Struct PhiAccrualState 

pub struct PhiAccrualState {
    pub inter_arrival_history: VecDeque<u64>,
    pub history_capacity: usize,
    pub threshold_phi: f64,
    pub down_phi: f64,
}

φ-accrual failure detector per direct chain neighbor. Heartbeat = any wire round-trip in the last window; rising φ indicates the peer is silent relative to its historical inter-arrival distribution.

Implementation per Hayashibara et al. - exponential approximation of the empirical inter-arrival distribution. The threshold defaults to 8 (Cassandra / Akka conservative).

Fields

inter_arrival_history: VecDeque<u64>

Recent inter-arrival times of heartbeats, nanoseconds.

VecDeque so eviction at capacity is O(1) pop_front instead of O(n) Vec::remove(0) memmove. At history_capacity = 1000 and per-heartbeat ingest, the quadratic cost dominated when φ-accrual ran on dozens of peers in steady state.

history_capacity: usize

Capacity of the rolling history.

threshold_phi: f64

Suspicion threshold; φ > this → peer is suspect.

down_phi: f64

Hard-down threshold; φ > this → peer is down.

Implementations

impl PhiAccrualState

pub fn record_heartbeat(&mut self, now_ns: u64, last_seen_at_ns: u64)

Record a heartbeat at now_ns given the prior heartbeat at last_seen_at_ns. The inter-arrival time enters the rolling history (oldest sample evicted at capacity).

pub fn phi(&self, now_ns: u64, last_seen_at_ns: u64) -> f64

Compute current suspicion level φ. Returns 0.0 when no history is available (i.e., no heartbeats yet - the peer is assumed alive on the first contact).

pub fn is_suspect(&self, now_ns: u64, last_seen_at_ns: u64) -> bool

true once φ crosses Self::threshold_phi.

pub fn is_down(&self, now_ns: u64, last_seen_at_ns: u64) -> bool

true once φ crosses Self::down_phi (hard fail).

Trait Implementations

impl Clone for PhiAccrualState

fn clone(&self) -> PhiAccrualState

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for PhiAccrualState

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

Formats the value using the given formatter.

impl Default for PhiAccrualState

fn default() -> Self

Returns the “default value” for a type.