bendns' repos / rust-fsm
Finite state machines in rust; bendns fork to add types.
Diffstat (limited to 'rust_fsm/examples/circuit_breaker.rs')
-rw-r--r--rust_fsm/examples/circuit_breaker.rs104
1 files changed, 104 insertions, 0 deletions
diff --git a/rust_fsm/examples/circuit_breaker.rs b/rust_fsm/examples/circuit_breaker.rs
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+/// A dummy implementation of the Circuit Breaker pattern to demonstrate
+/// capabilities of this library.
+/// https://martinfowler.com/bliki/CircuitBreaker.html
+use rust_fsm::*;
+use std::sync::{Arc, Mutex};
+
+#[derive(Debug)]
+enum CircuitBreakerInput {
+ Successful,
+ Unsuccessful,
+ TimerTriggered,
+}
+
+#[derive(Debug, PartialEq)]
+enum CircuitBreakerState {
+ Closed,
+ Open,
+ HalfOpen,
+}
+
+#[derive(Debug, PartialEq)]
+struct CircuitBreakerOutputSetTimer;
+
+#[derive(Debug)]
+struct CircuitBreakerMachine;
+
+impl StateMachine for CircuitBreakerMachine {
+ type Input = CircuitBreakerInput;
+ type State = CircuitBreakerState;
+ type Output = CircuitBreakerOutputSetTimer;
+ const INITIAL_STATE: Self::State = CircuitBreakerState::Closed;
+
+ fn transition(state: &Self::State, input: &Self::Input) -> Option<Self::State> {
+ match (state, input) {
+ (CircuitBreakerState::Closed, CircuitBreakerInput::Unsuccessful) => {
+ Some(CircuitBreakerState::Open)
+ }
+ (CircuitBreakerState::Open, CircuitBreakerInput::TimerTriggered) => {
+ Some(CircuitBreakerState::HalfOpen)
+ }
+ (CircuitBreakerState::HalfOpen, CircuitBreakerInput::Successful) => {
+ Some(CircuitBreakerState::Closed)
+ }
+ (CircuitBreakerState::HalfOpen, CircuitBreakerInput::Unsuccessful) => {
+ Some(CircuitBreakerState::Open)
+ }
+ _ => None,
+ }
+ }
+
+ fn output(state: &Self::State, input: &Self::Input) -> Option<Self::Output> {
+ match (state, input) {
+ (CircuitBreakerState::Closed, CircuitBreakerInput::Unsuccessful) => {
+ Some(CircuitBreakerOutputSetTimer)
+ }
+ (CircuitBreakerState::HalfOpen, CircuitBreakerInput::Unsuccessful) => {
+ Some(CircuitBreakerOutputSetTimer)
+ }
+ _ => None,
+ }
+ }
+}
+
+fn main() {
+ let machine: StateMachineWrapper<CircuitBreakerMachine> = StateMachineWrapper::new();
+
+ // Unsuccessful request
+ let machine = Arc::new(Mutex::new(machine));
+ {
+ let mut lock = machine.lock().unwrap();
+ let res = lock.consume_anyway(&CircuitBreakerInput::Unsuccessful);
+ assert_eq!(res, Some(CircuitBreakerOutputSetTimer));
+ assert_eq!(lock.state(), &CircuitBreakerState::Open);
+ }
+
+ // Set up a timer
+ let machine_wait = machine.clone();
+ std::thread::spawn(move || {
+ std::thread::sleep_ms(5000);
+ let mut lock = machine_wait.lock().unwrap();
+ let res = lock.consume_anyway(&CircuitBreakerInput::TimerTriggered);
+ assert_eq!(res, None);
+ assert_eq!(lock.state(), &CircuitBreakerState::HalfOpen);
+ });
+
+ // Try to pass a request when the circuit breaker is still open
+ let machine_try = machine.clone();
+ std::thread::spawn(move || {
+ std::thread::sleep_ms(1000);
+ let mut lock = machine_try.lock().unwrap();
+ let res = lock.consume_anyway(&CircuitBreakerInput::Successful);
+ assert_eq!(res, None);
+ assert_eq!(lock.state(), &CircuitBreakerState::Open);
+ });
+
+ // Test if the circit breaker was actually closed
+ std::thread::sleep_ms(7000);
+ {
+ let mut lock = machine.lock().unwrap();
+ let res = lock.consume_anyway(&CircuitBreakerInput::Successful);
+ assert_eq!(res, None);
+ assert_eq!(lock.state(), &CircuitBreakerState::Closed);
+ }
+}