use std::time::Duration;
use rand::Rng;
pub(crate) fn is_retryable_status(status: u16) -> bool {
matches!(status, 429 | 500 | 502 | 503 | 504)
}
pub(crate) fn retry_backoff_delay(attempt: u32) -> Duration {
let base_ms: u64 = 1000u64.saturating_mul(2u64.saturating_pow(attempt));
let jitter_range = base_ms / 4; let jitter = if jitter_range > 0 {
let offset = rand::thread_rng().gen_range(0..=jitter_range * 2);
offset as i64 - jitter_range as i64
} else {
0
};
let delay_ms = (base_ms as i64 + jitter).max(100) as u64;
Duration::from_millis(delay_ms)
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_is_retryable_status() {
assert!(is_retryable_status(429));
assert!(is_retryable_status(500));
assert!(is_retryable_status(502));
assert!(is_retryable_status(503));
assert!(is_retryable_status(504));
assert!(!is_retryable_status(400));
assert!(!is_retryable_status(401));
assert!(!is_retryable_status(403));
assert!(!is_retryable_status(404));
assert!(!is_retryable_status(422));
assert!(!is_retryable_status(200));
assert!(!is_retryable_status(201));
}
#[test]
fn test_retry_backoff_delay_exponential_growth() {
for _ in 0..20 {
let d0 = retry_backoff_delay(0);
let d1 = retry_backoff_delay(1);
let d2 = retry_backoff_delay(2);
assert!(d0.as_millis() >= 750, "attempt 0 too low: {:?}", d0);
assert!(d0.as_millis() <= 1250, "attempt 0 too high: {:?}", d0);
assert!(d1.as_millis() >= 1500, "attempt 1 too low: {:?}", d1);
assert!(d1.as_millis() <= 2500, "attempt 1 too high: {:?}", d1);
assert!(d2.as_millis() >= 3000, "attempt 2 too low: {:?}", d2);
assert!(d2.as_millis() <= 5000, "attempt 2 too high: {:?}", d2);
}
}
#[test]
fn test_retry_backoff_delay_minimum() {
for _ in 0..20 {
let delay = retry_backoff_delay(0);
assert!(delay.as_millis() >= 100);
}
}
#[test]
fn test_retry_backoff_delay_no_overflow() {
let delay = retry_backoff_delay(30);
assert!(delay.as_millis() >= 100);
}
}