Apply suggestions from code review #1002

Co-authored-by: Waffle Maybe <waffle.lapkin@gmail.com>

CHANGELOG.md

@@ -51,7 +51,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Greatly improved the speed of graceful shutdown (`^C`) ([PR 938](https://github.com/teloxide/teloxide/pull/938))
 - Fix typos in docstrings ([PR 953](https://github.com/teloxide/teloxide/pull/953))
 - Use `Seconds` instead of `String` in `InlineQueryResultAudio` for `audio_duration` ([PR 994](https://github.com/teloxide/teloxide/pull/994))
-- Issue [#780](https://github.com/teloxide/teloxide/issues/780) ([PR 1002](https://github.com/teloxide/teloxide/pull/1002))
+- High CPU usage on network errors ([PR 1002](https://github.com/teloxide/teloxide/pull/1002), [Issue 780](https://github.com/teloxide/teloxide/issues/780))
 
 ### Changed
 

crates/teloxide/src/backoff_strategy.rs

@@ -1,10 +1,10 @@
 use std::time::Duration;
 
-pub type BackoffStrategy = Box<dyn Fn(u32) -> Duration + Send>;
+pub type BackoffStrategy = Box<dyn Send + Fn(u32) -> Duration>;
 
 /// Calculates the backoff time in seconds for exponential strategy with base 2
 ///
 /// More at: <https://en.wikipedia.org/wiki/Exponential_backoff#Exponential_backoff_algorithm>
 pub fn exponential_backoff_strategy(error_count: u32) -> Duration {
-    Duration::from_secs(2_u64.pow(error_count))
+    Duration::from_secs((1_u64 << error_count).min(30 * 60))
 }

crates/teloxide/src/update_listeners/polling.rs

@@ -88,9 +88,9 @@ where
     }
 
     /// The backoff strategy that will be used for delay calculation between
-    /// reconnections
+    /// reconnections caused by network errors.
     ///
-    /// By default, the [`exponential_backoff_strategy`] is used
+    /// By default, the [`exponential_backoff_strategy`] is used.
     pub fn backoff_strategy(self, backoff_strategy: BackoffStrategy) -> Self {
         Self { backoff_strategy, ..self }
     }
@@ -462,7 +462,7 @@ impl<B: Requester> Stream for PollingStream<'_, B> {
             }
         }
         // Poll eepy future until completion, needed for backoff strategy
-        if let Some(eepy) = this.eepy.as_mut().as_pin_mut() {
+        else if let Some(eepy) = this.eepy.as_mut().as_pin_mut() {
             match eepy.poll(cx) {
                 Poll::Ready(_) => {
                     // As soon as delay is waited we increment the counter