Celery延迟任务中的SQLAlchemy会话处理 [英] SQLAlchemy session handling in delayed Celery tasks

问题描述

我正在通过SQLAlchemy使用关系数据库.我想产生一个使用Celery处理数据库的工作.有一个代码:

I am using a relational database via SQLAlchemy. I want to spawn a job that deals with databases using Celery. There is a code:

from sqlalchemy.orm.session import Session
from celery.task import task
from myapp.user import User

@task
def job(user):
    # job...
    session = Session.object_session(user)
    with user.begin():
        user.value = result_value

def ordinary_web_request_handler(uid):
    assert isinstance(session, Session)
    user = session.query(User).get(int(uid))
    # deals with user...
    job.delay(user)
    return response

我需要在延迟的 job 中使用SQLAlchemy会话，但是还没有 session .如何将会话设置为传递的 user 实体?

I need to use a SQLAlchemy session in the delayed job, but there’s no session yet. How can I set a session into passed user entity?

我有很多想法，但是我不确定哪种方法(或没有一种方法)是最佳实践:

There are ways I thought, but I am not sure which of these (or none of these) is the best practice:

• 始终仅传递主键，并通过传递的主键检索新实例.
• 设置传递的实例的会话(但我不知道如何).
• 请勿在延迟的任务中使用ORM.

推荐答案

您应该能够使用辅助信号启动会话:

You should be able to initiate your session with the worker signals: http://celery.readthedocs.org/en/latest/userguide/signals.html#worker-signals

如果您使用类似单例的模式来确保在该线程中始终有可用的会话，那么一切都会正常进行.

If you use a singleton-like pattern to make sure you always have a session available in that thread than everything should work just fine.

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