerEvent);
}

[worker thread  .h ]
    QThread *frmThread;

[worker thread  .cpp ]
void DataStreamToVector::parseStreamToVector_Slot(QString dataStream, int dataSize, uint RecordsPerTriggerEvent)
{
    static QVector < QVector<QString> > cycleBuffer(63, QVector<QString>(MAX_CYCLE_SIZE_x10MS));
    static uint recordCnt = 1;

    if ( recordCnt > RecordsPerTriggerEvent ) {
        QVector < QVector<QString> > defaultBuffer(63, QVector<QString>(MAX_CYCLE_SIZE_x10MS));
        recordCnt = 1;
        cycleBuffer.swap(defaultBuffer);
        cycleBuffer.reserve(GALIL_40x0_ADDRESS_COUNT);
    }

    if ( recordCnt <= recPerCycle ) {
        cycleBuffer[0][recordCnt].append(dataStream.mid( 12,2 )); // general Input Block 0 address
        cycleBuffer[1][recordCnt].append(dataStream.mid( 14,2 ));
        // recordCnt typically 350 - 800

    if ( recordCnt == RecordsPerTriggerEvent )
            writeRecordsToDB(RecordsPerTriggerEvent, cycleBuffer);

    recordCnt++;
}

To copy to clipboard, switch view to plain text mode 

any insight or direction would be appreciated. Thank You,

[wysota]

connect(this, &DataStreamToBuffer::DataToVector_Signal, workerThread, &DataStreamToVector::parseStreamToVector_Slot, Qt::DirectConnection);

connect(this, &DataStreamToBuffer::DataToVector_Signal, workerThread, &DataStreamToVector::parseStreamToVector_Slot, Qt::DirectConnection);

To copy to clipboard, switch view to plain text mode 

Why is this a direct connection? This is definitely incorrect as it makes your parseStreamToVector function execute in the main thread instead of the worker thread which is probably not what you want.

[swankster]

I originally had Qt::QueuedConnection and tried direct but forgot to put it back. either way returned the same result.

[wysota]

Please run your application under a debugger. When the freeze occurs, break the application, dump the backtrace and show it to us.

[swankster]

I ran in debug before an it did not fail. Ran it again last night and it did. It appears thread and vector are working fine. It thinks my MySQL table has been truncated.
Thanks for having me check the obvious.

[swankster]

this post is [SOLVED] the issue has nothing to do with QThread or QVector. It is MySQL connection getting hung-up.