Trait Backoff 

pub trait Backoff:
    Iterator<Item = Duration>
    + Send
    + Sync
    + Unpin { }

导出 backon 实现失败重试 Backoff is an Iterator that returns Duration.

• Some(Duration) indicates the caller should sleep(Duration) and retry the request.
• None indicates the limits have been reached, and the caller should return the current error instead.

Implementors

impl<T> Backoff for T

where T: Iterator<Item = Duration> + Send + Sync + Unpin,