Circuit Breakers and Retry Logic

Circuit Breaker Pattern

class CircuitBreaker:
    def __init__(self, threshold: int = 5, timeout: float = 60.0):
        self.threshold = threshold
        self.timeout = timeout
        self.failures = 0
        self.last_failure = 0.0
        self.state = 'closed'

    def call(self, fn, *args, **kwargs):
        if self.state == 'open':
            if time.time() - self.last_failure > self.timeout:
                self.state = 'half_open'
            else:
                raise Exception('circuit open')
        try:
            result = fn(*args, **kwargs)
            self._on_success()
            return result
        except Exception as e:
            self._on_failure()
            raise e

    def _on_success(self):
        self.failures = 0
        self.state = 'closed'

    def _on_failure(self):
        self.failures += 1
        self.last_failure = time.time()
        if self.failures >= self.threshold:
            self.state = 'open'

Exponential Backoff Retry

import time
import random

def retry_with_backoff(fn, max_retries=5):
    for attempt in range(max_retries):
        try:
            return fn()
        except Exception:
            if attempt == max_retries - 1:
                raise
            sleep = (2 ** attempt) + random.random()
            time.sleep(sleep)