msy 0.4.2

Modern musl rsync alternative - Fast, parallel file synchronization
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
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
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302

use crate::error::SyncError;
use std::future::Future;
use std::time::Duration;

/// Configuration for retry logic with exponential backoff
#[derive(Debug, Clone)]
pub struct RetryConfig {
    /// Maximum number of retry attempts
    pub max_attempts: u32,
    /// Initial delay before first retry
    pub initial_delay: Duration,
    /// Maximum delay between retries
    pub max_delay: Duration,
    /// Backoff multiplier for exponential growth
    pub backoff_multiplier: f64,
}

impl Default for RetryConfig {
    fn default() -> Self {
        Self {
            max_attempts: 3,
            initial_delay: Duration::from_secs(1),
            max_delay: Duration::from_secs(30),
            backoff_multiplier: 2.0,
        }
    }
}

impl RetryConfig {
    /// Create a new RetryConfig with custom settings
    pub fn new(max_attempts: u32, initial_delay: Duration) -> Self {
        Self {
            max_attempts,
            initial_delay,
            ..Default::default()
        }
    }

    /// Set the maximum delay between retries
    #[allow(dead_code)] // Configuration builder - may be used for custom retry strategies
    pub fn with_max_delay(mut self, max_delay: Duration) -> Self {
        self.max_delay = max_delay;
        self
    }

    /// Set the backoff multiplier
    #[allow(dead_code)] // Configuration builder - may be used for custom retry strategies
    pub fn with_backoff_multiplier(mut self, multiplier: f64) -> Self {
        self.backoff_multiplier = multiplier;
        self
    }

    /// Calculate delay for a given attempt number (0-indexed)
    fn calculate_delay(&self, attempt: u32) -> Duration {
        let delay_secs =
            self.initial_delay.as_secs_f64() * self.backoff_multiplier.powi(attempt as i32);
        let delay = Duration::from_secs_f64(delay_secs);
        std::cmp::min(delay, self.max_delay)
    }
}

/// Retry an async operation with exponential backoff
///
/// This function will retry the operation up to `config.max_attempts` times
/// if it fails with a retryable error. The delay between retries increases
/// exponentially according to the backoff configuration.
///
/// # Example
///
/// ```ignore
/// let config = RetryConfig::default();
/// let result = retry_with_backoff(&config, || async {
///     // Your async operation here
///     Ok(())
/// }).await?;
/// ```
pub async fn retry_with_backoff<F, Fut, T>(
    config: &RetryConfig,
    mut operation: F,
) -> Result<T, SyncError>
where
    F: FnMut() -> Fut,
    Fut: Future<Output = Result<T, SyncError>>,
{
    let mut attempt = 0;

    loop {
        match operation().await {
            Ok(result) => return Ok(result),
            Err(e) if attempt >= config.max_attempts => {
                return Err(e);
            }
            Err(e) if e.is_retryable() => {
                let delay = config.calculate_delay(attempt);

                eprintln!(
                    "Attempt {}/{} failed: {}. Retrying in {:?}...",
                    attempt + 1,
                    config.max_attempts,
                    e,
                    delay
                );

                tokio::time::sleep(delay).await;
                attempt += 1;
            }
            Err(e) => {
                // Non-retryable error, fail immediately
                return Err(e);
            }
        }
    }
}

/// Convenience wrapper for retrying with default config
#[allow(dead_code)] // Helper function - may be used for simple retry scenarios
pub async fn retry_default<F, Fut, T>(operation: F) -> Result<T, SyncError>
where
    F: FnMut() -> Fut,
    Fut: Future<Output = Result<T, SyncError>>,
{
    retry_with_backoff(&RetryConfig::default(), operation).await
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::sync::atomic::{AtomicU32, Ordering};
    use std::sync::Arc;

    #[test]
    fn test_retry_config_default() {
        let config = RetryConfig::default();
        assert_eq!(config.max_attempts, 3);
        assert_eq!(config.initial_delay, Duration::from_secs(1));
        assert_eq!(config.max_delay, Duration::from_secs(30));
        assert_eq!(config.backoff_multiplier, 2.0);
    }

    #[test]
    fn test_retry_config_custom() {
        let config = RetryConfig::new(5, Duration::from_millis(500))
            .with_max_delay(Duration::from_secs(60))
            .with_backoff_multiplier(3.0);

        assert_eq!(config.max_attempts, 5);
        assert_eq!(config.initial_delay, Duration::from_millis(500));
        assert_eq!(config.max_delay, Duration::from_secs(60));
        assert_eq!(config.backoff_multiplier, 3.0);
    }

    #[test]
    fn test_calculate_delay_exponential() {
        let config = RetryConfig::default();

