Module runtime 

Runtime primitives for bounded back-pressure.

The dispatcher and other internal pipelines need to refuse work fast when downstream stages cannot keep up, rather than buffer requests indefinitely and grow process memory without bound. This module provides two complementary tools, modelled after the building blocks used by the Riak Core stack:

• Sidejob wraps a per-stage worker actor with a fixed-size tokio mailbox. Submissions to a full mailbox return SidejobError::Overloaded immediately so the caller can fail fast (the moral equivalent of a 503).
• Throttle is a token-bucket admission control gate. Internal queues call Throttle::try_acquire to fast-fail or Throttle::acquire to wait for tokens to refill at a configured rate.

Both tools register Prometheus metric families against the default process-wide registry the first time they are constructed:

• sidejob_overload_total{name="..."} - counter, incremented every time a submit is rejected because the mailbox is full.
• throttle_wait_seconds{queue="..."} - histogram (1 ms .. 10 s), recording the time a caller waited inside Throttle::acquire before tokens became available.

Structs

Sidejob

Handle to a sidejob actor.

Throttle

Token-bucket admission control gate.

Enums

SidejobError

Reasons a submit may fail.

ThrottleError

Errors returned by Throttle::acquire_blocking.