Struct TrunkConfig 

#[non_exhaustive]
pub struct TrunkConfig {
    pub timed_capacity: NonZeroUsize,
    pub sparse_capacity: NonZeroUsize,
    pub segment_capacity: NonZeroUsize,
    pub event_capacity: NonZeroUsize,
    pub part_capacity: NonZeroUsize,
}

Available on crate feature std only.

Construction parameters for a Trunk.

Why every capacity is a NonZeroUsize, not a validated usize

A zero capacity is not a value this type rejects — it is a value this type cannot represent. Every ring in this module evicts its oldest entry when entries.len() == capacity, so a zero capacity would evict every entry the instant it was pushed, and a zero waiter cap would make Trunk::listen incapable of ever registering anybody: not a configuration, a broken one.

Two weaker designs were considered and rejected:

• Panicking on zero in Trunk::new (what this type did before): internally consistent, but a library that panics on a value which arrives from a file is a real operational hazard, not a style question — multimux takes its routes from a JSON config, so once these capacities become operator-configurable a stray 0 would take down the server process instead of producing a config error. It also contradicted transmux::ProgressiveDemux::new’s deliberate panic-to-fallible change, which is exactly the kind of two-crates-apart inconsistency that makes an API feel arbitrary.
• A fallible TrunkConfig::new -> Result<Self, _> (the ProgressiveDemux shape): correct, but strictly worse here. ProgressiveDemux already returns Result as part of its Stage contract and already has an Error type; TrunkConfig has neither, so this would mean inventing a construction error type and threading ?/unwrap through every construction site to encode one bit of information the type system can carry for free. NonZeroUsize puts the invariant in the signature, where a reader learns it without reading this doc — and, for the JSON-config hazard specifically, a serde deserialize of 0 into a NonZeroUsize field already fails as an ordinary deserialization error at the config boundary, with no hand-written check and no panic.

Fields (Non-exhaustive)

Non-exhaustive structs could have additional fields added in future. Therefore, non-exhaustive structs cannot be constructed in external crates using the traditional Struct { .. } syntax; cannot be matched against without a wildcard ..; and struct update syntax will not work.

timed_capacity: NonZeroUsize

Bound, in entry count, on the RetentionClass::Timed ring.

sparse_capacity: NonZeroUsize

Bound, in entry count, on the RetentionClass::Sparse ring — independent of timed_capacity; see RetentionClass::Sparse for why that independence is the entire point of the retention rule.

segment_capacity: NonZeroUsize

Bound, in entry count, on the segment log. Also the bound a pinning SegmentCursor’s retention is measured against — see The DVR contradiction for why there is deliberately no second, independent “pin depth” knob.

event_capacity: NonZeroUsize

Bound, in entry count, on the event log — and on its segment boundary table (EventLog::segment_starts). See The event log for why a segment-relative event’s target boundary shares this one knob rather than getting a second, independently-tuned one — exactly TrunkConfig::segment_capacity’s “no second capacity knob” precedent for pinning.

part_capacity: NonZeroUsize

Bound, in entry count, on the live-part log (step 3b-iv) — and on how many concurrent Trunk::listen registrations this trunk will honor at once. See The live-part log for why a part-of-the-open-segment shares this one knob for both jobs, rather than getting a second, independently-tuned “how many waiters” setting — the third instance of this file’s “no second capacity knob” precedent (after TrunkConfig::segment_capacity’s pin reuse and TrunkConfig::event_capacity’s segment_starts reuse).

Implementations

impl TrunkConfig

pub fn new( timed_capacity: NonZeroUsize, sparse_capacity: NonZeroUsize, segment_capacity: NonZeroUsize, event_capacity: NonZeroUsize, part_capacity: NonZeroUsize, ) -> Self

Build a config with all five ring capacities. Nothing is validated here, and nothing needs to be: NonZeroUsize makes the only invalid value unrepresentable rather than merely rejected — see this type’s own docs for why that beats both the panic this replaced and a fallible constructor.

Trait Implementations

impl Clone for TrunkConfig

fn clone(&self) -> TrunkConfig

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for TrunkConfig

impl Debug for TrunkConfig

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.