Question

THIS IS A WIP

Work with Sanic

Using the Sanic extension, the request handler acquires a lazy connection on each request, and return the connection when the response finishes by default.

The lazy connection is actually established if necessary, i.e. just before first access to db.

This behavior is controlled by app.config.DB_USE_CONNECTION_FOR_REQUEST, which is True by default.

Supported configurations:

• DB_HOST

• DB_PORT

• DB_USER

• DB_PASSWORD

• DB_DATABASE

• DB_ECHO

• DB_POOL_MIN_SIZE

• DB_POOL_MAX_SIZE

• DB_USE_CONNECTION_FOR_REQUEST

• DB_KWARGS

An example server:

from sanic import Sanic
from sanic.exceptions import abort
from sanic.response import json
from gino.ext.sanic import Gino

app = Sanic()
app.config.DB_HOST = 'localhost'
app.config.DB_DATABASE = 'gino'
db = Gino()
db.init_app(app)


class User(db.Model):
    __tablename__ = 'users'

    id = db.Column(db.BigInteger(), primary_key=True)
    nickname = db.Column(db.Unicode())

    def __repr__(self):
        return '{}<{}>'.format(self.nickname, self.id)


@app.route("/users/<user_id>")
async def get_user(request, user_id):
    if not user_id.isdigit():
        abort(400, 'invalid user id')
    user = await User.get_or_404(int(user_id))
    return json({'name': user.nickname})


if __name__ == '__main__':
    app.run(debug=True)

Sanic Support

To integrate with Sanic, a few configurations needs to be set in app.config (with default value though):

• DB_HOST: if not set, localhost

• DB_PORT: if not set, 5432

• DB_USER: if not set, postgres

• DB_PASSWORD: if not set, empty string

• DB_DATABASE: if not set, postgres

• DB_ECHO: if not set, False

• DB_POOL_MIN_SIZE: if not set, 5

• DB_POOL_MAX_SIZE: if not set, 10

• DB_KWARGS; if not set, empty dictionary

An example:

from sanic import Sanic
from gino.ext.sanic import Gino

app = Sanic()
app.config.DB_HOST = 'localhost'
app.config.DB_USER = 'postgres'

db = Gino()
db.init_app(app)

After db.init_app, a connection pool with configured settings shall be created and bound to db when Sanic server is started, and closed on stop. Furthermore, a lazy connection context is created on each request, and released on response. That is to say, within Sanic request handlers, you can directly access db by e.g. User.get(1), everything else is settled: database pool is created on server start, connection is lazily borrowed from pool on the first database access and shared within the rest of the same request handler, and automatically returned to the pool on response.

Please be noted that, in the async world, await may block unpredictably for a long time. When this world is crossing RDBMS pools and transactions, it is a very dangerous bite for performance, even causing disasters sometimes. Therefore we recommend, during the time enjoying fast development, do pay special attention to the scope of transactions and borrowed connections, make sure that transactions are closed as soon as possible, and connections are not taken for unnecessarily long time. As for the Sanic support, if you want to release the concrete connection in the request context before response is reached, just do it like this:

await request['connection'].release()

Or if you prefer not to use the contextual lazy connection in certain handlers, prefer explicitly manage the connection lifetime, you can always borrow a new connection by setting reuse=False:

async with db.acquire(reuse=False):
    # new connection context is created

Or if you prefer not to use the builtin request-scoped lazy connection at all, you can simply turn it off:

app.config.DB_USE_CONNECTION_FOR_REQUEST = False