fabianlindfors / reshape-python

A Python helper library for applications using Reshape

Reshape Python helper

This is a Python helper library for the automated, zero-downtime schema migration tool Reshape. To achieve zero-downtime migrations, Reshape requires that your application runs a simple query when it opens a connection to the database to select the right schema. This library automates that process with a simple method which will return the correct query for your application. It also works great with Django!

Installation

pip install reshape-helper

Usage

The library includes a schema_query method which will find all your Reshape migration files and determine the right schema query to run. Here's an example of how to use it:

import schema_query from reshape_helper

# Run the schema query against your database when you open a new connection
db.execute(schema_query())

By default, schema_query will look for migrations files in migrations/, but you can specify your own directories as well:

import schema_query from reshape_helper

query = schema_query(
	"src/users/migrations",
	"src/todos/migrations",
)

Usage with Django

Using Reshape for zero-downtime migrations with Django is really simple. After installing reshape_helper, update your app.py and add a handler for the connection_created signal. This handler will run the schema query whenever a new database connection is opened:

from django.db.backends.signals import connection_created
import schema_query from reshape_helper

class YourAppConfig(AppConfig):
	def ready(self):
		connection_created.connect(new_connection_handler)

def new_connection_handler(sender, connection, **kwargs):
	connection.cursor().execute(schema_query())

Now your Django app is ready for use with Reshape. Rather than creating standard Django migrations, you should create Reshape migration files in migrations/. If you'd prefer to use other folders for your migrations, you can pass them to schema_query():

def new_connection_handler(sender, connection, **kwargs):
	connection.cursor().execute(schema_query("yourapp/users/migrations", "yourapp/todo/migrations"))

License

Released under the MIT license.