apalis-core 1.0.0

Core for apalis: simple, extensible multithreaded background processing for Rust
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129

use std::{
    task::{Context, Poll},
    time::Duration,
};

use futures_timer::Delay;
use futures_util::FutureExt;
use rand::RngExt;

use crate::backend::ext::poll_strategy::{PollSnapshot, PollStrategy};

/// A polling strategy that applies exponential backoff to an inner interval strategy
#[derive(Debug)]
pub struct BackoffStrategy {
    default_delay: Duration,
    current_delay: Duration,
    backoff_config: BackoffConfig,
    delay: Option<Delay>,
}

impl Clone for BackoffStrategy {
    fn clone(&self) -> Self {
        Self {
            default_delay: self.default_delay,
            current_delay: self.current_delay,
            backoff_config: self.backoff_config.clone(),
            delay: None,
        }
    }
}

impl BackoffStrategy {
    /// Create a new BackoffStrategy with the given BackoffConfig
    #[must_use]
    pub fn new(default_delay: Duration, config: BackoffConfig) -> Self {
        Self {
            default_delay,
            current_delay: default_delay,
            backoff_config: config,
            delay: None,
        }
    }
}

impl PollStrategy for BackoffStrategy {
    fn poll_drive(&mut self, cx: &mut Context<'_>, _: &PollSnapshot) -> Poll<Option<()>> {
        let delay = self
            .delay
            .get_or_insert_with(|| Delay::new(self.current_delay));
        match delay.poll_unpin(cx) {
            Poll::Pending => Poll::Pending,
            Poll::Ready(_) => {
                self.delay = None;
                Poll::Ready(Some(()))
            }
        }
    }

    fn on_poll(&mut self, ctx: &PollSnapshot) {
        self.current_delay = if ctx.is_idle() {
            self.backoff_config
                .next_delay(self.default_delay, self.current_delay, true)
        } else {
            self.default_delay
        };
    }
}

/// Backoff configuration for strategies
#[derive(Debug, Clone)]
pub struct BackoffConfig {
    max_delay: Duration,
    multiplier: f64,
    jitter_factor: f64, // 0.0 to 1.0
}

impl Default for BackoffConfig {
    fn default() -> Self {
        Self {
            max_delay: Duration::from_secs(60),
            multiplier: 2.0,
            jitter_factor: 0.1,
        }
    }
}

impl BackoffConfig {
    /// Create a new BackoffConfig with the specified maximum delay
    #[must_use]
    pub fn new(max: Duration) -> Self {
        Self {
            max_delay: max,
            ..Default::default()
        }
    }

    /// Set the multiplier for exponential backoff
    #[must_use]
    pub fn with_multiplier(mut self, multiplier: f64) -> Self {
        self.multiplier = multiplier;
        self
    }

    /// Set the jitter factor (0.0 to 1.0) for randomizing delays
    #[must_use]
    pub fn with_jitter(mut self, jitter_factor: f64) -> Self {
        self.jitter_factor = jitter_factor.clamp(0.0, 1.0);
        self
    }

    /// Calculate the next delay with backoff and jitter
    fn next_delay(&self, default_delay: Duration, current_delay: Duration, idle: bool) -> Duration {
        let base_delay = if idle {
            let next = Duration::from_secs_f64(current_delay.as_secs_f64() * self.multiplier);
            next.min(self.max_delay)
        } else {
            default_delay
        };

        if self.jitter_factor > 0.0 {
            let jitter_range = base_delay.as_secs_f64() * self.jitter_factor;
            let jitter = rand::rng().random_range(-jitter_range..=jitter_range);
            let jittered = base_delay.as_secs_f64() + jitter;
            Duration::from_secs_f64(jittered.max(0.0))
        } else {
            base_delay
        }
    }
}