在 python 中将连接对象从进程传递到主进程

Question

我有一个按需创建数据库连接的应用程序。但我想要一个功能，如果创建连接花费的时间超过一定时间，它应该超时。所以我用多进程，来生成一个进程，并在一定时间后加入它，并检查进程的状态。此过程运行良好，但我无法从中检索连接对象生成的进程，因为它不可序列化。有什么帮助吗？

import psycopg2
import multiprocessing
from multiprocessing import Process
config = {
    "user": "xxx",
    "password": "xxx",
    "host": "xxx",
    "database": "xxx",
}

def create_postgres_connection(config, return_dict):
    # Connect to the database, we have to timeout this function if it takes too long.
    host = config['host']
    database = config['database']
    username = config['user']
    password = config['password']
    connection = psycopg2.connect(host=host, database=database, user=username, password=password)
    return_dict['connection'] = connection

def run_with_limited_time(func, args, kwargs, time):
    """Runs a function with time limit
    :param func: The function to run
    :param args: The functions args, given as tuple
    :param kwargs: The functions keywords, given as dict
    :param time: The time limit in seconds
    :return: True if the function ended successfully. False if it was terminated.
    """
    p = Process(target=func, args=args, kwargs=kwargs)
    p.start()
    p.join(5)
    if p.is_alive():
        p.terminate()
        print('Timed Out')
        return False
    return True

if __name__ == '__main__':
    manager = multiprocessing.Manager()
    return_dict = manager.dict()
    run_with_limited_time(create_postgres_connection, (config, return_dict), {}, 3)
    print(return_dict)

Answer 1

您将无法使用多处理来执行此操作，因为它依赖于 Pickling 对象以便在进程之间传输它。正如您所发现的，连接对象无法腌制。

但是，我认为您无论如何都不需要这样做，因为 Postgres 在连接时允许connect_timeout参数，这确实是您需要解决的问题。connect_timeout以秒为单位指定。[邮政文档]

根据 psycopg2 文档，您可以将任何特定于数据库的参数作为关键字参数传递。

它看起来像这样：

def create_postgres_connection(config, connection):
    # Connect to the database
    host = config['host']
    database = config['database']
    username = config['user']
    password = config['password']
    connection = psycopg2.connect(host=host, database=database, user=username, 
                                  password=password, connect_timeout=3)
    return connection