broker_tokio/time/
error.rs

1use self::Kind::*;
2use std::error;
3use std::fmt;
4
5/// Errors encountered by the timer implementation.
6///
7/// Currently, there are two different errors that can occur:
8///
9/// * `shutdown` occurs when a timer operation is attempted, but the timer
10///   instance has been dropped. In this case, the operation will never be able
11///   to complete and the `shutdown` error is returned. This is a permanent
12///   error, i.e., once this error is observed, timer operations will never
13///   succeed in the future.
14///
15/// * `at_capacity` occurs when a timer operation is attempted, but the timer
16///   instance is currently handling its maximum number of outstanding delays.
17///   In this case, the operation is not able to be performed at the current
18///   moment, and `at_capacity` is returned. This is a transient error, i.e., at
19///   some point in the future, if the operation is attempted again, it might
20///   succeed. Callers that observe this error should attempt to [shed load]. One
21///   way to do this would be dropping the future that issued the timer operation.
22///
23/// [shed load]: https://en.wikipedia.org/wiki/Load_Shedding
24#[derive(Debug)]
25pub struct Error(Kind);
26
27#[derive(Debug)]
28enum Kind {
29    Shutdown,
30    AtCapacity,
31}
32
33impl Error {
34    /// Create an error representing a shutdown timer.
35    pub fn shutdown() -> Error {
36        Error(Shutdown)
37    }
38
39    /// Returns `true` if the error was caused by the timer being shutdown.
40    pub fn is_shutdown(&self) -> bool {
41        match self.0 {
42            Kind::Shutdown => true,
43            _ => false,
44        }
45    }
46
47    /// Create an error representing a timer at capacity.
48    pub fn at_capacity() -> Error {
49        Error(AtCapacity)
50    }
51
52    /// Returns `true` if the error was caused by the timer being at capacity.
53    pub fn is_at_capacity(&self) -> bool {
54        match self.0 {
55            Kind::AtCapacity => true,
56            _ => false,
57        }
58    }
59}
60
61impl error::Error for Error {}
62
63impl fmt::Display for Error {
64    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
65        use self::Kind::*;
66        let descr = match self.0 {
67            Shutdown => "timer is shutdown",
68            AtCapacity => "timer is at capacity and cannot create a new entry",
69        };
70        write!(fmt, "{}", descr)
71    }
72}
broker_tokio/time/error.rs

broker_tokio/time/
error.rs
