Closes closer.

MakeRootLoggerWithContext creates a base logger by wrapping a commontypes.Logger.

MergeOverwrite will create a new LogFields and add all the properties from upserts on it.

MergePreserve will create a new LogFields and add all the properties from extras on it.

If Stop is called prior to expiry of d, f won't be executed.

LogarithmicTaper provides logarithmic tapering of an event sequence.