Struct ObjectStorageTiering 

pub struct ObjectStorageTiering { /* private fields */ }

Production-quality hierarchical object storage tiering engine.

Maintains a set of TieredObject instances distributed across Hot, Warm, and Cold tiers. Automatic promotion/demotion is driven by the OstTierPolicy supplied in OstTierConfig.

Implementations

impl ObjectStorageTiering

pub fn new(config: OstTierConfig) -> Self

Create a new tiering engine with the supplied configuration.

pub fn store( &mut self, object: TieredObject, ) -> Result<OstStorageTier, TieringError>

Store an object, placing it in the most appropriate tier based on policy and available capacity.

New objects always attempt Hot first, then Warm, then Cold. The current_tier field of the supplied object is ignored; the actual assigned tier is returned.

Returns TieringError::TierFull if no tier can accept the object.

pub fn retrieve( &mut self, id: &str, current_ts: u64, ) -> Result<&TieredObject, TieringError>

Retrieve an object by ID, updating its last_accessed timestamp and incrementing access_count. If the access count crosses the configured promotion threshold the object is queued for promotion.

Returns TieringError::ObjectNotFound if the ID is unknown.

pub fn promote( &mut self, id: &str, to: OstStorageTier, current_ts: u64, ) -> Result<OstTierTransition, TieringError>

Promote an object to a hotter tier.

Returns TieringError::TierFull if the target tier lacks capacity. Returns TieringError::ObjectNotFound if the ID is unknown. Returns TieringError::PolicyConflict if to is colder than or equal to the object’s current tier (use demote instead).

pub fn demote( &mut self, id: &str, to: OstStorageTier, current_ts: u64, ) -> Result<OstTierTransition, TieringError>

Demote an object to a colder tier.

Returns TieringError::TierFull if the target tier lacks capacity. Returns TieringError::ObjectNotFound if the ID is unknown. Returns TieringError::PolicyConflict if to is hotter than or equal to the object’s current tier.

pub fn run_policy(&mut self, current_ts: u64) -> Vec<OstTierTransition>

Evaluate all objects against the active policy and perform automatic promotions and demotions. Returns all transitions that occurred.

Policies applied:

• AccessFrequency(n): objects with access_count > n not in Hot → promote.
• RecencyBased(window_us): objects not accessed in window_us µs → Cold.
• SizeThreshold: enforce per-tier byte caps by demoting largest objects first.
• CostOptimized(multiplier): demote objects whose cost-adjusted score ranks them as low-value, keeping total cost under budget.
• ManualOnly: no automatic transitions.

pub fn evict_tier( &mut self, tier: OstStorageTier, needed_bytes: u64, ) -> Vec<OstTierTransition>

Demote objects from tier to make room for needed_bytes, using Least-Recently-Used ordering. Returns all transitions performed.

Objects are demoted one tier at a time (Hot→Warm or Warm→Cold).

pub fn evict_tier_ts( &mut self, tier: OstStorageTier, needed_bytes: u64, current_ts: u64, ) -> Vec<OstTierTransition>

Like evict_tier but accepts an explicit timestamp.

pub fn tier_objects(&self, tier: OstStorageTier) -> Vec<&TieredObject>

Return references to all objects currently in tier.

pub fn transition_history(&self) -> Vec<OstTierTransition>

Return a copy of the last up-to-500 tier transitions (oldest first).

pub fn stats(&self) -> TieringStats

Return aggregate statistics for all tiers.