Hub WaitReceive uses round-robin fairness

Platform spec ADR

Hub WaitReceive uses round-robin fairness

Back to Channels and synchronization ◎ Open feature in platform map

Spec standingStandard

Owner

Piotr Mikstacki pmikstacki@cybernomad.it

Submitter

Piotr Mikstacki pmikstacki@cybernomad.it

Current document

Articles

• Channels and synchronization - Contracts and edge cases Runtime-level Send, Receive, Hub, and cancellation contracts. article Standard Reviewed Wed May 20

History

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Completeness

OKfeature · 7 SpecSection(s) · 2 H2 heading(s)

Section id	Required	Found
what-this-feature-specifies	yes	yes
implementation-anchors	yes	yes

Full tree: run pnpm verify:platform-spec-layout (writes src/generated/platform-spec-layout-report.json).

Related spec docs

• Feature
  Channels and synchronization

  Parent feature hub

• Feature
  Concurrency package

  Hub API

Context

Multiplexing without language select needs deterministic fairness when one registered channel is always ready.

Decision

Rule	Detail
Homogeneity	`Hub<T>` — homogeneous T only in v1
Scan	Cursor starts at k; scan k, k+1, … modulo registration count for first ready channel
After success	Cursor advances past chosen index (wrap)
v1 scope	WaitSend out of scope; no language select
Empty hub	WaitReceive with zero registrations → HubError::Empty

Matches D-CORE-CONC-0003.

Consequences

Runtime hub_wait_receive_* implements rotation; corelib documents registration limits for hot paths.

Verification anchors

Hub builtins; corelib hub tests.