Struct retry_if::ExponentialBackoffConfig

source ·

pub struct ExponentialBackoffConfig {
    pub max_retries: i32,
    pub t_wait: Duration,
    pub backoff: f64,
    pub t_wait_max: Option<Duration>,
    pub backoff_max: Option<Duration>,
}

Expand description

Configuration for an exponential backoff, allowing control over the entire strategy.

This will retry a failing operation up to max_tries, waiting for a duration of t_wait on the first failure and t_wait * backoff**attempt for all remaining attempts. The maximum single wait can be capped by backoff_max, and the total waiting time before failing can be set with t_wait_max.

The behavior of t_wait_max is such that the function guarantees it will not begin sleeping if sleeping would cause the function to exceed a total execution time of t_wait_max. It is however possible for the execution to exceed t_wait_max if the decorated code (e.g. calling an API) causes it to exceed this time.

§Example: Classic Exponential Backoff

This backoff configuration will retry up to 5 times, waiting 1 second at first, then 2 seconds, 4 seconds, etc.


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

§Example: Constant Linear Retries

This configuration will retry up to five times, with no exponential behavior, since the backoff exponent is 1.0. It will wait 1 second for all retry attempts.


const BACKOFF_CONFIG: ExponentialBackoffConfig = ExponentialBackoffConfig {
    max_retries: 5,
    t_wait: Duration::from_secs(1),
    backoff: 1.0,
    t_wait_max: None,
    backoff_max: None,
};

§Example: Backoff With a Maximum Wait Time

This backoff configuration will retry up to 25 times, doubling the wait with each retry.

Setting t_wait_max to 10 minutes means that regardless of the number of retries or backoff exponent, it will return in 10 minutes or less.


const BACKOFF_CONFIG: ExponentialBackoffConfig = ExponentialBackoffConfig {
    max_retries: 25,
    t_wait: Duration::from_secs(1),
    backoff: 2.0,
    t_wait_max: Some(Duration::from_secs(600)),
    backoff_max: None,
};

§Example: Limited Backoff

This backoff configuration will retry up to 15 times, waiting 1 second at first, then 2 seconds, 4 seconds, etc.

Setting backoff_max to 30 seconds ensures it will exponentially back off until reaching a 30s wait time, then will continue to retry every 30s until it succeeds, exhausts retries, or hits t_wait_max (not configured in this case).


const BACKOFF_CONFIG: ExponentialBackoffConfig = ExponentialBackoffConfig {
    max_retries: 15,
    t_wait: Duration::from_secs(1),
    backoff: 2.0,
    t_wait_max: None,
    backoff_max: Some(Duration::from_secs(30)),
};