pool = PooledDB(creator=MySQLdb, mincached=0, maxcached=0,
                maxshared=0, maxconnections=0,
                blocking=False,maxusage=None,
                setsession=None, reset=True,
                failures=None, ping=1,
                *args, **kwargs)

#creator => 任何符合DB-API 2.0規(guī)范的函數(shù)或者兼容的數(shù)據(jù)庫模塊

#mincached => 初始化時，鏈接池中至少創(chuàng)建的空閑的鏈接，0表示不創(chuàng)建

#maxcached => 鏈接池中最大閑置的鏈接數(shù)(0和None不限制)

#maxshared =>  maximum number of shared connections
            (0 or None means all connections are dedicated)
            When this maximum number is reached, connections are
            shared if they have been requested as shareable

#maxconnections => 允許的最大鏈接數(shù)(0或None表示不限制)

#blocking => 鏈接池沒有可用鏈接后，是否阻塞等待。
             True表示阻塞等待,直到獲取到鏈接;
             False不等待,拋異常退出

#maxusage => 同一個鏈接最多被重復(fù)使用的次數(shù)(0和None表示無限制）

#setsession => 可選的會話命令：開始會話前執(zhí)行的命令列表。
例如["set datestyle to…"，"set time zone…"]

#reset => 當(dāng)連接放回池中時，重置連接的方式，默認為True。
          False或者None表示使用begin()開啟了事務(wù)的鏈接，會執(zhí)行回滾;
          安全起見,建議使用True,當(dāng)為True時表示所有鏈接都執(zhí)行回滾操作

#failures => 當(dāng)默認的(OperationalError,InternalError)異常不能滿足要求時,
             可以自定義拋出異常:默認為None;
             自定義為傳入的為tuple或者issubclass(failures, Exception)

#ping => 檢查連接是否仍然處于活動狀態(tài)的方式
         0 = None = never, 
         1 = default = whenever fetched from the pool,
         2 = when a cursor is created, 
         4 = when a query is executed,
         7 = always, and all other bit combinations of these values

#args, kwargs => 傳遞給creator的參數(shù)

# -*- coding: utf-8 -*-
# @Time    : 2020/1/26 0026 20:28
# @Email   : lofish@foxmail.com(擼小魚)
import MySQLdb
import MySQLdb.cursors
from DBUtils.PooledDB import PooledDB
import datetime
class DbManager(object):
    def __init__(self, host, port, db_name, user_name, password):
        cmds = ["set names utf8mb4;"]
        conn_args = {'host': host,
                     'port': port,
                     'db': db_name,
                     'user': user_name,
                     'passwd': password,
                     'charset': 'utf8',
                     'cursorclass': MySQLdb.cursors.DictCursor
                     }
        #  初始化時，鏈接池中至少創(chuàng)建的空閑的鏈接，0表示不創(chuàng)建,mincached: 5
        #  鏈接池中最大閑置的鏈接數(shù)(0和None不限制): 20
        self._pool = PooledDB(MySQLdb, mincached=5, maxcached=20, setsession=cmds, **conn_args)
    def connection(self):
        return self._pool.connection()
_db_manager = None
def create_db_manager(host, port, dbname, username, password):
    global _db_manager
    if _db_manager is None:
        _db_manager = DbManager(host, port, dbname, username, password)
    return _db_manager