Module concurrency 

Runs at once per type or key: at most limit runs of a workflow type (or of one key of it, a tenant say) run at a time; the others wait, in the order they were started, and show as queued.

Built from runs, so a turn is kept while its run is parked and across crashes, and nothing of it touches a step:

• A start of a limited type starts a slot instead, fusee.queued/<id>, whose input names the type, ID and input.
• The slot starts the type’s (or key’s) coordinator, fusee.concurrency/<type>[/<key>], attaching to it if it runs, and asks it for a turn (a signal).
• The coordinator keeps the queue and the runs holding a turn in its journal, admits runs in the order they asked while fewer than limit hold one (a signal back), and continues as new now and then with that state.
• An admitted slot runs the workflow under its own ID as a child, gives the turn back when it ends however it ends, and returns its result.

result(id) follows the slot until the run exists (as for a delayed start). Cancelling a slot that waits takes its request back; terminate the run, not its slot, once it runs (a terminated slot keeps its turn).

Structs

Queued

A slot’s input: the run to start once admitted.

Turns

The coordinator’s state, carried across continue-as-new.

Constants

COORDINATOR_TYPE

The coordinator’s workflow type.

SLOT_TYPE

The slot’s workflow type.

Functions

coordinator_id

The coordinator’s workflow ID for a type, and a key if the limit is per key.

slot_id

The slot’s workflow ID for a run’s ID.