Events are published to re-fire at a fixed interval between a start and an end time and can be unpublished. After each operation, return how many events have fired so far.

A system re-fires events on a recurring schedule. 'publish start end eventId interval' emits the event at start, start + interval, and so on, up to and including end; 'unpublish time eventId' stops a still-running event after anything due at that time has fired (the same id may be published again later). For each operation, return how many events have been fired in total from the beginning up to that operation's timestamp.