Question

我正在使用带有C ++和boost :: thread_group的线程池，但在线程中调用方法'widgetProcessorJob'获取一个空参数（小部件）。我尝试以不同的方式制作它，我认为我正在使用boost :: asio严重... 我正在寻找一个可以告诉我我做错了什么以及哪种方式最好的方法？

void MarketingAutomation::processOnWidgets() {
    boost::asio::io_service ioService;
    boost::thread_group threadpool;
    bool available = true; // need infinite loop in my program
    int offset = 0; // Only for batching

    boost::asio::io_service::work work(ioService);
    for (int i = 0; i < _poolSize; i++) {
        threadpool.create_thread(boost::bind(&boost::asio::io_service::run, &ioService));
    }

    while (available) {
        std::shared_ptr<sql::ResultSet> widgets(MyDBConnector::getInstance().getWidgets(_batchSize, offset)); // just getting some data from sql base with mysqlcppconn

        if (!widgets->next()) {
            offset = 0;
            Logger::getInstance().logSTD("Restart widgets iteration !"); // this part is called when i did stuff on all batches
        } else {

            Logger::getInstance().logSTD("Proccess on " + std::to_string((offset / _batchSize) + 1) + " batch");

            // loop through the batch
            while (!widgets->isAfterLast()) {
                ioService.post(boost::bind(&MarketingAutomation::widgetProcessorJob, this, widgets));
                widgets->next();
            }

            threadpool.join_all();
            Logger::getInstance().logSTD("Finish on " + std::to_string((offset / _batchSize) + 1) + " batch");
            offset += _batchSize;

        }
    }
}

// Here is the function called in thread
void MarketingAutomation::widgetProcessorJob(std::shared_ptr<sql::ResultSet> widget) {
    WidgetProcessor widgetProcessor(widget, _kind); // Here widget is already null, but why ? :'(
    widgetProcessor.processOnWidget();
}

Answer 1

// loop through the batch
while (!widgets->isAfterLast()) {
    ioService.post(boost::bind(&MarketingAutomation::widgetProcessorJob, this, widgets));
    widgets->next();
}

您只有一个std::shared_ptr<sql::ResultSet> widgets。通过多次发布它来制作智能指针的副本，但所有这些智能指针都指向相同的基础sql::ResultSet。这意味着当你致电next()时，你正在＆＃34; nexting＆＃34;您发布给所有处理程序的记录集。

现在，根据线程的执行时间和不同的竞争条件，你甚至可以在任何处理程序被调用之前到达记录集的末尾，即使不是这种情况，你也处于竞争条件会让你充其量只是你想要的一部分。

Answer 2

正如我以为我使用了boost :: asio！发布后我尝试了我的程序，没有无限循环'可用'，并且使用ioService运行的作业进行了无限循环，因为我从未调用过stop方法。为了得到正确答案，我移动了thread_pool＆amp; 'available'循环中的io_service声明/定义，并在每次迭代时调用stop！这是正确的答案，包括@Drax答案：

void MarketingAutomation::processOnWidgets() {
    bool available = true;
    int offset = 0;


    while (available) {
        std::shared_ptr<sql::ResultSet> widgets(SlaaskDBConnector::getInstance().getWidgets(_batchSize, offset));

        if (!widgets->next()) {
            offset = 0;
            Logger::getInstance().logSTD("Restart widgets iteration !");
        } else {

            boost::asio::io_service ioService;
            boost::thread_group threadpool;

            boost::asio::io_service::work work(ioService);
            for (int i = 0; i < _poolSize; i++) {
                threadpool.create_thread(boost::bind(&boost::asio::io_service::run, &ioService));
        }

            Logger::getInstance().logSTD("Proccess on " + std::to_string((offset / _batchSize) + 1) + " batch");

            while (!widgets->isAfterLast()) {
                ioService.post(boost::bind(&MarketingAutomation::widgetProcessorJob, this, widgets->getInt("id")));
                widgets->next();
        }

            ioService.stop();
            threadpool.join_all();
            Logger::getInstance().logSTD("Finish on " + std::to_string((offset / _batchSize) + 1) + " batch");
            offset += _batchSize;

        }
    }
}

void MarketingAutomation::widgetProcessorJob(int widgetID) {
    WidgetProcessor widgetProcessor(widgetID, _kind); // Here widget is already null, but why ? :'(
    widgetProcessor.processOnWidget();
}

作为boost :: thread_group中调用的成员函数的参数给出的指针为null

2 个答案: