SQLAlchemy和Falcon-会话初始化

问题描述

我想知道最好的地方是在falcon中创建一个有范围的会话.

I'm wondering where the best place would be to create a scoped session for use in falcon.

通过阅读flask-sqlalchemy代码，它以某种方式进行了如下操作:

From reading the flask-sqlalchemy code, it, in a round about way, does something like this:

from sqlalchemy import create_engine
from sqlalchemy.orm import scoped_session, sessionmaker

try:
    from greenlet import get_current as get_ident
except ImportError:
    try:
        from thread import get_ident
    except ImportError:
        from _thread import get_ident

connection_uri = 'postgresql://postgres:@localhost:5432/db'
engine = create_engine(connection_uri)
session_factory = sessionmaker(bind=engine)
session_cls = scoped_session(session_factory, scopefunc=get_ident)
session = session_cls()

这对猎鹰有用吗? get_ident func在使用Gunicorn时会做正确的事"吗?

Would this work for falcon? Will the get_ident func "do the right thing" when using gunicorn?

推荐答案

您可以使用中间件

示例.

1. 创建引擎，session_factory和scoped_session对象.

1. Create engine, session_factory and scoped_session object.

from sqlalchemy import create_engine
from sqlalchemy.orm import scoped_session
from sqlalchemy.orm import sessionmaker

import settings


engine = create_engine(
    '{engine}://{username}:{password}@{host}:{port}/{db_name}'.format(
    **settings.POSTGRESQL
    )
)

session_factory = sessionmaker(bind=engine)
Session = scoped_session(session_factory)

创建中间件.

Create middleware.

class SQLAlchemySessionManager:
    """
    Create a scoped session for every request and close it when the request
    ends.
    """

    def __init__(self, Session):
        self.Session = Session

    def process_resource(self, req, resp, resource, params):
        resource.session = self.Session()

    def process_response(self, req, resp, resource, req_succeeded):
        if hasattr(resource, 'session'):
            Session.remove()

注册中间件.

Register middleware.

import falcon


app = falcon.API(middleware=[
    SQLAlchemySessionManager(Session),
])

在每个请求中都可以访问会话.

Session is accessible in every request.

import falcon


class MyAPI:

    def on_get(self, req, resp):
        # You can access self.session here
        # self.session.add(foo)
        # self.session.commit()

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