firebase_rs_sdk/storage/request/
backoff.rs

1use rand::Rng;
2use std::time::{Duration, Instant};
3
4/// Configuration for exponential backoff when issuing storage requests.
5#[derive(Clone, Debug)]
6pub struct BackoffConfig {
7    /// Initial delay applied before the second attempt.
8    pub initial_delay: Duration,
9    /// Maximum delay between attempts.
10    pub max_delay: Duration,
11    /// Total time budget for the request, including all retries.
12    pub total_timeout: Duration,
13    /// Maximum number of attempts before giving up.
14    pub max_attempts: usize,
15}
16
17impl BackoffConfig {
18    /// Creates a configuration using Storage defaults (1s base, up to 64s, 2m timeout).
19    pub fn standard_operation() -> Self {
20        Self {
21            initial_delay: Duration::from_secs(1),
22            max_delay: Duration::from_secs(64),
23            total_timeout: Duration::from_secs(2 * 60),
24            max_attempts: 8,
25        }
26    }
27
28    /// Configuration tuned for long running uploads (same defaults as the JS SDK).
29    pub fn upload_operation(max_retry_time: Duration) -> Self {
30        Self {
31            total_timeout: max_retry_time,
32            ..Self::standard_operation()
33        }
34    }
35
36    pub fn with_total_timeout(mut self, timeout: Duration) -> Self {
37        self.total_timeout = timeout;
38        self
39    }
40}
41
42/// Tracks the evolving backoff state across attempts.
43#[derive(Debug)]
44pub struct BackoffState {
45    config: BackoffConfig,
46    attempt: usize,
47    deadline: Instant,
48}
49
50impl BackoffState {
51    pub fn new(config: BackoffConfig) -> Self {
52        let deadline = Instant::now() + config.total_timeout;
53        Self {
54            config,
55            attempt: 0,
56            deadline,
57        }
58    }
59
60    pub fn attempts(&self) -> usize {
61        self.attempt
62    }
63
64    pub fn has_time_remaining(&self) -> bool {
65        Instant::now() < self.deadline
66    }
67
68    pub fn can_retry(&self) -> bool {
69        self.attempt < self.config.max_attempts && self.has_time_remaining()
70    }
71
72    pub fn next_delay(&mut self) -> Duration {
73        if self.attempt == 0 {
74            self.attempt += 1;
75            return Duration::from_millis(0);
76        }
77
78        let exp = 2u64.pow((self.attempt - 1) as u32);
79        let base = self.config.initial_delay.mul_f64(exp as f64);
80        self.attempt += 1;
81
82        let capped = if base > self.config.max_delay {
83            self.config.max_delay
84        } else {
85            base
86        };
87
88        let jitter: f64 = rand::thread_rng().gen();
89        let jittered = capped.mul_f64(1.0 + jitter);
90        if jittered > self.config.max_delay {
91            self.config.max_delay
92        } else {
93            jittered
94        }
95    }
96}
97
98#[cfg(test)]
99mod tests {
100    use super::*;
101
102    #[test]
103    fn first_delay_is_zero() {
104        let mut backoff = BackoffState::new(BackoffConfig::standard_operation());
105        assert_eq!(backoff.next_delay(), Duration::from_millis(0));
106    }
107
108    #[test]
109    fn delays_increase_with_jitter() {
110        let mut backoff = BackoffState::new(BackoffConfig::standard_operation());
111        backoff.next_delay();
112        let d1 = backoff.next_delay();
113        backoff.next_delay();
114        let d2 = backoff.next_delay();
115        assert!(d2 >= d1);
116    }
117}
firebase_rs_sdk/storage/request/backoff.rs

firebase_rs_sdk/storage/request/
backoff.rs
