Add jitter to constant backoff

Cargo.toml

@@ -8,9 +8,9 @@ name = "backon"
 version = "0.4.0"
 
 [dependencies]
-futures = "0.3"
+fastrand = "1.9.0"
+futures-core = "0.3.26"
 pin-project = "1"
-rand = "0.8"
 tokio = { version = "1", features = ["time"] }
 
 [dev-dependencies]

src/constant.rs

@@ -35,13 +35,15 @@ use crate::backoff::BackoffBuilder;
 pub struct ConstantBuilder {
     delay: Duration,
     max_times: Option<usize>,
+    jitter: bool,
 }
 
 impl Default for ConstantBuilder {
     fn default() -> Self {
         Self {
             delay: Duration::from_secs(1),
             max_times: Some(3),
+            jitter: false,
         }
     }
 }
@@ -58,6 +60,12 @@ impl ConstantBuilder {
         self.max_times = Some(max_times);
         self
     }
+
+    /// Set jitter on
+    pub fn with_jitter(mut self) -> Self {
+        self.jitter = true;
+        self
+    }
 }
 
 impl BackoffBuilder for ConstantBuilder {
@@ -69,6 +77,7 @@ impl BackoffBuilder for ConstantBuilder {
             max_times: self.max_times,
 
             attempts: 0,
+            jitter: self.jitter,
         }
     }
 }
@@ -80,6 +89,7 @@ pub struct ConstantBackoff {
     max_times: Option<usize>,
 
     attempts: usize,
+    jitter: bool,
 }
 
 impl Default for ConstantBackoff {
@@ -88,6 +98,7 @@ impl Default for ConstantBackoff {
             delay: Duration::from_secs(1),
             max_times: Some(3),
             attempts: 0,
+            jitter: false,
         }
     }
 }
@@ -96,14 +107,18 @@ impl Iterator for ConstantBackoff {
     type Item = Duration;
 
     fn next(&mut self) -> Option<Self::Item> {
+        let delay = || match self.jitter {
+            true => self.delay + self.delay.mul_f32(fastrand::f32()),
+            false => self.delay,
+        };
         match self.max_times {
-            None => Some(self.delay),
+            None => Some(delay()),
             Some(max_times) => {
                 if self.attempts >= max_times {
                     None
                 } else {
                     self.attempts += 1;
-                    Some(self.delay)
+                    Some(delay())
                 }
             }
         }
@@ -146,4 +161,13 @@ mod tests {
         assert_eq!(Some(Duration::from_secs(1)), exp.next());
         assert_eq!(None, exp.next());
     }
+
+    #[test]
+    fn test_constant_with_jitter() {
+        let mut it = ConstantBuilder::default().with_jitter().build();
+
+        let dur = it.next().unwrap();
+        fastrand::seed(7);
+        assert!(dur > Duration::from_secs(1));
+    }
 }

src/exponential.rs

@@ -1,7 +1,5 @@
 use std::time::Duration;
 
-use rand::Rng;
-
 use crate::backoff::BackoffBuilder;
 
 /// ExponentialBuilder is used to build a [`ExponentialBackoff`]
@@ -149,9 +147,7 @@ impl Iterator for ExponentialBackoff {
 
                 // If jitter is enabled, add random jitter based on min delay.
                 if self.jitter {
-                    cur += self
-                        .min_delay
-                        .mul_f32(rand::thread_rng().gen_range(0.0..1.0));
+                    cur += self.min_delay.mul_f32(fastrand::f32());
                 }
 
                 Some(cur)
@@ -167,9 +163,7 @@ impl Iterator for ExponentialBackoff {
 
                 // If jitter is enabled, add random jitter based on min delay.
                 if self.jitter {
-                    cur += self
-                        .min_delay
-                        .mul_f32(rand::thread_rng().gen_range(0.0..1.0));
+                    cur += self.min_delay.mul_f32(fastrand::f32());
                 }
 
                 Some(cur)

src/retry.rs

@@ -4,7 +4,7 @@ use std::task::Context;
 use std::task::Poll;
 use std::time::Duration;
 
-use futures::ready;
+use futures_core::ready;
 use pin_project::pin_project;
 
 use crate::backoff::BackoffBuilder;