storage.py 文件源码

def _bump_timestamp(self, collection_id, parent_id, record=None,
                        modified_field=None, last_modified=None):

        key = '{0}.{1}.timestamp'.format(collection_id, parent_id)
        while 1:
            with self._client.pipeline() as pipe:
                try:
                    pipe.watch(key)
                    previous = pipe.get(key)
                    pipe.multi()
                    # XXX factorize code from memory and redis backends.
                    is_specified = (record is not None and
                                    modified_field in record or
                                    last_modified is not None)
                    if is_specified:
                        # If there is a timestamp in the new record,
                        # try to use it.
                        if last_modified is not None:
                            current = last_modified
                        else:
                            current = record[modified_field]
                    else:
                        current = utils.msec_time()

                    if previous and int(previous) >= current:
                        collection_timestamp = int(previous) + 1
                    else:
                        collection_timestamp = current

                    # Return the newly generated timestamp as the current one
                    # only if nothing else was specified.
                    is_equal = previous and int(previous) == current
                    if not is_specified or is_equal:
                        current = collection_timestamp

                    pipe.set(key, collection_timestamp)
                    pipe.execute()
                    return current
                except redis.WatchError:  # pragma: no cover
                    # Our timestamp has been modified by someone else, let's
                    # retry.
                    # XXX: untested.
                    continue