Unverified Commit 0d80212a authored by Russell Cohen's avatar Russell Cohen Committed by GitHub
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Avoid overflow in exponential backoff computation (#3229) 

## Motivation and Context
aws-sdk-rust#960

## Description
Use checked_pow to avoid overflow in backoff computation

## Testing
- unit test

## Checklist
<!--- If a checkbox below is not applicable, then please DELETE it
rather than leaving it unchecked -->
- [x] I have updated `CHANGELOG.next.toml` if I made changes to the
smithy-rs codegen or runtime crates
- [x] I have updated `CHANGELOG.next.toml` if I made changes to the AWS
SDK, generated SDK code, or SDK runtime crates

----

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parent e3a57c88

CHANGELOG.next.toml

+12 −0
Original line number Diff line number Diff line
@@ -54,3 +54,15 @@ message = "Make certain types for EMR Serverless optional. Previously, they defa 
references = ["smithy-rs#3217"]

meta = { "breaking" = true, "tada" = false, "bug" = true }

author = "milesziemer"



[[smithy-rs]]

message = "Prevent multiplication overflow in backoff computation"

references = ["smithy-rs#3229", "aws-sdk-rust#960"]

meta = { "breaking" = false, "tada" = false, "bug" = true, target = "client" }

author = "rcoh"



[[aws-sdk-rust]]

message = "Prevent multiplication overflow in backoff computation"

references = ["smithy-rs#3229", "aws-sdk-rust#960"]

meta = { "breaking" = false, "tada" = false, "bug" = true }

author = "rcoh"

rust-runtime/aws-smithy-runtime/src/client/retries/strategy/standard.rs

+13 −1
Original line number Diff line number Diff line
@@ -286,7 +286,10 @@ fn check_rate_limiter_for_delay( 
}



fn calculate_exponential_backoff(base: f64, initial_backoff: f64, retry_attempts: u32) -> f64 {

    base * initial_backoff * 2_u32.pow(retry_attempts) as f64

    2_u32

        .checked_pow(retry_attempts)

        .map(|backoff| (backoff as f64) * base * initial_backoff)

        .unwrap_or(f64::MAX)

}



fn get_seconds_since_unix_epoch(runtime_components: &RuntimeComponents) -> f64 {
@@ -793,4 +796,13 @@ mod tests { 
            assert_eq!(expected_backoff, actual_backoff);

        }

    }



    #[test]

    fn calculate_backoff_overflow() {

        // avoid overflow for a silly large amount of retry attempts

        assert_eq!(

            calculate_exponential_backoff(1_f64, 10_f64, 100000),

            f64::MAX

        );

    }

}