Struct Budget 

pub struct Budget { /* private fields */ }

A memory budget for a single engine.

Tracks current allocation against a configurable limit using atomic counters (safe to read from any thread — metrics exporter, governor, etc.).

The allocated counter is stored behind an Arc so that ReservationToken can hold a reference to it without requiring a back-reference to the governor.

Implementations

impl Budget

pub fn new(limit: usize) -> Self

Create a new budget with the given limit.

pub fn try_reserve(&self, size: usize) -> bool

Try to reserve size bytes from this budget.

Returns true if the reservation succeeded, false if it would exceed the limit.

pub fn try_reserve_arc(&self, size: usize) -> Option<Arc<AtomicUsize>>

Try to reserve size bytes and return a shared Arc to the allocated counter so the caller can decrement it on drop.

Returns Some(arc) on success, None on budget exhaustion.

pub fn release(&self, size: usize)

Release size bytes back to the budget.

Saturates to zero if size exceeds the current allocation (which can happen when data is replayed from WAL without a matching reservation).

pub fn allocated(&self) -> usize

Current allocated bytes.

pub fn limit(&self) -> usize

Hard limit in bytes.

pub fn over_release_count(&self) -> usize

Number of over-release events observed on this budget. A non-zero value is the smoking-gun signal that some call-site is releasing more bytes than it reserved. Per-engine allocated() saturates to zero on over-release, so this counter is the only post-hoc observable.

pub fn available(&self) -> usize

Remaining bytes available.

pub fn utilization_percent(&self) -> u8

Utilization as a percentage (0-100).

Computed in u128 so a corrupted (e.g. underflow-wrapped near usize::MAX) allocated clamps to 100 % rather than panicking on allocated * 100 overflow — a panic here is taken inside the Data Plane core loop (apply_spsc_pressure → snapshot) and escalates to a DEGRADED core.

pub fn peak(&self) -> usize

Peak allocation (high-water mark).

pub fn rejections(&self) -> usize

Number of rejected allocation attempts.

pub fn set_limit(&self, new_limit: usize)

Update the limit dynamically (for rebalancing).

The new limit must be >= current allocation. If it’s less, the limit is set to the current allocation (no immediate eviction).

Trait Implementations

impl Debug for Budget

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

Formats the value using the given formatter.