Struct DefaultLease 

pub struct DefaultLease { /* private fields */ }

Default lease implementation with single-index lock-free architecture.

Performance Characteristics

• is_expired(): O(1), ~10-20ns, lock-free
• register(): O(1), ~20ns, lock-free (single shard write lock)
• unregister(): O(1), ~20ns, lock-free (single shard write lock)
• cleanup(): O(N), time-limited, shard read locks (rare: 1/1000 applies)

Memory Usage

• Per-key overhead: ~50 bytes (single DashMap entry)
• Expired keys are removed automatically during cleanup

Implementations

impl DefaultLease

pub fn new(config: LeaseConfig) -> DefaultLease

Creates a new default lease manager with the given configuration.

Arguments

• config - Lease cleanup strategy configuration

pub fn get_expiration(&self, key: &[u8]) -> Option<SystemTime>

Get expiration time for a specific key.

Performance

O(1) - DashMap lookup, lock-free

pub fn from_snapshot(data: &[u8], config: LeaseConfig) -> DefaultLease

Restore from snapshot data (used during initialization).

Filters out already-expired keys during restoration.

Arguments

• data - Serialized snapshot data
• config - Lease configuration to use

pub fn config(&self) -> &LeaseConfig

Returns reference to the lease configuration.

Used by StateMachine implementations to check cleanup strategy.

Trait Implementations

impl Debug for DefaultLease

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

Formats the value using the given formatter.

impl Lease for DefaultLease

fn register(&self, key: Bytes, ttl_secs: u64)

Register a key with TTL (Time-To-Live).

TTL Semantics

• Absolute expiration time: The expiration time is calculated as expire_at = SystemTime::now() + Duration::from_secs(ttl_secs) and stored internally.
• Crash-safe: The absolute expiration time survives node restarts. After crash recovery, expired keys remain expired (no TTL reset).
• Persistent: The expiration time is persisted to disk during snapshot generation and graceful shutdown.

Example

T0:  register(key="foo", ttl=10) → expire_at = T0 + 10 = T10
T5:  CRASH
T12: RESTART
     → WAL replay: expire_at = T10 < T12 (already expired)
     → Key is NOT restored (correctly expired)

Arguments

• key - The key to register expiration for
• ttl_secs - Time-to-live in seconds from now

Performance

O(1) - Completely lock-free, only acquires single shard write lock

fn unregister(&self, key: &[u8])

Unregister a key’s TTL.

Performance

O(1) - Completely lock-free, only acquires single shard write lock

fn is_expired(&self, key: &[u8]) -> bool

Check if a key has expired.

Performance

O(1) - Lock-free DashMap lookup

fn get_expired_keys(&self, now: SystemTime) -> Vec<Bytes>

Get all expired keys (without time limit).

This method is rarely used directly. Most cleanup happens via on_apply().

Performance

O(N) - Iterates all keys with shard read locks

fn on_apply(&self) -> Vec<Bytes>

Piggyback cleanup on apply operations (DEPRECATED - no longer used).

This method is kept for backward compatibility but is no longer called. Cleanup is now handled by:

• Lazy strategy: cleanup in get() method
• Background strategy: dedicated async task

Performance

• Fast path: O(1) - always returns empty vec

fn has_lease_keys(&self) -> bool

Check if any keys have been registered.

Performance

O(1) - Single atomic load

fn may_have_expired_keys(&self, now: SystemTime) -> bool

Quick check if there might be expired keys.

This is a heuristic check - samples first 10 entries. May return false negatives but never false positives.

Performance

O(1) - Checks first few entries only

fn len(&self) -> usize

Get total number of keys with active leases.

Performance

O(1) - DashMap maintains internal count

fn to_snapshot(&self) -> Vec<u8>

Serialize current lease state to snapshot.

Performance

O(N) - Iterates all keys with shard read locks

fn reload(&self, data: &[u8]) -> Result<(), Error>

Reload lease state from snapshot.

Filters out already-expired keys during restoration.

Performance

O(N) - Rebuilds single index

fn is_empty(&self) -> bool

Check if no keys have active leases.