futures-retry-policies

A crate to help retry futures.

use futures_retry_policies::{retry, RetryPolicy};
use std::{ops::ControlFlow, time::Duration};

// 1. Create your retry policy

/// Retries a request n times
pub struct Retries(usize);

// 2. Define how your policy behaves

impl RetryPolicy<Result<(), &'static str>> for Retries {
    fn should_retry(&mut self, result: Result<(), &'static str>) -> ControlFlow<Result<(), &'static str>, Duration> {
        if self.0 > 0 && result.is_err() {
            self.0 -= 1;
            // continue to retry on error
            ControlFlow::Continue(Duration::from_millis(100))
        } else {
            // We've got a success, or we've exhausted our retries, so break
            ControlFlow::Break(result)
        }
    }
}

/// Makes a request, like a HTTP request or gRPC request which you want to retry
async fn make_request() -> Result<(), &'static str>  {
    // make a request
    # static COUNT: std::sync::atomic::AtomicUsize = std::sync::atomic::AtomicUsize::new(0);
    # if COUNT.fetch_add(1, std::sync::atomic::Ordering::SeqCst) < 2 { Err("fail") } else { Ok(()) }
}

#[tokio::main]
async fn main() -> Result<(), &'static str> {
    // 3. Await the retry with your policy, a sleep function, and your async function.
    retry(Retries(3), tokio::time::sleep, make_request).await
}

Tracing

Add the tracing feature and you can use the Traced RetryPolicy to automatically log your retries

Tokio

Add the tokio feature and you can use the convenience tokio retry methods to skip specifying [tokio::time::sleep].

You can also use the [tokio::RetryFutureExt] trait to support calling retry directly on async functions.

#[tokio::main]
async fn main() -> Result<(), &'static str> {
    make_request.retry(Retries(3)).await
}

retry-policies

This crate has first class support for the retry-policies crate

use futures_retry_policies::{retry, retry_policies::{ShouldRetry, RetryPolicies}};
use retry_policies::policies::ExponentialBackoff;

enum Error { Retry, DoNotRetry }
impl ShouldRetry for Error {
    fn should_retry(&self, _: u32) -> bool { matches!(self, Error::Retry) }
}
async fn make_request() -> Result<(), Error>  {
    // make a request
    # static COUNT: std::sync::atomic::AtomicUsize = std::sync::atomic::AtomicUsize::new(0);
    # if COUNT.fetch_add(1, std::sync::atomic::Ordering::SeqCst) < 2 { Err(Error::Retry) } else { Ok(()) }
}

#[tokio::main]
async fn main() -> Result<(), Error> {
    let backoff = ExponentialBackoff::builder().build_with_max_retries(3);
    let policy = RetryPolicies::new(backoff);
    retry(policy, tokio::time::sleep, make_request).await
}