bendns' repos / rust-fsm
Finite state machines in rust; bendns fork to add types.
Diffstat (limited to 'examples/circuit_breaker_dsl.rs')
-rw-r--r--examples/circuit_breaker_dsl.rs59
1 files changed, 59 insertions, 0 deletions
diff --git a/examples/circuit_breaker_dsl.rs b/examples/circuit_breaker_dsl.rs
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+/// A dummy implementation of the Circuit Breaker pattern to demonstrate
+/// capabilities of its library DSL for defining finite state machines.
+/// https://martinfowler.com/bliki/CircuitBreaker.html
+use rust_fsm::*;
+use std::sync::{Arc, Mutex};
+use std::time::Duration;
+
+state_machine! {
+ CircuitBreaker(Closed)
+
+ Closed(Unsuccessful) => Open [SetupTimer],
+ Open(TimerTriggered) => HalfOpen,
+ HalfOpen => {
+ Successful => Closed,
+ Unsuccessful => Open [SetupTimer]
+ }
+}
+
+fn main() {
+ let machine: StateMachine<CircuitBreaker> = StateMachine::new();
+
+ // Unsuccessful request
+ let machine = Arc::new(Mutex::new(machine));
+ {
+ let mut lock = machine.lock().unwrap();
+ let res = lock.consume(&CircuitBreakerInput::Unsuccessful).unwrap();
+ assert_eq!(res, Some(CircuitBreakerOutput::SetupTimer));
+ assert_eq!(lock.state(), &CircuitBreakerState::Open);
+ }
+
+ // Set up a timer
+ let machine_wait = machine.clone();
+ std::thread::spawn(move || {
+ std::thread::sleep(Duration::new(5, 0));
+ let mut lock = machine_wait.lock().unwrap();
+ let res = lock.consume(&CircuitBreakerInput::TimerTriggered).unwrap();
+ 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(Duration::new(1, 0));
+ let mut lock = machine_try.lock().unwrap();
+ let res = lock.consume(&CircuitBreakerInput::Successful);
+ assert_eq!(res, Err(()));
+ assert_eq!(lock.state(), &CircuitBreakerState::Open);
+ });
+
+ // Test if the circit breaker was actually closed
+ std::thread::sleep(Duration::new(7, 0));
+ {
+ let mut lock = machine.lock().unwrap();
+ let res = lock.consume(&CircuitBreakerInput::Successful).unwrap();
+ assert_eq!(res, None);
+ assert_eq!(lock.state(), &CircuitBreakerState::Closed);
+ }
+}