Adaptive backoff provides a mechanism to intelligently back off use of rate limited or failure operations through sources simples structs, Backoffs. Backoffs take input on success and failure, then return a duration to wait.

For an adaptive backoff, as the failure and success calls increase the returned duration eventually converges on a value to avoid rate limiting of requests.

Include within your Cargo.toml:

adaptive_backoff = "0.2"

And follow an example below:

Below is an example of an adapative ExponentialBackoff which works from a queue and converges on a minimal delay duration between calls. It grows by a factor of 2.0 to a maximum of 300 seconds.

use std::time::Duration;
use adaptive_backoff::prelude::*;

let mut backoff = ExponentialBackoffBuilder::default()
    .factor(2.0)
    .max(Duration::from_secs(300))
    .adaptive()
    .build()
    .unwrap();

while let Some(item) = queue.pop() {
    loop {
        match worker_iter(&conn, &item).await {
            Ok(_) => {
                delay_for(backoff.success()).await;
                break;
            }
            Err(_) => delay_for(backoff.fail()).await,
        }
    }
}

If adaptive is omitted from the example above, a simple backoff is returned. Its API lacks success() and fail(), instead it can only return increasing delays with wait() until reset() is called to return it.

use std::time::Duration;
use adaptive_backoff::prelude::*;

let mut backoff = ExponentialBackoffBuilder::default()
    .factor(2.0)
    .max(Duration::from_secs(30))
    .build()
    .unwrap();

while let Some(item) = queue.pop() {
    loop {
        match worker_iter(&conn, &item).await {
            Ok(_) => {
                delay_for(backoff.wait()).await;
                break;
            }
            Err(_) => delay_for(backoff.wait()).await,
        }
    }

    backoff.reset();
}

There are tests for backoff implementations which contain example use of the external API with expected output. See both the simple exponential example and the adaptive exponential backoff example.