try-again

Retry synchronous or asynchronous operations until they no longer can or need to be retried.

Provides fn retry for retrying synchronous operations.

Provides async fn retry_async for retrying asynchronous operations.

Supports closures and function pointers.

The retried operation may return any type that implements NeedsRetry. This trait is already implemented for Result, Option and ExitStatus, allowing you to retry common fallible outcomes.

Synchronous example

use assertr::prelude::*;
use try_again::{delay, retry, IntoStdDuration};

async fn do_smth() {
    fn fallible_operation() -> Result<(), ()> {
        Ok(())
    }

    let final_outcome = retry(fallible_operation)
        .delayed_by(delay::Fixed::of(125.millis()).take(5));

    assert_that(final_outcome).is_ok();
}

Asynchronous example

use assertr::prelude::*;
use try_again::{delay, retry_async, IntoStdDuration};

async fn do_smth() {
    async fn fallible_operation() -> Result<(), ()> {
        Ok(())
    }

    let final_outcome = retry_async(fallible_operation)
        .delayed_by(delay::ExponentialBackoff::of_initial_delay(125.millis()).capped_at(2.secs()).take(10))
        .await;

    assert_that(final_outcome).is_ok();
}

Details

Delay strategies

delayed_by accepts a delay strategy. The delay module provides the following implementations

• None: No delay is applied.
• Fixed: A static delay.
• ExponentialBackoff: An exponentially increasing delay

All work with std::time::Duration, re-exposed as StdDuration. The IntoStdDuration can be used for a fluent syntax when defining durations, like in

use try_again::{delay, IntoStdDuration};

delay::Fixed::of(250.millis())

Delay executors

The standard retry and retry_async functions have the following default behavior:

• retry puts the current thread to sleep between retries (through the provided ThreadSleep executor).
• retry_async instructs the tokio runtime to sleep between retries (through the provided TokioSleep executor, requires the async-tokio feature (enabled by default)).

The retry_with_options and retry_async_with_options functions can be used to overwrite the standard behavior with any executor type implementing the DelayExecutor trait.

That way, support for async_std or other asynchronous runtimes could be provided.

MSRV

• As of 0.1.0, the MSRV is 1.56.0
• As of 0.2.0, the MSRV is 1.85.0