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
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190

use std::{
    marker::PhantomData,
    sync::{
        atomic::{AtomicU64, Ordering},
        Arc,
    },
    time::Duration,
};

use futures::{future::BoxFuture, FutureExt};
use humantime::format_duration;
use tower::retry::Policy;

const DEFAULT_MAX_SECS_TO_WAIT: u64 = 128;

/// Retry Policy.
#[derive(Debug)]
pub enum RetryPolicy<T, U, F = ()> {
    /// On.
    On {
        /// Error filter.
        f: F,
        /// Retry times.
        times: usize,
        /// Max secs to wait.
        max_secs: u64,
    },
    /// Never.
    Never(PhantomData<fn() -> (T, U)>),
}

impl<T, U, F: Clone> Clone for RetryPolicy<T, U, F> {
    fn clone(&self) -> Self {
        match self {
            Self::Never(_) => Self::Never(PhantomData),
            Self::On { f, times, max_secs } => Self::On {
                f: f.clone(),
                times: *times,
                max_secs: *max_secs,
            },
        }
    }
}

impl<T, U, F: Copy> Copy for RetryPolicy<T, U, F> {}

impl<T, U> Default for RetryPolicy<T, U, ()> {
    fn default() -> Self {
        Self::never()
    }
}

impl<T, U, F> RetryPolicy<T, U, F> {
    /// Never retry.
    pub fn never() -> Self {
        Self::Never(PhantomData)
    }

    /// Retry on.
    pub fn retry_on<E, F2>(self, f: F2) -> RetryPolicy<T, U, F2>
    where
        F2: Fn(&E) -> bool,
        F2: Send + 'static + Clone,
    {
        RetryPolicy::On {
            f,
            times: 0,
            max_secs: DEFAULT_MAX_SECS_TO_WAIT,
        }
    }

    /// Retry on with max wait secs.
    pub fn retry_on_with_max_wait_secs<E, F2>(self, f: F2, secs: u64) -> RetryPolicy<T, U, F2>
    where
        F2: Fn(&E) -> bool,
        F2: Send + 'static + Clone,
    {
        RetryPolicy::On {
            f,
            times: 0,
            max_secs: secs,
        }
    }
}

impl<T, U, E, F> Policy<T, U, E> for RetryPolicy<T, U, F>
where
    T: 'static + Clone,
    U: 'static,
    F: Fn(&E) -> bool,
    F: Send + 'static + Clone,
{
    type Future = BoxFuture<'static, Self>;

    fn retry(&self, _req: &T, result: Result<&U, &E>) -> Option<Self::Future> {
        match self {
            Self::On { f, times, max_secs } => match result {
                Ok(_) => None,
                Err(err) => {
                    if f(err) {
                        let times = *times;
                        let secs = (1 << times).min(*max_secs);
                        tracing::trace!("retry in {secs}s;");
                        let retry = Self::On {
                            f: f.clone(),
                            times: times + 1,
                            max_secs: *max_secs,
                        };
                        let fut = async move {
                            tokio::time::sleep(std::time::Duration::from_secs(secs)).await;
                            retry
                        }
                        .boxed();
                        Some(fut)
                    } else {
                        tracing::trace!("retry given up;");
                        None
                    }
                }
            },
            Self::Never(_) => None,
        }
    }

    fn clone_request(&self, req: &T) -> Option<T> {
        Some(req.clone())
    }
}

/// Always.
#[derive(Debug, Clone)]
pub struct Always {
    times: Arc<AtomicU64>,
    max_duration: Duration,
}

impl Default for Always {
    fn default() -> Self {
        Self {
            times: Arc::new(AtomicU64::new(0)),
            max_duration: Duration::from_secs(DEFAULT_MAX_SECS_TO_WAIT),
        }
    }
}

impl Always {
    /// Create a new always retry policy with max duration to wait.
    pub fn with_max_duration(dur: Duration) -> Self {
        Self {
            times: Arc::new(AtomicU64::new(0)),
            max_duration: dur,
        }
    }
}

impl<T, U, E> Policy<T, U, E> for Always
where
    T: Clone,
    E: std::fmt::Display,
{
    type Future = BoxFuture<'static, Self>;

    fn clone_request(&self, req: &T) -> Option<T> {
        Some(req.clone())
    }

    fn retry(&self, _req: &T, result: Result<&U, &E>) -> Option<Self::Future> {
        match result {
            Ok(_) => {
                self.times.store(0, Ordering::Release);
                None
            }
            Err(err) => {
                let times = self.times.fetch_add(1, Ordering::AcqRel);
                let max_duration = self.max_duration;
                let dur = Duration::from_secs(1 << times).min(max_duration);
                tracing::error!("request error: {err}, retry in {}", format_duration(dur));
                let shared = self.times.clone();
                let fut = async move {
                    tokio::time::sleep(dur).await;
                    Self {
                        times: shared,
                        max_duration,
                    }
                };
                Some(fut.boxed())
            }
        }
    }
}