        // First retry: 1s * 2^0 = 1s
        assert_eq!(config.calculate_delay(0), Duration::from_secs(1));

        // Second retry: 1s * 2^1 = 2s
        assert_eq!(config.calculate_delay(1), Duration::from_secs(2));

        // Third retry: 1s * 2^2 = 4s
        assert_eq!(config.calculate_delay(2), Duration::from_secs(4));

        // Fourth retry: 1s * 2^3 = 8s
        assert_eq!(config.calculate_delay(3), Duration::from_secs(8));
    }

    #[test]
    fn test_calculate_delay_capped_at_max() {
        let config = RetryConfig {
            initial_delay: Duration::from_secs(10),
            max_delay: Duration::from_secs(15),
            backoff_multiplier: 2.0,
            max_attempts: 5,
        };

        // First retry: 10s * 2^0 = 10s (under max)
        assert_eq!(config.calculate_delay(0), Duration::from_secs(10));

        // Second retry: 10s * 2^1 = 20s, capped at 15s
        assert_eq!(config.calculate_delay(1), Duration::from_secs(15));

        // Third retry: 10s * 2^2 = 40s, capped at 15s
        assert_eq!(config.calculate_delay(2), Duration::from_secs(15));
    }

    #[tokio::test]
    async fn test_retry_success_first_attempt() {
        let counter = Arc::new(AtomicU32::new(0));
        let counter_clone = counter.clone();

        let config = RetryConfig::default();
        let result = retry_with_backoff(&config, || {
            let c = counter_clone.clone();
            async move {
                c.fetch_add(1, Ordering::SeqCst);
                Ok::<_, SyncError>(42)
            }
        })
        .await;

        assert_eq!(result.unwrap(), 42);
        assert_eq!(counter.load(Ordering::SeqCst), 1);
    }

    #[tokio::test]
    async fn test_retry_success_after_retries() {
        let counter = Arc::new(AtomicU32::new(0));
        let counter_clone = counter.clone();

        let config = RetryConfig::new(3, Duration::from_millis(10));
        let result = retry_with_backoff(&config, || {
            let c = counter_clone.clone();
            async move {
                let count = c.fetch_add(1, Ordering::SeqCst);
                if count < 2 {
                    // Fail first 2 attempts with retryable error
                    Err(SyncError::NetworkTimeout {
                        duration: Duration::from_secs(1),
                    })
                } else {
                    Ok(42)
                }
            }
        })
        .await;

        assert_eq!(result.unwrap(), 42);
        assert_eq!(counter.load(Ordering::SeqCst), 3); // 2 failures + 1 success
    }

    #[tokio::test]
    async fn test_retry_exhausted() {
        let counter = Arc::new(AtomicU32::new(0));
        let counter_clone = counter.clone();

        let config = RetryConfig::new(2, Duration::from_millis(10));
        let result = retry_with_backoff(&config, || {
            let c = counter_clone.clone();
            async move {
                c.fetch_add(1, Ordering::SeqCst);
                Err::<i32, _>(SyncError::NetworkTimeout {
                    duration: Duration::from_secs(1),
                })
            }
        })
        .await;

        assert!(result.is_err());
        assert!(matches!(
            result.unwrap_err(),
            SyncError::NetworkTimeout { .. }
        ));
        // Initial attempt + 2 retries = 3 total
        assert_eq!(counter.load(Ordering::SeqCst), 3);
    }

    #[tokio::test]
    async fn test_retry_non_retryable_error() {
        let counter = Arc::new(AtomicU32::new(0));
        let counter_clone = counter.clone();

        let config = RetryConfig::default();
        let result = retry_with_backoff(&config, || {
            let c = counter_clone.clone();
            async move {
                c.fetch_add(1, Ordering::SeqCst);
                Err::<i32, _>(SyncError::NetworkFatal {
                    message: "Fatal error".to_string(),
                })
            }
        })
        .await;

        assert!(result.is_err());
        assert!(matches!(
            result.unwrap_err(),
            SyncError::NetworkFatal { .. }
        ));
        // Should fail immediately without retries
        assert_eq!(counter.load(Ordering::SeqCst), 1);
    }

    #[tokio::test]
    async fn test_retry_default_wrapper() {
        let counter = Arc::new(AtomicU32::new(0));
        let counter_clone = counter.clone();

        let result = retry_default(|| {
            let c = counter_clone.clone();
            async move {
                c.fetch_add(1, Ordering::SeqCst);
                Ok::<_, SyncError>(100)
            }
        })
        .await;

        assert_eq!(result.unwrap(), 100);
        assert_eq!(counter.load(Ordering::SeqCst), 1);
    }
}