Snapshottable counters.
Periodically emits deltas based off a Counters object.
Use this when too lazy to create a domain-specific Counters class.
Use this when too lazy to create a domain-specific Counters class. Uses memory linear in the number of keys ever seen.
Snapshottable counters. Useful for both streaming metrics (snapshot periodically, emit) and batch metrics (snapshot once at the end of a task).