Module subscription 

Bounded, replayable subscription sources for RPC streams.

A SubscriptionHub holds one ring per Source. Producers append to a ring and never wait for a subscriber; each subscriber is only a cursor (the next sequence number it wants). Every ring is bounded by a frame count and a byte cap, and all rings share one process-wide byte budget: when it is exceeded, the oldest frame across all rings is evicted.

Nothing is dropped silently. A cursor that points into a gap, whether the frames were evicted or never reached the hub, reads Read::Lagged with the first missing sequence and the first one still available, and the subscriber resumes from there.

Sequence numbers start at 1 per source and are never reused within a hub. Each hub has a random SubscriptionHub::epoch; a new hub (a daemon restart or reload) starts numbering again, so a client resumes with the epoch and since_seq it last saw, and a different epoch is reported as a break in continuity rather than matched by number.

Structs

RingLimits

Per-ring caps.

SubscriptionHub

The process’s subscription sources. Cheap to share behind an Arc.

Enums

Read

What a cursor reads.

Source

A subscribable stream.

Constants

DEFAULT_BYTE_BUDGET

Default process-wide byte budget across every ring.

DEFAULT_RING_LIMITS

Default per-source ring caps.

READ_BATCH

Frames a subscriber reads per wakeup before yielding.