Falcon Middleware: SQLAlchemy Integration
The falcon-sqla package provides a middleware component for managing
SQLAlchemy sessions.
The manager component can also serve as a base building block or a recipe for
more complex use cases, such as applications leveraging multiple database
binds.
Installation
$ pip install falcon-sqlaUsage
The falcon_sqla session Manager can be used in two ways:
- As a Falcon middleware component.
- As a context manager to explicitly provide a database session.
Configuration
- Create a SQLAlchemy engine.
- Pass the engine to the
Manager()initializer as its first parameter. - If using the manager as a middleware component, pass its
middlewareproperty to a falcon.App's middleware list:
engine = create_engine('dialect+driver://my/database')
manager = falcon_sqla.Manager(engine)
app = falcon.App(middleware=[manager.middleware])
# The database session will be available as req.context.sessionContext Manager
A falcon_sqla.Manager can also explicitly provide a database session using
the session_scope() context manager:
# Somewhere inside a responder
with self.manager.session_scope(req, resp) as session:
# Use the session
# <...>session_scope() can also be used as a standalone session context outside of
the request-response cycle:
with self.manager.session_scope() as session:
# Use the session
# <...>Custom Vertical Partitioning
Simple random selection of read- and write- database replicas is supported
out of the box. Use the add_engine() method to instruct the Manager to
include the provided engines in the runtime bind selection logic:
manager = falcon_sqla.Manager(engine)
read_replica = create_engine('dialect+driver://my/database.replica')
manager.add_engine(read_replica, 'r')The Manager.get_bind() method can be overridden to implement custom engine
selection logic for more complex use cases.
See also this SQLAlchemy recipe: Custom Vertical Partitioning.
About Falcon
Falcon is the minimalist REST API and microservices framework for Python developers, with a focus on reliability, correctness, and performance at scale.
About SQLAlchemy
SQLAlchemy is the Python SQL toolkit and Object Relational Mapper that gives application developers the full power and flexibility of SQL.