Flask中的數據鏈接池

pymsql連接數據庫

import pymysql

conn = pymysql.connect(host='127.0.0.1', port=3306, user='root', passwd='123456', db='s8day127db')
cursor = conn.cursor(cursor=pymysql.cursors.DictCursor)
# cursor.execute("select id,name from users where name=%s and pwd=%s",['lqz','123',])
cursor.execute("select id,name from users where name=%(user)s and pwd=%(pwd)s",{'user':'lqz','pwd':'123'})
obj = cursor.fetchone()
conn.commit()
cursor.close()
conn.close()

print(obj)

數據庫鏈接池版

方式一:

爲每一個線程建立一個鏈接,線程即便調用了close方法,也不會關閉,只是把鏈接從新放到鏈接池,供本身線程再次使用。當線程終止時,鏈接自動關閉python

from DBUtils.PersistentDB import PersistentDB
import pymysql
POOL = PersistentDB(
    creator=pymysql,  # 使用連接數據庫的模塊
    maxusage=None,  # 一個連接最多被重複使用的次數,None表示無限制
    setsession=[],  # 開始會話前執行的命令列表。
    ping=0,
    # ping MySQL服務端,檢查是否服務可用。
    closeable=False,
    # 若是爲False時, conn.close() 實際上被忽略,供下次使用,再線程關閉時,纔會自動關閉連接。若是爲True時, conn.close()則關閉連接,那麼再次調用pool.connection時就會報錯,由於已經真的關閉了鏈接(pool.steady_connection()能夠獲取一個新的連接)
    threadlocal=None,  # 本線程獨享值得對象,用於保存連接對象,若是連接對象被重置
    host='127.0.0.1',
    port=3306,
    user='root',
    password='123456',
    database='test',
    charset='utf8'
)

def func():
    conn = POOL.connection(shareable=False)
    cursor = conn.cursor()
    cursor.execute('select * from user')
    result = cursor.fetchall()
    print(result)
    cursor.close()
    conn.close()
if __name__ == '__main__':

    func()

方式二:

模式二:建立一批鏈接到鏈接池,供全部線程共享使用mysql

setting.pyredis

from datetime import timedelta
from redis import Redis
import pymysql
from DBUtils.PooledDB import PooledDB, SharedDBConnection

class Config(object):
    DEBUG = True
    SECRET_KEY = "umsuldfsdflskjdf"
    PERMANENT_SESSION_LIFETIME = timedelta(minutes=20)
    SESSION_REFRESH_EACH_REQUEST= True
    SESSION_TYPE = "redis"
    PYMYSQL_POOL = PooledDB(
        creator=pymysql,  # 使用連接數據庫的模塊
        maxconnections=6,  # 鏈接池容許的最大鏈接數,0和None表示不限制鏈接數
        mincached=2,  # 初始化時,連接池中至少建立的空閒的連接,0表示不建立
        maxcached=5,  # 連接池中最多閒置的連接,0和None不限制
        maxshared=3,
        # 連接池中最多共享的連接數量,0和None表示所有共享。PS: 無用,由於pymysql和MySQLdb等模塊的 threadsafety都爲1,全部值不管設置爲多少,_maxcached永遠爲0,因此永遠是全部連接都共享。
        blocking=True,  # 鏈接池中若是沒有可用鏈接後,是否阻塞等待。True,等待;False,不等待而後報錯
        maxusage=None,  # 一個連接最多被重複使用的次數,None表示無限制
        setsession=[],  # 開始會話前執行的命令列表。如:["set datestyle to ...", "set time zone ..."]
        ping=0,
        # ping MySQL服務端,檢查是否服務可用。# 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='127.0.0.1',
        port=3306,
        user='root',
        password='123456',
        database='s8day127db',
        charset='utf8'
    )

class ProductionConfig(Config):
    SESSION_REDIS = Redis(host='192.168.0.94', port='6379')



class DevelopmentConfig(Config):
    SESSION_REDIS = Redis(host='127.0.0.1', port='6379')


class TestingConfig(Config):
    pass

utils/sql.pysql

import pymysql
from settings import Config
class SQLHelper(object):

    @staticmethod
    def open(cursor):
        POOL = Config.PYMYSQL_POOL
        conn = POOL.connection()
        cursor = conn.cursor(cursor=cursor)
        return conn,cursor

    @staticmethod
    def close(conn,cursor):
        conn.commit()
        cursor.close()
        conn.close()

    @classmethod
    def fetch_one(cls,sql,args,cursor =pymysql.cursors.DictCursor):
        conn,cursor = cls.open(cursor)
        cursor.execute(sql, args)
        obj = cursor.fetchone()
        cls.close(conn,cursor)
        return obj

    @classmethod
    def fetch_all(cls,sql, args,cursor =pymysql.cursors.DictCursor):
        conn, cursor = cls.open(cursor)
        cursor.execute(sql, args)
        obj = cursor.fetchall()
        cls.close(conn, cursor)
        return obj

使用:數據庫

obj = SQLHelper.fetch_one("select id,name from users where name=%(user)s and pwd=%(pwd)s", form.data)
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