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use super::error::Error;
use super::failure_policy::FailurePolicy;
use super::failure_predicate::{self, FailurePredicate};
use super::instrument::Instrument;
use super::state_machine::StateMachine;
pub trait CircuitBreaker {
fn is_call_permitted(&self) -> bool;
#[inline]
fn call<F, E, R>(&self, f: F) -> Result<R, Error<E>>
where
F: FnOnce() -> Result<R, E>,
{
self.call_with(failure_predicate::Any, f)
}
fn call_with<P, F, E, R>(&self, predicate: P, f: F) -> Result<R, Error<E>>
where
P: FailurePredicate<E>,
F: FnOnce() -> Result<R, E>;
}
impl<POLICY, INSTRUMENT> CircuitBreaker for StateMachine<POLICY, INSTRUMENT>
where
POLICY: FailurePolicy,
INSTRUMENT: Instrument,
{
#[inline]
fn is_call_permitted(&self) -> bool {
self.is_call_permitted()
}
fn call_with<P, F, E, R>(&self, predicate: P, f: F) -> Result<R, Error<E>>
where
P: FailurePredicate<E>,
F: FnOnce() -> Result<R, E>,
{
if !self.is_call_permitted() {
return Err(Error::Rejected);
}
match f() {
Ok(ok) => {
self.on_success();
Ok(ok)
}
Err(err) => {
if predicate.is_err(&err) {
self.on_error();
} else {
self.on_success();
}
Err(Error::Inner(err))
}
}
}
}
#[cfg(test)]
mod tests {
use std::time::Duration;
use super::super::backoff;
use super::super::config::Config;
use super::super::failure_policy::consecutive_failures;
use super::*;
#[test]
fn call_with() {
let circuit_breaker = new_circuit_breaker();
let is_err = |err: &bool| !(*err);
for _ in 0..2 {
match circuit_breaker.call_with(is_err, || Err::<(), _>(true)) {
Err(Error::Inner(true)) => {}
x => unreachable!("{:?}", x),
}
assert_eq!(true, circuit_breaker.is_call_permitted());
}
match circuit_breaker.call_with(is_err, || Err::<(), _>(false)) {
Err(Error::Inner(false)) => {}
x => unreachable!("{:?}", x),
}
assert_eq!(false, circuit_breaker.is_call_permitted());
}
#[test]
fn call_ok() {
let circuit_breaker = new_circuit_breaker();
circuit_breaker.call(|| Ok::<_, ()>(())).unwrap();
assert_eq!(true, circuit_breaker.is_call_permitted());
}
#[test]
fn call_err() {
let circuit_breaker = new_circuit_breaker();
match circuit_breaker.call(|| Err::<(), _>(())) {
Err(Error::Inner(())) => {}
x => unreachable!("{:?}", x),
}
assert_eq!(false, circuit_breaker.is_call_permitted());
match circuit_breaker.call(|| Err::<(), _>(())) {
Err(Error::Rejected) => {}
x => unreachable!("{:?}", x),
}
assert_eq!(false, circuit_breaker.is_call_permitted());
}
fn new_circuit_breaker() -> impl CircuitBreaker {
let backoff = backoff::constant(Duration::from_secs(5));
let policy = consecutive_failures(1, backoff);
Config::new().failure_policy(policy).build()
}
}