public static interface Backlogs.HasPartitionedBacklog extends Backlogs.HasBacklog
RestrictionTrackers which can provide a backlog that is from a shared resource such as a message queue should implement this interface to provide the partition identifier. The partition identifier is used by runners for various backlog calculations. Backlogs reported with the same partition identifier represent a point in time reporting of the backlog for that partition. For example, a runner can compute a global backlog by summing all reported backlogs over all unique partition identifiers.
For example SplittableDoFn's which consume elements from:
RestrictionTrackers is to use the encoded element and restriction pair.
Returns an immutable representation of the partition identifier.