Attribute Macro retry_if::retry

#[retry]

Decorate a function with a given retry configuration.

Takes two arguments

• ExponentialBackoffConfig: type defined in parent crate that configures how to back off
• retry-if: a predicate that takes the same type as the output of the decorated function

Example: Retrying a Result-producing Function on Err(…)

The below example sets up a basic retry configuration that will retry up to five times, waiting at first 1 second, then 2 seconds, 4 seconds, etc.

There is no configured maximum time to retry across all attempts (t_wait_max), nor is there any maximum waiting time on each backoff (backoff_max).

const BACKOFF_CONFIG: ExponentialBackoffConfig = ExponentialBackoffConfig {
    max_retries: 5,
    t_wait: Duration::from_secs(1),
    backoff: 2.0,
    t_wait_max: None,
    backoff_max: None,
};

// this takes an address of the same type as the output of the decorated function
//  it returns a boolean specifying if the function should be retried based on the result
fn retry_if(result: &Result<i64, TryFromIntError>) -> bool {
    result.is_err()
}

#[retry(BACKOFF_CONFIG, retry_if)]
async fn fallible_call() -> Result<i64, TryFromIntError> {
    // this will always produce a TryFromIntError, triggering a retry
    i64::try_from(i128::MAX)
}