150 lines
3.9 KiB
Rust
150 lines
3.9 KiB
Rust
use std::time::Duration;
|
|
use rand::Rng;
|
|
use tracing::{info, warn};
|
|
|
|
/// Reconnection strategy with exponential backoff and jitter.
|
|
pub struct ReconnectStrategy {
|
|
/// Base delay (default: 1 second).
|
|
pub base_delay: Duration,
|
|
/// Maximum delay cap (default: 30 seconds).
|
|
pub max_delay: Duration,
|
|
/// Maximum number of attempts before giving up (0 = infinite).
|
|
pub max_attempts: u32,
|
|
/// Current attempt counter.
|
|
attempts: u32,
|
|
}
|
|
|
|
impl Default for ReconnectStrategy {
|
|
fn default() -> Self {
|
|
Self {
|
|
base_delay: Duration::from_secs(1),
|
|
max_delay: Duration::from_secs(30),
|
|
max_attempts: 0,
|
|
attempts: 0,
|
|
}
|
|
}
|
|
}
|
|
|
|
impl ReconnectStrategy {
|
|
pub fn new(base_delay: Duration, max_delay: Duration, max_attempts: u32) -> Self {
|
|
Self {
|
|
base_delay,
|
|
max_delay,
|
|
max_attempts,
|
|
attempts: 0,
|
|
}
|
|
}
|
|
|
|
/// Get the next backoff delay, or None if max attempts exceeded.
|
|
pub fn next_delay(&mut self) -> Option<Duration> {
|
|
if self.max_attempts > 0 && self.attempts >= self.max_attempts {
|
|
warn!("Max reconnection attempts ({}) exceeded", self.max_attempts);
|
|
return None;
|
|
}
|
|
|
|
let base_ms = self.base_delay.as_millis() as u64;
|
|
let exp_ms = base_ms.saturating_mul(1u64 << self.attempts.min(20));
|
|
let max_ms = self.max_delay.as_millis() as u64;
|
|
let capped_ms = exp_ms.min(max_ms);
|
|
|
|
// Add jitter: ±25%
|
|
let jitter_range = capped_ms / 4;
|
|
let jitter = if jitter_range > 0 {
|
|
rand::thread_rng().gen_range(0..jitter_range * 2) as i64 - jitter_range as i64
|
|
} else {
|
|
0
|
|
};
|
|
let final_ms = (capped_ms as i64 + jitter).max(0) as u64;
|
|
|
|
self.attempts += 1;
|
|
let delay = Duration::from_millis(final_ms);
|
|
info!(
|
|
"Reconnect attempt {} in {:?}",
|
|
self.attempts, delay
|
|
);
|
|
Some(delay)
|
|
}
|
|
|
|
/// Reset the attempt counter (on successful connection).
|
|
pub fn reset(&mut self) {
|
|
self.attempts = 0;
|
|
}
|
|
|
|
/// Current attempt number.
|
|
pub fn attempts(&self) -> u32 {
|
|
self.attempts
|
|
}
|
|
}
|
|
|
|
/// Session resume token — opaque blob the client sends to resume a session.
|
|
#[derive(Debug, Clone)]
|
|
pub struct SessionToken {
|
|
pub token: Vec<u8>,
|
|
}
|
|
|
|
impl SessionToken {
|
|
/// Generate a random session token.
|
|
pub fn generate() -> Self {
|
|
let mut token = vec![0u8; 32];
|
|
rand::thread_rng().fill(&mut token[..]);
|
|
Self { token }
|
|
}
|
|
|
|
pub fn from_bytes(data: Vec<u8>) -> Self {
|
|
Self { token: data }
|
|
}
|
|
|
|
pub fn as_bytes(&self) -> &[u8] {
|
|
&self.token
|
|
}
|
|
}
|
|
|
|
#[cfg(test)]
|
|
mod tests {
|
|
use super::*;
|
|
|
|
#[test]
|
|
fn exponential_backoff() {
|
|
let mut strategy = ReconnectStrategy::new(
|
|
Duration::from_millis(100),
|
|
Duration::from_secs(5),
|
|
5,
|
|
);
|
|
|
|
// Should get 5 delays
|
|
for i in 0..5 {
|
|
let delay = strategy.next_delay();
|
|
assert!(delay.is_some(), "attempt {} should succeed", i);
|
|
}
|
|
|
|
// 6th should fail
|
|
assert!(strategy.next_delay().is_none());
|
|
}
|
|
|
|
#[test]
|
|
fn reset_restores_attempts() {
|
|
let mut strategy = ReconnectStrategy::new(
|
|
Duration::from_millis(100),
|
|
Duration::from_secs(5),
|
|
2,
|
|
);
|
|
|
|
strategy.next_delay();
|
|
strategy.next_delay();
|
|
assert!(strategy.next_delay().is_none());
|
|
|
|
strategy.reset();
|
|
assert_eq!(strategy.attempts(), 0);
|
|
assert!(strategy.next_delay().is_some());
|
|
}
|
|
|
|
#[test]
|
|
fn session_token_generation() {
|
|
let token = SessionToken::generate();
|
|
assert_eq!(token.as_bytes().len(), 32);
|
|
|
|
let token2 = SessionToken::generate();
|
|
assert_ne!(token.as_bytes(), token2.as_bytes()); // extremely unlikely to be equal
|
|
}
|
|
}
|