Best way to decorate a view function

[mmautner]

I was investigating issue #99 about how to cache API results and realized that the Flask-Restless pre-/post-processors are not the way to go as they cannot return a response in lieu of what the class-based view functions return.

What is the best way to then go about decorating the views that get added to the app object by the Flask-Restless blueprint?

Here's a go I had it, but am curious whether there's a better/more harmonious way to do it:

#!/usr/bin/env python

import hashlib
from functools import update_wrapper
from flask import Flask
from flask import request
import flask.ext.sqlalchemy
import flask.ext.restless
from werkzeug.contrib.cache import MemcachedCache
cache = MemcachedCache(['127.0.0.1:11211'])

def get_cache(func):
    def wrapper(*args, **kwargs):
        # < 250 chars for memcached
        cache_key = hashlib.md5(request.full_path).hexdigest()
        if request.method == 'GET' and cache.get(cache_key):
            return cache.get(cache_key)

        result = func(*args, **kwargs)

        if request.method == 'GET':
            cache.set(cache_key, result)
        return result
    return update_wrapper(wrapper, func)

db = flask.ext.sqlalchemy.SQLAlchemy()

class Person(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.Unicode, unique=True)
    birth_date = db.Column(db.Date)

class Person2(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.Unicode, unique=True)
    birth_date = db.Column(db.Date)

def create_app():
    app = Flask(__name__)
    app.config['DEBUG'] = True
    app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:////tmp/test.db'
    db.init_app(app)

    db.drop_all(app=app)
    db.create_all(app=app)

    manager = flask.ext.restless.APIManager(app, flask_sqlalchemy_db=db)
    manager.create_api(Person, methods=['GET', 'POST', 'DELETE'])
    manager.create_api(Person2, methods=['GET', 'POST', 'DELETE'])

    # hackish view decoration:
    for model in [Person, Person2]:
        model_route = '{0}api0.{0}api'.format(model.__name__.lower())
        app.view_functions[model_route] = get_cache(app.view_functions[model_route])

    return app

if __name__ == "__main__":
    create_app().run(debug=True)

[jfinkels]

Would it help to allow the user to add decorator functions to the view methods (by extending the list stored at views.API.decorators)? Those decorators are applied at each request.

[chfw]

Why would a server need caching for the responses of PUT, POST and DELETE? Caching of GET response is my concern.

[jfinkels]

According to StackOverflow, if the HTTP POST request includes the appropriate headers, then the application running on the server may cache an HTTP response, whatever that may mean. I think it should be theoretically allowed even if not used often in practice. Plus it may be easier to allow a decorator on top of all methods, rather than on just one.

Perhaps Flask-Restless should provide some default caching, checking for the appropriate HTTP headers?

[chfw]

Given that I could select which HTTP method to do caching, I would support your idea of one decorator for four methods.

Internet Explorer had default caching, which took me some time to figure it out. So, personally I wouldn't want default caching unless I would like to have it.

In the example, I didn't see cache duration and cache storage. Hopefully, it's possible to use Flask-Cache.

[reubano]

...
model_route = '{0}api0.{0}api'.format(manager.collection_name(model))
...