circuit_breaker.py

import time
import threading

class CircuitBreaker:
    def __init__(self, failure_threshold=5, recovery_timeout=30, expected_exception=Exception):
        
        self.failure_threshold = failure_threshold          
        self.recovery_timeout = recovery_timeout            
        self.expected_exception = expected_exception       
        self.failure_count = 0                              
        self.last_failure_time = None                       
        self.state = 'CLOSED'                               
        self.lock = threading.Lock()                        

    def call(self, func, *args, **kwargs):
       
        with self.lock:  
            if self.state == 'OPEN':
                
                time_since_failure = time.time() - self.last_failure_time
                if time_since_failure > self.recovery_timeout:
                    
                    self.state = 'HALF_OPEN'
                else:
                    
                    raise CircuitBreakerOpenException("Circuit is open. Call denied.")
            
            try:
                
                result = func(*args, **kwargs)
            except self.expected_exception as e:
                
                self.failure_count += 1
                self.last_failure_time = time.time()  
                if self.failure_count >= self.failure_threshold:
                    
                    self.state = 'OPEN'
                raise e 
            else:
                
                if self.state == 'HALF_OPEN':
                  
                    self.state = 'CLOSED'
                    self.failure_count = 0 
                return result  

class CircuitBreakerOpenException(Exception):
    """Custom exception raised when the circuit breaker is open."""
    pass