Struct RetryFuture

pub struct RetryFuture<MakeFutureT, FutureT, BackoffT, OnRetryT> { /* private fields */ }

A retryable future.

Can be created by calling retry_fn.

Implementations

impl<MakeFutureT, FutureT, BackoffT, T, E, OnRetryT> RetryFuture<MakeFutureT, FutureT, BackoffT, OnRetryT>

where MakeFutureT: FnMut() -> FutureT, FutureT: Future<Output = Result<T, E>>,

pub fn max_delay(self, delay: Duration) -> Self

Set the max duration to sleep between each attempt.

pub fn no_backoff( self, ) -> RetryFuture<MakeFutureT, FutureT, NoBackoff, OnRetryT>

Remove the backoff strategy.

This will make the future be retried immediately without any delay in between attempts.

pub fn exponential_backoff( self, initial_delay: Duration, ) -> RetryFuture<MakeFutureT, FutureT, ExponentialBackoff, OnRetryT>

Use exponential backoff for retrying the future.

The first delay will be initial_delay and afterwards the delay will double every time.

pub fn fixed_backoff( self, delay: Duration, ) -> RetryFuture<MakeFutureT, FutureT, FixedBackoff, OnRetryT>

Use a fixed backoff for retrying the future.

The delay between attempts will always be delay.

pub fn linear_backoff( self, delay: Duration, ) -> RetryFuture<MakeFutureT, FutureT, LinearBackoff, OnRetryT>

Use a linear backoff for retrying the future.

The delay will be delay * attempt so it’ll scale linear with the attempt.

pub fn custom_backoff<B>( self, backoff_strategy: B, ) -> RetryFuture<MakeFutureT, FutureT, B, OnRetryT>

where for<'a> B: BackoffStrategy<'a, E>,

Use a custom backoff specified by some function.

use std::time::Duration;

tryhard::retry_fn(|| read_file("Cargo.toml"))
    .retries(10)
    .custom_backoff(|attempt, _error: &std::io::Error| {
        if attempt < 5 {
            Duration::from_millis(100)
        } else {
            Duration::from_millis(500)
        }
    })
    .await?;

You can also stop retrying early:

use std::time::Duration;
use tryhard::RetryPolicy;

tryhard::retry_fn(|| read_file("Cargo.toml"))
    .retries(10)
    .custom_backoff(|attempt, error: &std::io::Error| {
        if error.to_string().contains("foobar") {
            // returning this will cancel the loop and
            // return the most recent error
            RetryPolicy::Break
        } else {
            RetryPolicy::Delay(Duration::from_millis(50))
        }
    })
    .await?;

pub fn on_retry<F, OnRetryFut>( self, f: F, ) -> RetryFuture<MakeFutureT, FutureT, BackoffT, F>

where F: Fn(u32, Option<Duration>, &E) -> OnRetryFut,

Some async computation that will be spawned before each retry.

This can for example be used for telemtry such as logging or other kinds of tracking.

The future returned will be given to tokio::spawn so wont impact the actual retrying.

Example

For example to print and gather all the errors you can do:

use std::sync::Arc;
use tokio::sync::Mutex;

let all_errors = Arc::new(Mutex::new(Vec::new()));

tryhard::retry_fn(|| async {
    // just some dummy computation that always fails
    Err::<(), _>("fail")
})
    .retries(10)
    .on_retry(|_attempt, _next_delay, error: &&'static str| {
        // the future must be `'static` so it cannot contain references
        let all_errors = Arc::clone(&all_errors);
        let error = error.clone();
        async move {
            eprintln!("Something failed: {}", error);
            all_errors.lock().await.push(error);
        }
    })
    .await
    .unwrap_err();

assert_eq!(all_errors.lock().await.len(), 10);

Trait Implementations

impl<F, Fut, B, T, E, OnRetryT> Future for RetryFuture<F, Fut, B, OnRetryT>

where F: FnMut() -> Fut, Fut: Future<Output = Result<T, E>>, for<'a> B: BackoffStrategy<'a, E>, for<'a> <B as BackoffStrategy<'a, E>>::Output: Into<RetryPolicy>, OnRetryT: OnRetry<E>,

type Output = Result<T, E>

The type of value produced on completion.

fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output>

Attempts to resolve the future to a final value, registering the current task for wakeup if the value is not yet available.

impl<'__pin, MakeFutureT, FutureT, BackoffT, OnRetryT> Unpin for RetryFuture<MakeFutureT, FutureT, BackoffT, OnRetryT>

where PinnedFieldsOf<__Origin<'__pin, MakeFutureT, FutureT, BackoffT, OnRetryT>>: Unpin,