Flask请求扩展和数据库连接池

#!/usr/bin/env python
# -*- coding:utf-8 -*-
from flask import Flask, Request, render_template

app = Flask(__name__, template_folder='templates')
app.debug = True


@app.before_first_request
def before_first_request1():
    print('before_first_request1')


@app.before_first_request
def before_first_request2():
    print('before_first_request2')


@app.before_request
def before_request1():
    Request.nnn = 123
    print('before_request1')


@app.before_request
def before_request2():
    print('before_request2')


@app.after_request
def after_request1(response):
    print('before_request1', response)
    return response


@app.after_request
def after_request2(response):
    print('before_request2', response)
    return response


@app.errorhandler(404)
def page_not_found(error):
    return 'This page does not exist', 404


@app.template_global()
def sb(a1, a2):
    return a1 + a2


@app.template_filter()
def db(a1, a2, a3):
    return a1 + a2 + a3


@app.route('/')
def hello_world():
    return render_template('hello.html')


if __name__ == '__main__':
    app.run()

@app.before_request
def process_request(*args,**kwargs):
    #登录页面不需要验证
    if request.path == '/login':
        return None
    user = session.get('user_info')
    if user:
        return None
    return redirect('/login')

from flask import Flask,render_template,request,redirect,session,url_for

app = Flask(__name__)
app.debug = True
app.secret_key = 'abcdef'



@app.before_request
def process_request1(*args,**kwargs):
    print('request1进来')

@app.before_request
def process_request2(*args,**kwargs):
    print('request2进来')

@app.after_request
def process_response1(response):
    print('response1走了')
    return response

@app.after_request
def process_response2(response):
    print('response2走了')
    return response

@app.route('/index',methods=['GET'])
def index():
    print('index函数')
    return 'hello'

if __name__ == '__main__':
    app.run()

@app.before_request
def process_request1(*args,**kwargs):
    print('request1进来')
    return "拦截"

@app.errorhandler(404)
def error_404(arg):
    return '404错误'

POOL = PersistentDB(
    creator=pymysql,  # 使用链接数据库的模块
    maxusage=None,  # 一个链接最多被重复使用的次数，None表示无限制
    setsession=[],  # 开始会话前执行的命令列表。如：["set datestyle to ...", "set time zone ..."]
    ping=0,
    # 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
    closeable=False,
    # 如果为False时， conn.close() 实际上被忽略，供下次使用，再线程关闭时，才会自动关闭链接。如果为True时， conn.close()则关闭链接，那么再次调用pool.connection时就会报错，因为已经真的关闭了连接（pool.steady_connection()可以获取一个新的链接）
    threadlocal=None,  # 本线程独享值得对象，用于保存链接对象，如果链接对象被重置
    host='127.0.0.1',
    port=3306,
    user='root',
    password='123',
    database='pooldb',
    charset='utf8'
)

def func():
    conn = POOL.connection(shareable=False)
    cursor = conn.cursor()
    cursor.execute('select * from tb1')
    result = cursor.fetchall()
    cursor.close()
    conn.close()

func()

import time
import pymysql
import threading
from DBUtils.PooledDB import PooledDB, SharedDBConnection
POOL = PooledDB(
    creator=pymysql,  # 使用链接数据库的模块
    maxconnections=6,  # 连接池允许的最大连接数，0和None表示不限制连接数
    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=5,  # 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。
    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=[],  # 开始会话前执行的命令列表。如：["set datestyle to ...", "set time zone ..."]
    ping=0,
    # 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='127.0.0.1',
    port=3306,
    user='root',
    password='123',
    database='pooldb',
    charset='utf8'
)


def func():
    # 检测当前正在运行连接数的是否小于最大链接数，如果不小于则：等待或报raise TooManyConnections异常
    # 否则
    # 则优先去初始化时创建的链接中获取链接 SteadyDBConnection。
    # 然后将SteadyDBConnection对象封装到PooledDedicatedDBConnection中并返回。
    # 如果最开始创建的链接没有链接，则去创建一个SteadyDBConnection对象，再封装到PooledDedicatedDBConnection中并返回。
    # 一旦关闭链接后，连接就返回到连接池让后续线程继续使用。
    conn = POOL.connection()

    # print(th, '链接被拿走了', conn1._con)
    # print(th, '池子里目前有', pool._idle_cache, '\r\n')

    cursor = conn.cursor()
    cursor.execute('select * from tb1')
    result = cursor.fetchall()
    conn.close()


func()

import pymysql
import threading
from threading import RLock

LOCK = RLock()
CONN = pymysql.connect(host='127.0.0.1',
                       port=3306,
                       user='root',
                       password='123',
                       database='pooldb',
                       charset='utf8')


def task(arg):
    with LOCK:
        cursor = CONN.cursor()
        cursor.execute('select * from tb1')
        result = cursor.fetchall()
        cursor.close()

        print(result)


for i in range(10):
    t = threading.Thread(target=task, args=(i,))
    t.start()