a safe datastore model for google appengine

gistfile1.py

import logging
import time

from google.appengine.runtime import apiproxy_errors
from google.appengine.ext import db

DATASTORE_NB_RETRY=5
DATASTORE_TIME_RETRY=.15
DATASTORE_DEFAULT_DEADLINE=5
DATASTORE_DEFAULT_CFG=db.create_config(
    deadline=DATASTORE_DEFAULT_DEADLINE)


def _cfg_kwargs(**kw):
    if not kw.has_key('config'):
        kw['config'] = CFG_DEADLINE
    return kw

class SafeModel(db.Model):
    def put(self, **kw):
        kw = _cfg_kwargs(**kw)
        for retry in range(DATASTORE_NB_RETRY):
            try:
                return super(db.Model, self).put(**kw)
            except(db.Timeout, 
                   db.TransactionFailedError,
                   apiproxy_errors.ApplicationError,
                   apiproxy_errors.DeadlineExceededError), e:
                logging.warn("Error during the put process, "
        	             "retry %d in %.2fs", retry, DATASTORE_TIME_RETRY)
                logging.debug(e.message)
                time.sleep(DATASTORE_TIME_RETRY)
        logging.exception(e)

    def delete(self, **kw):
        kw = _cfg_kwargs(**kw)
        for retry in range(DATASTORE_NB_RETRY):
            try:
                return super(db.Model, self).delete(**kw)
            except(db.Timeout,
                   apiproxy_errors.ApplicationError,
                   apiproxy_errors.DeadlineExceededError), e:
                logging.warn("Error during the delete process, "
                             "retry %d in %.2fs", retry, DATASTORE_TIME_RETRY)
                logging.debug(e.message)
                time.sleep(DATASTORE_TIME_RETRY)
        logging.exception(e)

    @classmethod
    def get_by_key_name(cls, key_names, parent=None, **kw):
        kw = _cfg_kwargs(**kw)
        for retry in range(DATASTORE_NB_RETRY):
            try:
                return super(db.Model, cls).get_by_key_name(key_names, parent=parent, **kw)
            except(db.Timeout, 
                   apiproxy_errors.ApplicationError,
                   apiproxy_errors.DeadlineExceededError), e:
                logging.warn("Error during the get_by_key_name"
                             "process, retry %d in %.2fs", retry, DATASTORE_TIME_RETRY)
                logging.debug(e.message)
                time.sleep(DATASTORE_TIME_RETRY)
        logging.exception(e)