C++ | 实现mysql连接池

利用单利模式获取连接池实例,支持高并发,为每个连接记录存活时间,当连接总量大于最大连接数时会将时间过长的连接断开,当池子没有连接时会利用生产者线程进行生产

Connpool *Connpool::instance = nullptr;
//获得池子
Connpool *Connpool::GetInstance()
{
    if (instance == nullptr)
    {
        std::lock_guard lock(instance_mutex);
        if (instance == nullptr)
        {
            instance = new Connpool();
        }
    }
    return instance;
}
void Connpool::create_new_conn()
{
    MySQL *p = new MySQL();
    p->connect();
    p->refreshAliveTime();
    conn_que.push(p);
    ++count_con;
}
//池子初始化
Connpool::Connpool() : count_con(0)
{
    for (int i = 0; i < INIT_SIZE; ++i)
    {
        create_new_conn();
    }
    
    std::thread p(bind(&Connpool::produceConnectionTask,this));
    p.detach();
}
//获取一个sql连接
shared_ptr Connpool::GetConn()
{
    unique_lock lock(_mutex);
    while (conn_que.empty())
    {
        cv_produ.notify_all();
        cv_cust.wait(lock);
    }
        while (count_con > MAX_SIZE)
    {
        MySQL *p = conn_que.front();
        if (p->getAliveTime() >= (MAX_TIME * 1000))
        {
            conn_que.pop();
            count_con--;
            // 调用~Connection()释放连接
            delete p;
        }
        else
        {
            // 如果队头的连接没有超过_maxIdleTime，其他连接肯定没有
            break;
        }
    }
    
    shared_ptr sp(conn_que.front(),
                         [&](MySQL *p)
                         {
                             unique_lock lock(_mutex);
                             p->refreshAliveTime();
                             conn_que.push(p);
                         });
    conn_que.pop();
    return sp;
}

void Connpool::produceConnectionTask()
{
    while (1)
    {
        unique_lock lock(_mutex);
        while (!conn_que.empty())
        {
            cv_produ.wait(lock);
        }
        create_new_conn();
        cv_cust.notify_all();
    }
}

这里的MySQL是自己对数据库操作的封装类