Struct Timing 

pub struct Timing {
    pub heartbeat_ms: u64,
    pub election_ms: u64,
}

Failure detection, in milliseconds of each member’s monotonic clock.

An idle primary sends a heartbeat every heartbeat_ms. A backup that hears nothing from its primary for election_ms, plus a jitter drawn again for every election from 0..election_ms, starts a view change, so the loss of a primary is noticed within one to two election timeouts.

Fields

heartbeat_ms: u64

election_ms: u64

Implementations

impl Timing

pub fn validate(&self) -> Result<(), &'static str>

A heartbeat of at least 1 ms and an election timeout of at least four heartbeats, so a backup can miss a few before it suspects the primary.

pub fn promise_ms(&self) -> u64

How long a backup promises, after each ping from its primary, not to take part in a view change: half the election timeout, so an election that times out normally never breaks a promise.

pub fn lease_ms(&self) -> u64

How long after it sent a ping that a quorum answered the primary may serve reads from its own state. The promise as the slowest allowed backup clock measures it, as the fastest allowed primary clock measures it, less a millisecond at each end for clock granularity: (P - 1)(1 - ρ)/(1 + ρ) - 1 with ρ = MAX_CLOCK_DRIFT_PPM.

pub fn step_down_ms(&self) -> u64

How long a primary that hears from no quorum keeps its role: four election timeouts, and at least 200 ms. A backup that is merely slow (a stalled flush, a starting process) answers late; one that lost this primary has elected another long before.

Trait Implementations

impl Clone for Timing

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Timing

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

Formats the value using the given formatter.

impl Default for Timing

fn default() -> Self

Returns the “default value” for a type.