Optional: Library of Examples

How-To's and Code Examples¶

Heaven is currently being used in production by a few customer facing web products and to power high performance microservices. Below are some of the observations and collated practices that might help provide some guidance on code patterns possible in heaven.

Decorator Functions¶

Useful for intercepting and performing actions before the decorated function is invoked i.e. authentication, dependency injection, or authorization amongst other possibilities.

This example demonstrates one of the ways Authentication might be implemented with the pyjwt library.

from asyncpg import Pool
from jwt import decode


def protected(func):
    """Authentication"""
    @wraps(func)
    def delegate(r: Request, w: Response, c: Context):
        token = r.headers.get('authorization')
        secret_key = r.app.CONFIG('SECRET_KEY')

        try: credentials = decode(token, secret_key, algorithm='HS256')
        except: return w.status = status.UNAUTHORIZED
        else: c.keep('current_user') = credentials.get('id')

        return await func(r, w, c)
    return delegate


def private(resource: str):
    """RBAC Authorization, heaven makes it easy to also use ABAC"""
    def wrapper(func):
        @wraps(func)
        def delegate(r: Request, w: Response, c: Context):
            dbpool: Pool = r.app.peek('dbpool')
            action = r.method.lower()
            with dbpool.acquire() as sqld:
                try: roles = await sqld.fetchval("""
                    SELECT roles
                    FROM privileges
                    WHERE user = $1 AND action = $2 AND resource = $3
                """, c.current_user, action, resource)
                except:
                    w.status = HTTPStatus.SERVICE_UNAVAILABLE
                    w.body = dumps({'message': 'please try again later'})
            if action in roles: return await func(r, w, c)

            w.status = HTTPStatus.UNAUTHORIZED
            w.body = dumps({'message': 'insufficient privileges'})
        return delegate
    return wrapper