retry

Runs operation until it succeeds, at most attempts times, and returns the first success or the last error.

operation receives the number of the attempt, starting at 1, so it can wait before a retry (for instance with backoff) or log it: this helper never sleeps, so it works the same in a test as in production. attempts of 0 is treated as 1: an operation is always tried once.

Import

use helpers4::function::retry;

Cargo feature function (enabled by default). To compile only this module:

cargo add helpers4 --no-default-features --features function

or in Cargo.toml:

[dependencies]
helpers4 = { version = "0.0.6", default-features = false, features = ["function"] }

Signature

pub fn retry<T, E>(attempts: u32, mut operation: impl FnMut(u32) -> Result<T, E>) -> Result<T, E>

Parameters

Parameter	Type	Description
attempts	u32	The most times to run operation.
operation	impl FnMut(u32) -> Result<T, E>	The work to try, given the attempt number.

Returns

Result<T, E> — Ok on success, otherwise an Err: see Errors.

Errors

The error of the last attempt, when every attempt failed.

Examples

use helpers4::function::retry;

let result = retry(3, |attempt| if attempt < 3 { Err("not yet") } else { Ok(attempt) });
assert_eq!(result, Ok(3));

let failed: Result<u32, &str> = retry(2, |_| Err("always"));
assert_eq!(failed, Err("always"));

Source

src/function/retry.rs