Question

我正在尝试使用flask g对象共享一个打开的数据库连接，并在用户登录时保持打开状态。我遇到的问题是看起来像函数get_db（）isn不是每次有新的页面请求时都使用当前打开的连接而是打开一个新连接？

每次进入新页面时，如何才能打开新请求？

数据库文件（qry由其他模块导入）：

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

import os
import json
import psycopg2
import psycopg2.extras
from flask import g
from urllib import parse

from lingco import app


def load_row(row):
    loaded = {}
    for k, v in row.items():
        loaded[k] = json.loads(v) if type(v) == str else v
    return loaded

def connect_db():
    parse.uses_netloc.append("postgres")
    if "DATABASE_URL" in os.environ:
        url = parse.urlparse(os.environ["DATABASE_URL"])
    else:
        url = parse.urlparse(app.config["DATABASE_URL"])
    conn = psycopg2.connect(
        database=url.path[1:],
        user=url.username,
        password=url.password,
        host=url.hostname,
        port=url.port
        )
    print("***OPENING CONNECTION***")
    return conn


@app.teardown_appcontext
def close_db(error):
    """Closes the database again at the end of the request 
    if user is not logged in."""
    if hasattr(g, 'db_conn') and not hasattr(g, 'user'):
        print("***CLOSING CONNECTION***")
        g.db_conn.close()
        g.pop('db_conn', None)


def get_db():
    """Opens a new database connection if there is none yet for the
    current application context.
    """
    if not hasattr(g, 'db_conn'):
        g.db_conn = connect_db()
    return g.db_conn


def qry(query="",args=(),**kwargs):
    conn = get_db()
    cursor = conn.cursor(cursor_factory=psycopg2.extras.RealDictCursor)
    cursor.execute(query,args)
    if "commit" in kwargs and kwargs["commit"]==True:
        conn.commit()
    if "fetch" in kwargs and kwargs["fetch"]=="rowcount":
        return cursor.rowcount
    if "fetch" in kwargs and kwargs["fetch"]=="all":
        records = cursor.fetchall()
        if "load"in kwargs and kwargs["load"]==True:
            loaded_records = []
            for row in records:
                loaded_records.append(load_row(row))
            return loaded_records
        return records
    if "fetch" in kwargs and kwargs["fetch"]=="one":
        record = cursor.fetchone()
        if "load"in kwargs and kwargs["load"]==True:
            record = load_row(record)
        if "attr" in kwargs:
            return record[kwargs["attr"]]
        return record

终端输出：

host-162571:flask_try sethkillian$ python run.py
 * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
 * Restarting with stat
 * Debugger is active!
 * Debugger PIN: 692-579-362
127.0.0.1 - - [25/Jan/2018 16:28:51] "GET /login HTTP/1.1" 200 -
***OPENING CONNECTION***
127.0.0.1 - - [25/Jan/2018 16:29:01] "POST /login HTTP/1.1" 302 -
***OPENING CONNECTION***
127.0.0.1 - - [25/Jan/2018 16:29:01] "GET /dashboard/ HTTP/1.1" 200 -
***OPENING CONNECTION***
127.0.0.1 - - [25/Jan/2018 16:29:07] "GET /dashboard/2/roster HTTP/1.1" 200 -
***OPENING CONNECTION***
127.0.0.1 - - [25/Jan/2018 16:29:13] "GET /dashboard/ HTTP/1.1" 200 -
***OPENING CONNECTION***
127.0.0.1 - - [25/Jan/2018 16:29:18] "GET /questions HTTP/1.1" 200 -
***OPENING CONNECTION***
127.0.0.1 - - [25/Jan/2018 16:29:20] "GET /static/js/question_database.js HTTP/1.1" 200 -
***OPENING CONNECTION***
127.0.0.1 - - [25/Jan/2018 16:29:34] "GET / HTTP/1.1" 200 -
***OPENING CONNECTION***
***CLOSING CONNECTION***
127.0.0.1 - - [25/Jan/2018 16:29:39] "GET /logout HTTP/1.1" 302 -
127.0.0.1 - - [25/Jan/2018 16:29:39] "GET / HTTP/1.1" 200 -
127.0.0.1 - - [25/Jan/2018 16:29:43] "GET /dashboard/ HTTP/1.1" 302 -
127.0.0.1 - - [25/Jan/2018 16:29:43] "GET /login HTTP/1.1" 200 -

Answer 1

g对象仅对当前请求上下文是全局的。这意味着当同一用户发送新请求时，新请求具有自己的g对象。

拥有全局连接对象的一种解决方案：如果要确保只有一个连接对象，只需使用普通的全局对象和一些簿记。

conn = None

def get_db():
    global conn
    if conn is None:
        conn = connect_db()
    return conn

在Flask g中存储Postgres连接

1 个答案: