mongodb concurrency

mongo.md

def update(self, key, data):
        """ Affects only the keys in `data` """
        write = copy.copy(data)
        current = self.get(key)
        current.update(write)
        response = self.save(key, data) if current == self.get(key) else False
        # experimental
        # user should check response is not False to ensure successful update
        if not response:
            LOG.error("DB UPDATE: %s.%s | Document changed during update!",
                      self.collection_name, response)
        else:
            LOG.info("DB UPDATE: %s.%s", self.collection_name, response)
        return response