塔架:与外部库共享SQLAlchemy MySQL连接 [英] Pylons: Sharing SQLAlchemy MySQL connection with external library

问题描述

我正在使用SQLAlchemy运行Pylons以连接到MySQL，因此，当我想在控制器中使用数据库连接时，可以这样做:

I am running Pylons using SQLAlchemy to connect to MySQL, so when I want to use a database connection in a controller, I can do this:

from myapp.model.meta import Session

class SomeController(BaseController):
    def index(self):
        conn = Session.connection()
        rows = conn.execute('SELECT whatever')
...

说我的控制器需要调用一个外部库，它也需要一个数据库连接，我想从已经建立的SQLAlchemy MySQL连接为其提供连接:

Say my controller needs to call up an external library, that also needs a database connection, and I want to provide the connection for it from the SQLAlchemy MySQL connection that is already established:

from myapp.model.meta import Session

import mymodule

class SomeController(BaseController):
    def index(self):
        conn = Session.connection()
        myobject = mymodule.someobject(DATABASE_OBJECT)
        ...
        conn.close()

DATABSE_OBJECT应该是什么?可能性:

What should DATABSE_OBJECT be? Possibilities:

1. 传递Session-然后在模块代码中打开和关闭Session.connection()
2. 传递conn，然后在控制器中调用conn.close()
3. 只需传递连接参数，并让模块代码设置其自己的连接

1. Pass Session -- and then open and close Session.connection() in the module code
2. Pass conn, and then call conn.close() in the controller
3. Just pass the connection parameters, and have the module code set up its own connection

还有一个难题，那就是我需要实例化app_globals.py中的某些对象，并且这些对象也需要数据库连接.似乎app_globals.py尚不能使用Session的SQLAlchemy连接-尚未绑定.

There is another wrinkle, which is that I need to instantiate some objects in app_globals.py, and these objects need a database connection as well. It seems that app_globals.py cannot use Session's SQLAlchemy connection yet -- it's not bound yet.

我的体系结构从根本上是不完善的吗?我是否应该尝试以这种方式在Pylons和外部库之间共享连接?谢谢！

Is my architecture fundamentally unsounds? Should I not be trying to share connections between Pylons and external libraries this way? Thanks!

推荐答案

您不应该自己管理连接-一切都由SQLAlchemy完成.只需在任何地方使用作用域会话对象，就可以了.

You should not manage connections yourself - it's all done by SQLAlchemy. Just use scoped session object everywhere, and you will be fine.

def init_model(engine):
    sm = orm.sessionmaker(autoflush=False, autocommit=False, expire_on_commit=False, bind=engine)
    meta.engine = engine
    meta.Session = orm.scoped_session(sm)

def index(self):
    rows = Session.execute('SELECT ...')

您可以将Session对象传递到您的外部库，并根据需要在其中进行查询.无需在其上调用.close().

You can pass Session object to your external library and do queries there as you wish. There is no need to call .close() on it.

关于app_globals，我通过在globals类中添加其他方法解决了这一问题，该方法是从environment.py初始化数据库后调用的

Regarding app_globals, I solved that by adding other method in globals class which is called after db initialization from environment.py

class Globals(...):
    def init_model(self, config):
        self.some_persistent_db_object = Session.execute('...')

def load_environment(...):
    ...
    config['pylons.app_globals'].init_model(config)
    return config

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