Flask-CuttlePool 0.1.0

A Flask extension for CuttlePool

Flask-CuttlePool provides a convenient interface for using CuttlePool with Flask.

How-to Guide

If you haven’t read the How-to Guide for CuttlePool, you really should before going any further. FlaskCuttlePool

FlaskCuttlePool should be subclassed in the same way. The only difference in use is how the pool is initialized and how connections are returned to the pool. FlaskCuttlePool accepts retains all the same __init__() parameters as CuttlePool. Assume we have the following pool class (and an app object of course)

import sqlite3

from flask import Flask
from flask_cuttlepool import FlaskCuttlePool

class SQLitePool(FlaskCuttlePool):
     def normalize_connection(self, connection):
         connection.row_factory = None
     def ping(self, connection):
         try:
             rv = connection.execute('SELECT 1').fetchall()
             return (1,) in rv
         except sqlite3.Error:
             return False

app = Flask(__name__)

There are two ways to set up a pool object. On pool initialization

pool = SQLitePool(sqlite3.connect, app=app, database='ricks_lab')

or using init_app() explicitly

pool = SQLitePool(sqlite3.connect, database='ricks_lab')
pool.init_app(app)

init_app() also accepts connection arguments for the underlying SQL driver. So if the database name was stored in app.config and app wasn’t instantiated until after SQLitePool, set up would look like this

pool = SQLitePool(sqlite3.connect)
...  # additional set up code
app = Flask(__name__)
app.from_pyfile('config.cfg')
pool.init_app(app, database=app.config['DATABASE'])

Now the pool can be used as normal. Any calls to get_connection() will store the connection in the application context and the connection will be returned to the pool when the application context is torn down. If a connection is stored on the application context, calls to get_connection() will return that connection. There is no need to call close() on the PoolConnection() object, although it’s ok if the connection is explicitly closed.

If for some reason, you do not want to store the connection on the application context or you need multiple connections at the same time, get_fresh_connection() will get a connection from the pool and won’t store it on the application context. Any connection retrieved from get_fresh_connection() should be explicitly closed.

FAQ

These questions are related to Flask-CuttlePool only, check the FAQ for CuttlePool if you don’t find your answers here.

How do I install it?

pip install git+https://github.com/smitchell556/flask-cuttlepool.git

Contributing

It’s highly recommended to develop in a virtualenv.

Fork the repository.

Clone the repository:

git clone https://github.com/<your_username>/flask-cuttlepool.git

Install the package in editable mode:

cd flask-cuttlepool
pip install -e .[dev]

Now you’re set. See the next section for running tests.

Running the tests

Tests can be run with the command pytest.

Where can I get help?

If you haven’t read the How-to guide above, please do that first. Otherwise, check the issue tracker. Your issue may be addressed there and if it isn’t please file an issue :)