Function retry::retry [−] [src]

pub fn retry<F, G, R>(tries: usize, wait: u32, value_fn: F, condition_fn: G) -> Result<R, RetryError> where F: FnMut() -> R, G: FnMut(&R) -> bool

Invokes a function until a condition is satisfied.

value_fn is a closure that will be executed to produce a value. condition_fn is a closure that takes the value produced by value_fn and returns a boolean indicating whether or not some desired condition is true. retry will invoke value_fn up to tries times, returning the value as soon as condition_fn is satisfied, or returning an error when the last try was unsuccessful. It will wait wait milliseconds after each unsuccessful try.

Failures

Will fail when:

  1. value_fn has been been invoked tries times and has still not satisfied condition_fn.
  2. tries is zero. It must be at least 1.

Examples

Imagine an HTTP API with an endpoint that returns 204 No Content while a job is processing, and eventually 200 OK when the job has completed. Retrying until the job is finished would be written:

match retry(10, 500, || api_client.query_job_status(), |response| response.code == 200) {
    Ok(response) => println!("Job completed with result: {}", response.body),
    Err(error) => println!("Job completion could not be verified: {}", error),
}

This retries the API call up to 10 times, waiting 500 milliseconds after each unsuccesful attempt.