Trait MemoryConsumer 

pub trait MemoryConsumer: Send + Sync {
    // Required methods
    fn name(&self) -> &str;
    fn memory_usage(&self) -> usize;
    fn eviction_priority(&self) -> u8;
    fn region(&self) -> MemoryRegion;
    fn evict(&self, target_bytes: usize) -> usize;
    fn current_tier(&self) -> StorageTier;

    // Provided methods
    fn can_spill(&self) -> bool { ... }
    fn spill(&self, _target_bytes: usize) -> Result<usize, SpillError> { ... }
    fn reload(&self) -> Result<(), SpillError> { ... }
}

Trait for subsystems that consume managed memory.

Memory consumers register with the buffer manager and participate in eviction when memory pressure is detected. Lower priority consumers are evicted first.

Required Methods

fn name(&self) -> &str

Returns a unique name for this consumer (for debugging/logging).

fn memory_usage(&self) -> usize

Returns current memory usage in bytes.

fn eviction_priority(&self) -> u8

Returns eviction priority (0 = lowest priority, evict first; 255 = highest, evict last).

fn region(&self) -> MemoryRegion

Returns which memory region this consumer belongs to.

fn evict(&self, target_bytes: usize) -> usize

Attempts to evict/release memory to reach target usage.

Returns the number of bytes actually freed.

fn current_tier(&self) -> StorageTier

Reports the consumer’s current storage tier (Phase 8b introspection).

No default: tier cannot be inferred from memory_usage() alone because a spillable consumer can be on disk with zero heap usage, and crate::memory::buffer::BufferManager::reload_eligible only reloads consumers reporting StorageTier::OnDisk. Implementors that never spill should return StorageTier::InMemory when memory_usage() > 0 and StorageTier::Uninitialized otherwise.

Used by crate::memory::buffer::BufferManager::snapshot_consumer_tiers for observability and tests; not on any hot path.

Provided Methods

fn can_spill(&self) -> bool

Returns whether this consumer supports spilling to disk.

fn spill(&self, _target_bytes: usize) -> Result<usize, SpillError>

Spills data to disk to free memory.

Returns the number of bytes freed on success.

Errors

Returns an error if spilling fails or is not supported.

fn reload(&self) -> Result<(), SpillError>

Reloads spilled data from disk (called when memory becomes available).

Errors

Returns an error if reloading fails.

Implementors