kojin_core/
backoff.rs

1use serde::{Deserialize, Serialize};
2use std::time::Duration;
3
4/// Strategy for calculating retry backoff delays.
5#[derive(Debug, Clone, Serialize, Deserialize)]
6#[serde(tag = "type", rename_all = "snake_case")]
7pub enum BackoffStrategy {
8    /// Fixed delay between retries.
9    Fixed { delay_secs: u64 },
10    /// Exponential backoff: base_secs * 2^retry, capped at max_secs.
11    Exponential { base_secs: u64, max_secs: u64 },
12}
13
14impl BackoffStrategy {
15    /// Calculate the delay for the given retry attempt (0-indexed).
16    pub fn delay_for(&self, retry: u32) -> Duration {
17        match self {
18            BackoffStrategy::Fixed { delay_secs } => Duration::from_secs(*delay_secs),
19            BackoffStrategy::Exponential {
20                base_secs,
21                max_secs,
22            } => {
23                let exp = 1u64.checked_shl(retry).unwrap_or(u64::MAX);
24                let delay = base_secs.saturating_mul(exp);
25                Duration::from_secs(delay.min(*max_secs))
26            }
27        }
28    }
29}
30
31impl Default for BackoffStrategy {
32    fn default() -> Self {
33        BackoffStrategy::Exponential {
34            base_secs: 1,
35            max_secs: 300,
36        }
37    }
38}
39
40#[cfg(test)]
41mod tests {
42    use super::*;
43
44    #[test]
45    fn fixed_backoff() {
46        let strategy = BackoffStrategy::Fixed { delay_secs: 5 };
47        assert_eq!(strategy.delay_for(0), Duration::from_secs(5));
48        assert_eq!(strategy.delay_for(1), Duration::from_secs(5));
49        assert_eq!(strategy.delay_for(10), Duration::from_secs(5));
50    }
51
52    #[test]
53    fn exponential_backoff() {
54        let strategy = BackoffStrategy::Exponential {
55            base_secs: 1,
56            max_secs: 60,
57        };
58        assert_eq!(strategy.delay_for(0), Duration::from_secs(1));
59        assert_eq!(strategy.delay_for(1), Duration::from_secs(2));
60        assert_eq!(strategy.delay_for(2), Duration::from_secs(4));
61        assert_eq!(strategy.delay_for(3), Duration::from_secs(8));
62        // Should cap at max_secs
63        assert_eq!(strategy.delay_for(10), Duration::from_secs(60));
64    }
65
66    #[test]
67    fn exponential_backoff_overflow() {
68        let strategy = BackoffStrategy::Exponential {
69            base_secs: 1,
70            max_secs: 300,
71        };
72        // Very high retry count should not panic
73        assert_eq!(strategy.delay_for(100), Duration::from_secs(300));
74    }
75
76    #[test]
77    fn backoff_serde_roundtrip() {
78        let strategy = BackoffStrategy::Exponential {
79            base_secs: 2,
80            max_secs: 120,
81        };
82        let json = serde_json::to_string(&strategy).unwrap();
83        let deserialized: BackoffStrategy = serde_json::from_str(&json).unwrap();
84        assert_eq!(strategy.delay_for(3), deserialized.delay_for(3));
85    }
86}
kojin_core/backoff.rs

kojin_core/
backoff.rs
