Struct Backoff 

pub struct Backoff {
    pub initial: Duration,
    pub multiplier: f64,
    pub max: Duration,
    pub jitter: Jitter,
}

Exponential-backoff configuration.

delay(attempt) returns min(initial × multiplier^attempt, max), then applies the configured Jitter policy.

All fields are pub so you can construct + tune directly, or use one of the preset constructors (Backoff::smtp_outbound, Backoff::auth_lockout, etc.).

Fields

initial: Duration

Delay for attempt = 0.

multiplier: f64

Geometric growth factor between attempts. Common values: 2.0 (doubling) or 1.5 (gentler ramp).

max: Duration

Hard ceiling on delay — once initial × multiplier^attempt would exceed max, return max.

jitter: Jitter

Jitter policy applied to the computed delay.

Implementations

impl Backoff

pub fn new( initial: Duration, multiplier: f64, max: Duration, jitter: Jitter, ) -> Self

Construct with explicit values. Use the preset constructors below for common shapes.

pub fn smtp_outbound() -> Self

Preset for SMTP outbound delivery retries: 60s initial, 2.5× growth, 8-hour cap, Full jitter. Mirrors the legacy mailrs-outbound-queue schedule shape.

pub fn auth_lockout() -> Self

Preset for failed-auth lockout: 30min initial, 2× growth, 24-hour cap, None jitter (lockouts are deterministic by design — you want every offender to see exactly the same penalty).

pub fn webhook() -> Self

Preset for webhook delivery retries: 60s initial, 2× growth, 6-hour cap, Equal jitter. Smoother than Full jitter so subscriber endpoints see a less spiky retry pattern.

pub fn base_delay(&self, attempt: u32) -> Duration

Base delay for attempt BEFORE jitter is applied. Useful when you want to log “scheduled delay” without the random part.

pub fn delay(&self, attempt: u32, seed: u64) -> Duration

Compute the delay for attempt, applying the configured jitter. seed is a caller-supplied source of randomness — usually derived from a fresh rand::random::<u64>() or std::time::Instant::now().elapsed().as_nanos(). The crate itself has no RNG dependency.

For Jitter::None the seed is ignored. For Equal/Full it drives a deterministic mapping (same seed → same delay), so tests can be reproducible.

pub fn should_give_up(attempt: u32, max_attempts: u32) -> bool

Convenience: should this attempt give up? Returns true if attempt >= max_attempts.

Trait Implementations

impl Clone for Backoff

fn clone(&self) -> Backoff

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Backoff

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

Formats the value using the given formatter.

impl Default for Backoff

fn default() -> Self

Default: 1 second initial, 2× growth, 1 hour cap, Full jitter. Reasonable for generic HTTP/RPC retry loops; pick a preset for other use cases.

impl Copy for Backoff