【后台开发】TinyWebser学习笔记（2）线程池、数据库连接池

template <typename T>
class threadpool
{
public:
    /*thread_number是线程池中线程的数量，max_requests是请求队列中最多允许的、等待处理的请求的数量*/
    threadpool(int actor_model, connection_pool *connPool, int thread_number = 8, int max_request = 10000);
    ~threadpool();
    bool append(T *request, int state);
    bool append_p(T *request);

private:
    /*工作线程运行的函数，它不断从工作队列中取出任务并执行之*/
    static void *worker(void *arg);//为什么要用静态成员函数呢？
    void run();

private:
    int m_thread_number;        //线程池中的线程数
    int m_max_requests;         //请求队列中允许的最大请求数
    pthread_t *m_threads;       //描述线程池的数组，其大小m_thread_number
    std::list<T *> m_workqueue; //请求队列
    locker m_queuelocker;       //保护请求队列的互斥锁
    sem m_queuestat;            //是否有任务需要处理
    connection_pool *m_connPool;  //数据库
    int m_actor_model;          //模型切换（这个切换是指？）
};
template <typename T>
threadpool<T>::threadpool( int actor_model, connection_pool *connPool, int thread_number, int max_requests) : m_actor_model(actor_model),m_thread_number(thread_number), m_max_requests(max_requests), m_threads(NULL),m_connPool(connPool)
{
    if (thread_number <= 0 || max_requests <= 0)
        throw std::exception();
    m_threads = new pthread_t[m_thread_number];     //pthread_t是长整型
    if (!m_threads)
        throw std::exception();
    for (int i = 0; i < thread_number; ++i)
    {
        if (pthread_create(m_threads + i, NULL, worker, this) != 0)
        {   //线程创建成功则返回0，如线程池创建失败则应关闭线程池
            delete[] m_threads;
            throw std::exception();
        }
        if (pthread_detach(m_threads[i])) //主要是将线程属性更改为unjoinable，便于资源的释放，详见PPPPS
        {
            delete[] m_threads;
            throw std::exception();
        }
    }
}
template <typename T>
threadpool<T>::~threadpool()
{
    delete[] m_threads;
}
template <typename T>
bool threadpool<T>::append(T *request, int state)
{
    m_queuelocker.lock();
    if (m_workqueue.size() >= m_max_requests)
    {
        m_queuelocker.unlock();
        return false;
    }
    request->m_state = state;
    m_workqueue.push_back(request);
    m_queuelocker.unlock();
    m_queuestat.post();
    return true;
}
template <typename T>
bool threadpool<T>::append_p(T *request)
{
    m_queuelocker.lock();
    if (m_workqueue.size() >= m_max_requests)
    {
        m_queuelocker.unlock();
        return false;
    }
    m_workqueue.push_back(request);
    m_queuelocker.unlock();
    m_queuestat.post();
    return true;
}
template <typename T>
void *threadpool<T>::worker(void *arg)
{
    threadpool *pool = (threadpool *)arg;
    pool->run();
    return pool;
}
template <typename T>
void threadpool<T>::run()
{
    while (true)
    {
        m_queuestat.wait();
        m_queuelocker.lock();
        if (m_workqueue.empty())
        {
            m_queuelocker.unlock();
            continue;
        }
        T *request = m_workqueue.front();
        m_workqueue.pop_front();
        m_queuelocker.unlock();
        if (!request)
            continue;
        if (1 == m_actor_model)
        {
            if (0 == request->m_state)
            {
                if (request->read_once())
                {
                    request->improv = 1;
                    connectionRAII mysqlcon(&request->mysql, m_connPool);
                    request->process();
                }
                else
                {
                    request->improv = 1;
                    request->timer_flag = 1;
                }
            }
            else
            {
                if (request->write())
                {
                    request->improv = 1;
                }
                else
                {
                    request->improv = 1;
                    request->timer_flag = 1;
                }
            }
        }
        else
        {
            connectionRAII mysqlcon(&request->mysql, m_connPool);
            request->process();
        }
    }
}

class connection_pool
{
public:
    MYSQL *GetConnection();              //获取数据库连接
    bool ReleaseConnection(MYSQL *conn); //释放连接
    int GetFreeConn();                   //获取连接
    void DestroyPool();                  //销毁所有连接

    //单例模式 这个是利用局部静态变量懒汉模式实现单例（多线程不友好）
    //对于多线程而言，多个线程可能同时访问到该静态变量，并发现其没有被初始化（C++实现机制是）
    //（该看静态变量内部一标志位是为1，为1则说明已被初始化）
    //多个线程同时判定其没有初始化而后均初始化就会造成错误（即它不是一个原子操作）
    static connection_pool *GetInstance();

    void init(string url, string User, string PassWord, string DataBaseName, int Port, int MaxConn, int close_log); 

private:
    connection_pool();
    ~connection_pool();

    int m_MaxConn;  //最大连接数
    int m_CurConn;  //当前已使用的连接数
    int m_FreeConn; //当前空闲的连接数
    locker lock;
    list<MYSQL *> connList; //连接池
    sem reserve;

public:
    string m_url;            //主机地址
    string m_Port;       //数据库端口号
    string m_User;       //登陆数据库用户名
    string m_PassWord;   //登陆数据库密码
    string m_DatabaseName; //使用数据库名
    int m_close_log;    //日志开关
};

class connectionRAII{

public:
    connectionRAII(MYSQL **con, connection_pool *connPool);
    ~connectionRAII();
    
private:
    MYSQL *conRAII;
    connection_pool *poolRAII;
};