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use std::time::Duration;
use crate::BoxProcessor;
/// Configuration for the circuit breaker pattern.
///
/// The circuit breaker monitors failures and temporarily stops sending
/// requests to a failing service, giving it time to recover.
///
/// # States
///
/// - **Closed** — Normal operation. Failures are counted; when `failure_threshold`
/// consecutive failures occur, the circuit opens.
/// - **Open** — All calls are rejected with [`CamelError::CircuitOpen`](crate::CamelError::CircuitOpen).
/// After `open_duration` elapses, the circuit transitions to half-open.
/// - **Half-Open** — A single probe call is allowed through. If it succeeds
/// (`success_threshold` times), the circuit closes. If it fails, the circuit reopens.
#[derive(Clone)]
pub struct CircuitBreakerConfig {
/// Number of consecutive failures before opening the circuit.
pub failure_threshold: u32,
/// Number of successful probes in half-open state before closing.
///
/// **Current limitation:** Only `1` is effectively supported. The state
/// machine resets to `Closed` on the first successful half-open probe
/// regardless of this value. Multi-probe half-open tracking is deferred.
pub success_threshold: u32,
/// How long the circuit stays open before allowing a probe.
pub open_duration: Duration,
/// Optional fallback processor invoked when circuit is open.
pub fallback: Option<BoxProcessor>,
}
impl std::fmt::Debug for CircuitBreakerConfig {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
f.debug_struct("CircuitBreakerConfig")
.field("failure_threshold", &self.failure_threshold)
.field("success_threshold", &self.success_threshold)
.field("open_duration", &self.open_duration)
.field("fallback", &self.fallback.as_ref().map(|_| "<processor>"))
.finish()
}
}
impl Default for CircuitBreakerConfig {
fn default() -> Self {
Self {
failure_threshold: 5,
success_threshold: 1,
open_duration: Duration::from_secs(30),
fallback: None,
}
}
}
impl CircuitBreakerConfig {
pub fn new() -> Self {
Self::default()
}
pub fn failure_threshold(mut self, n: u32) -> Self {
self.failure_threshold = n;
self
}
pub fn open_duration(mut self, duration: Duration) -> Self {
self.open_duration = duration;
self
}
pub fn fallback(mut self, fallback: BoxProcessor) -> Self {
self.fallback = Some(fallback);
self
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_default_config() {
let config = CircuitBreakerConfig::default();
assert_eq!(config.failure_threshold, 5);
assert_eq!(config.success_threshold, 1);
assert_eq!(config.open_duration, Duration::from_secs(30));
assert!(config.fallback.is_none());
}
#[test]
fn test_builder_pattern() {
let config = CircuitBreakerConfig::new()
.failure_threshold(3)
.open_duration(Duration::from_millis(500));
assert_eq!(config.failure_threshold, 3);
assert_eq!(config.success_threshold, 1); // default, no setter exposed
assert_eq!(config.open_duration, Duration::from_millis(500));
}
}