| use self::Kind::*; |
| |
| use std::error; |
| use std::fmt; |
| |
| /// Errors encountered by the timer implementation. |
| /// |
| /// Currently, there are two different errors that can occur: |
| /// |
| /// * `shutdown` occurs when a timer operation is attempted, but the timer |
| /// instance has been dropped. In this case, the operation will never be able |
| /// to complete and the `shutdown` error is returned. This is a permanent |
| /// error, i.e., once this error is observed, timer operations will never |
| /// succeed in the future. |
| /// |
| /// * `at_capacity` occurs when a timer operation is attempted, but the timer |
| /// instance is currently handling its maximum number of outstanding delays. |
| /// In this case, the operation is not able to be performed at the current |
| /// moment, and `at_capacity` is returned. This is a transient error, i.e., at |
| /// some point in the future, if the operation is attempted again, it might |
| /// succeed. Callers that observe this error should attempt to [shed load]. One |
| /// way to do this would be dropping the future that issued the timer operation. |
| /// |
| /// [shed load]: https://en.wikipedia.org/wiki/Load_Shedding |
| #[derive(Debug)] |
| pub struct Error(Kind); |
| |
| #[derive(Debug)] |
| enum Kind { |
| Shutdown, |
| AtCapacity, |
| } |
| |
| impl Error { |
| /// Create an error representing a shutdown timer. |
| pub fn shutdown() -> Error { |
| Error(Shutdown) |
| } |
| |
| /// Returns `true` if the error was caused by the timer being shutdown. |
| pub fn is_shutdown(&self) -> bool { |
| match self.0 { |
| Kind::Shutdown => true, |
| _ => false, |
| } |
| } |
| |
| /// Create an error representing a timer at capacity. |
| pub fn at_capacity() -> Error { |
| Error(AtCapacity) |
| } |
| |
| /// Returns `true` if the error was caused by the timer being at capacity. |
| pub fn is_at_capacity(&self) -> bool { |
| match self.0 { |
| Kind::AtCapacity => true, |
| _ => false, |
| } |
| } |
| } |
| |
| impl error::Error for Error { |
| fn description(&self) -> &str { |
| use self::Kind::*; |
| |
| match self.0 { |
| Shutdown => "timer is shutdown", |
| AtCapacity => "timer is at capacity and cannot create a new entry", |
| } |
| } |
| } |
| |
| impl fmt::Display for Error { |
| fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result { |
| use std::error::Error; |
| self.description().fmt(fmt) |
| } |
| } |