Instrumentation through descriptors

descriptor_test.py

from pprint import pprint as ppr
from collections import defaultdict
from datetime import datetime as dt


class Db(object):

    def default_obj(self):
        return dict(
            last_modified=None,
            current=None,
            values=[],
            accessed=0,
        )

    def __init__(self, url):
        self.host = url
        self.db = defaultdict(self.default_obj)

    def read(self, k):
        self.db[k]['accessed'] += 1

    def write(self, k, v):
        self.db[k]['values'].append(v)
        self.db[k]['current'] = v
        self.db[k]['last_modified'] = dt.now()

    @property
    def data(self):
        return self.db


def configure(db):
    """Configure the instrumented descriptor with some values."""
    class Instrumented(object):

        def __init__(self, name, val):
            self.name = name
            self.val = val
            self.db = db

        def __get__(self, obj, objtype):
            self.db.read(self.name)
            return self.val

        def __set__(self, obj, val):
            self.db.write(self.name, self.val)
            self.val = val

    return Instrumented


mydb = Db('https://MY.SWEET.DATASTORE.com:8091')
InstrumentedField = configure(mydb)


class MyClass(object):
    field1 = InstrumentedField('field-1', 1)
    field2 = InstrumentedField('field-2', 'radSauce')


cls1 = MyClass()

# Demonstrating accessing the var writes to a "db"
map(lambda x: cls1.field1, range(10))
cls1.field1 = 'Boom'
cls1.field2

ppr(mydb.data)