Timer

One schedule of an aggregate: send the command of type commandType, body its JSON, to target each time rule says, the next time dueAt (epoch milliseconds), for its slot, due at slotDueAt.

• id is ref#key@version, its names escaped, the schedule as the owner's stream at version set it (Timers.idOf); the command of each slot is sent with the request id id#slot (requestId), so sending it again is deduplicated by its target.

• owner and key name the schedule: the aggregate that set it (Timers.ownerOf), compared field by field, never by its joined name, so two aggregates whose tenant and id join alike keep their timers apart; version orders the owner's changes (TimerStore).

• slot counts the times the schedule is due, from 1: firing a slot marks it fired and moves dueAt to the next one in one write; a rule due once has one slot, after which the timer is FIRED. A recurring rule's slot is the number of its times since it was set, so slots it skipped (missed and coalesced, me.ahoo.wow.api.schedule.Misfire) are counted too: skipped is how many slots before this one were not sent.

• slotDueAt is when the current slot is due, as its rule said; dueAt is when the firing loop next looks at the timer: the slot's due time at first, then the claim's deadline while it is sent, or the next attempt after a technical failure. Every send of the slot, retried or claimed anew, carries slotDueAt (context), so its target never decides it before then; it moves only with the slot.

• partition is the partition of the owner among its context's log partitions: the owner of that partition writes the timer from the owner's events and fires it, and a sharded store shards the timers by it, so the due read and every read or write by owner reach one shard. The command reaches a target owned elsewhere through the cluster channel.

• causation links the command to the commit that set the schedule; headers and operator are the setting command's, which the command inherits, and scope the setting commit's, the owner and space the command is sent in.

• status, attempts and outcome record what the firing loop did: outcome is what the target answered (TimerOutcomes), or why a timer is parked.

Fields may be added: construct one with of; the constructor is internal to Wow.