# coding:utf-8

import threading

import pymysql

from DBUtils.PooledDB import PooledDB

from app.common.file_config import get_config

class DbPool(object):

    _instance_lock = threading.Lock()

    def __init__(self):

        if not hasattr(DbPool, "pool"):

            DbPool.mysql_pool()

        else:

            pass

    def __new__(cls, *args, **kwargs):

        if not hasattr(DbPool, "_instance"):

            with DbPool._instance_lock:

                if not hasattr(DbPool, "_instance"):

                    DbPool._instance = object.__new__(cls, *args, **kwargs)

        return DbPool._instance

    @staticmethod

    def mysql_pool():

        host = get_config('database', 'MYSQL_HOST')

        port = int(get_config('database', 'MYSQL_PORT'))

        user = get_config('database', 'MYSQL_USERNAME')

        passwd = get_config('database', 'MYSQL_PASSWORD')

        db = get_config('database', 'MYSQL_DB')

        DbPool.pool = PooledDB(

            creator=pymysql,  # 使用链接数据库的模块

            mincached=2,  # 初始化时，链接池中至少创建的空闲的链接，0表示不创建

            maxcached=6,  # 链接池中最多闲置的链接，0和None不限制

            maxshared=3,

            # 链接池中最多共享的链接数量，0和None表示全部共享。PS: 无用，因为pymysql和MySQLdb等模块的 threadsafety都为1，所有值无论设置为多少，_maxcached永远为0，所以永远是所有链接都共享。

            maxconnections=8,  # 连接池允许的最大连接数，0和None表示不限制连接数

            blocking=True,  # 连接池中如果没有可用连接后，是否阻塞等待。True，等待；False，不等待然后报错

            maxusage=None,  # 一个链接最多被重复使用的次数，None表示无限制

            setsession=None,  # 开始会话前执行的命令列表。如：["set datestyle to ...", "set time zone ..."]

            # ping MySQL服务端，检查是否服务可用。# 如：0 = None = never, 1 = default = whenever it is requested, 2 = when a cursor is created, 4 = when a query is executed, 7 = always

            host=host,

            port=port,

            user=user,

            passwd=passwd,

            db=db,

            use_unicode=False,

            charset='utf8'

        )