Python下Mysql数据连接池——单例

# 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'
        )