retry_futures.rs

/// Retry a function either until it succeeds, or until it fails `1+retries` times.
fn retry_future<F, T>(retries: usize, mut run: F) -> impl Future<Item=T::Item, Error=T::Error>
    where F: FnMut() -> T,
          T: Future,
{
    futures::future::loop_fn(retries, move |retries| {
        run().map(|t| { futures::future::Loop::Break(t) }).or_else(move |e| {
            futures::future::result(
                if retries == 0 { Err(e) }
                else { Ok(futures::future::Loop::Continue(retries-1)) })
        })
    })
}

/// Perform a GET request, and retry at most `retries` more times if it fails.
fn retry_get(retries: usize, client: &reqwest_async::Client, uri: reqwest::Url)
    -> impl Future<Item=reqwest::async::Response, Error=reqwest::Error> {
    retry_future(retries, {
        let client = client.clone();
        move || { client.get(uri.clone()).send() }
    })
}