Struct BoundedMemoryBackend 

pub struct BoundedMemoryBackend { /* private fields */ }

A byte-weighted, sharded, in-memory RangeCacheBackend bounded to a fixed capacity, built on the standalone foyer-memory crate’s Cache – not the umbrella foyer crate (which FoyerBackend uses via HybridCache, and which transitively pulls in a disk-backed storage engine). foyer-memory is the same in-memory engine HybridCache uses internally for its RAM tier, so this reuses that eviction implementation without the disk-IO dependencies, via LfuConfig rather than FoyerBackend’s LruConfig.

Used as the shared RAM budget backing the in-process L1 cache (l1_store.rs).

Implementations

impl BoundedMemoryBackend

pub fn new(budget_bytes: usize) -> BoundedMemoryBackend

budget_bytes bounds the total weighted (byte) size of cached entries; foyer handles eviction and sharded concurrency internally.

pub fn usage(&self) -> usize

Current weighted (byte) usage, exposed for tests.

Trait Implementations

impl RangeCacheBackend for BoundedMemoryBackend

fn get<'life0, 'life1, 'async_trait>( &'life0 self, key: &'life1 str, _expected_len: u64, ) -> Pin<Box<dyn Future<Output = Option<Bytes>> + Send + 'async_trait>>

where 'life0: 'async_trait, 'life1: 'async_trait, BoundedMemoryBackend: 'async_trait,

expected_len is the exact length the caller will accept for key. A backend MUST NOT copy a value whose length differs into any faster tier it maintains (the promotion gate) and MUST treat such a value as a miss. Single-tier backends accept and ignore the parameter.

fn put<'life0, 'async_trait>( &'life0 self, key: String, value: Bytes, _hint: FillHint, ) -> Pin<Box<dyn Future<Output = ()> + Send + 'async_trait>>

where 'life0: 'async_trait, BoundedMemoryBackend: 'async_trait,

fn disk_stats(&self) -> Option<BackendDiskStats>

Disk write-path counters, for the saturation monitor’s per-second gauges. Defaulted to None so backends without a disk tier (e.g. MemoryBackend) need no override.

fn ram_usage_bytes(&self) -> Option<usize>

Accounted RAM-tier byte usage, for the saturation monitor’s residency gauge. None for backends with no RAM tier accounting (e.g. MemoryBackend). Divergence between this and process RSS is the signature of a cached value pinning more than its accounted weight.

fn ram_entries(&self) -> Option<usize>

Accounted RAM-tier entry count, the entry-count sibling to ram_usage_bytes. None for backends with no RAM tier accounting (e.g. MemoryBackend).