How to Mock a Circuit Breaker Reset Timeout in Python

import time
import random


class CircuitBreaker:
    def __init__(self, failure_threshold=3, reset_timeout=5):
        self.failure_threshold = failure_threshold
        self.reset_timeout = reset_timeout
        self.failure_count = 0
        self.last_failure_time = None
        self.state = "CLOSED"  # CLOSED (normal), OPEN (tripped), HALF_OPEN (testing)

    def call(self, func):
        if self.state == "OPEN":
            if time.time() - self.last_failure_time >= self.reset_timeout:
                self.state = "HALF_OPEN"
                print("Circuit half-open: testing one request")
            else:
                print("Circuit OPEN: request rejected immediately")
                raise Exception("Circuit breaker is open")

        try:
            result = func()
            if self.state == "HALF_OPEN":
                self.state = "CLOSED"
                self.failure_count = 0
                print("Circuit closed after successful half-open test")
            else:
                self.failure_count = 0
            return result
        except Exception as e:
            self.failure_count += 1
            self.last_failure_time = time.time()
            if self.failure_count >= self.failure_threshold:
                self.state = "OPEN"
                print(f"Circuit OPEN after {self.failure_count} failures")
            raise e


# Simulated flaky service
def flaky_service():
    if random.random() < 0.6:
        raise ConnectionError("Service unavailable")
    return "Success"


if __name__ == "__main__":
    breaker = CircuitBreaker()
    for attempt in range(10):
        try:
            result = breaker.call(flaky_service)
            print(f"Attempt {attempt + 1}: {result}")
        except Exception as e:
            print(f"Attempt {attempt + 1}: FAILED ({e})")
        time.sleep(1.5)

    print(f"Final state: {breaker.state}")