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"""
Circuit breaker pattern implementation for external services.
This module provides circuit breaker functionality to prevent cascading
failures and improve system resilience.
"""
import asyncio
from typing import Any, Callable, Optional, Dict, Union
from datetime import datetime, timedelta
from enum import Enum
import time
from dataclasses import dataclass, field
from src.core import get_logger
logger = get_logger(__name__)
class CircuitState(str, Enum):
"""Circuit breaker states."""
CLOSED = "closed" # Normal operation
OPEN = "open" # Circuit is open, rejecting requests
HALF_OPEN = "half_open" # Testing if service is recovered
@dataclass
class CircuitBreakerConfig:
"""Circuit breaker configuration."""
failure_threshold: int = 5 # Failures before opening
recovery_timeout: float = 60.0 # Seconds before trying half-open
success_threshold: int = 3 # Successes to close from half-open
timeout: float = 30.0 # Request timeout
expected_exception: type = Exception # Exception type to count as failure
@dataclass
class CircuitBreakerStats:
"""Circuit breaker statistics."""
total_requests: int = 0
successful_requests: int = 0
failed_requests: int = 0
rejected_requests: int = 0
state_changes: int = 0
last_failure_time: Optional[datetime] = None
last_success_time: Optional[datetime] = None
current_consecutive_failures: int = 0
current_consecutive_successes: int = 0
class CircuitBreakerOpenException(Exception):
"""Exception raised when circuit breaker is open."""
pass
class CircuitBreakerTimeoutException(Exception):
"""Exception raised when request times out."""
pass
class CircuitBreaker:
"""
Circuit breaker implementation for resilient external service calls.
Features:
- Automatic failure detection
- Configurable thresholds
- Recovery mechanism
- Statistics and monitoring
- Async/await support
"""
def __init__(
self,
name: str,
config: Optional[CircuitBreakerConfig] = None
):
"""
Initialize circuit breaker.
Args:
name: Circuit breaker name for identification
config: Configuration parameters
"""
self.name = name
self.config = config or CircuitBreakerConfig()
self.state = CircuitState.CLOSED
self.stats = CircuitBreakerStats()
self._lock = asyncio.Lock()
self._last_failure_time: Optional[float] = None
logger.info(f"Circuit breaker '{name}' initialized")
async def call(self, func: Callable, *args, **kwargs) -> Any:
"""
Execute function with circuit breaker protection.
Args:
func: Function to execute
*args: Function arguments
**kwargs: Function keyword arguments
Returns:
Function result
Raises:
CircuitBreakerOpenException: When circuit is open
CircuitBreakerTimeoutException: When request times out
"""
async with self._lock:
self.stats.total_requests += 1
# Check if circuit should be opened
await self._check_state()
if self.state == CircuitState.OPEN:
self.stats.rejected_requests += 1
raise CircuitBreakerOpenException(
f"Circuit breaker '{self.name}' is open"
)
# Execute the function
start_time = time.time()
try:
# Execute with timeout
result = await asyncio.wait_for(
self._execute_async(func, *args, **kwargs),
timeout=self.config.timeout
)
# Record success
await self._record_success()
execution_time = time.time() - start_time
logger.debug(
f"Circuit breaker '{self.name}' - Success "
f"(time: {execution_time:.3f}s)"
)
return result
except asyncio.TimeoutError:
await self._record_failure()
execution_time = time.time() - start_time
logger.warning(
f"Circuit breaker '{self.name}' - Timeout "
f"(time: {execution_time:.3f}s)"
)
raise CircuitBreakerTimeoutException(
f"Request to '{self.name}' timed out after {self.config.timeout}s"
)
except self.config.expected_exception as e:
await self._record_failure()
execution_time = time.time() - start_time
logger.warning(
f"Circuit breaker '{self.name}' - Failure: {e} "
f"(time: {execution_time:.3f}s)"
)
raise
async def _execute_async(self, func: Callable, *args, **kwargs) -> Any:
"""Execute function, handling both sync and async functions."""
if asyncio.iscoroutinefunction(func):
return await func(*args, **kwargs)
else:
# Run sync function in thread pool
loop = asyncio.get_event_loop()
return await loop.run_in_executor(None, func, *args, **kwargs)
async def _check_state(self):
"""Check and update circuit breaker state."""
current_time = time.time()
if self.state == CircuitState.OPEN:
# Check if we should try half-open
if (self._last_failure_time and
current_time - self._last_failure_time >= self.config.recovery_timeout):
self.state = CircuitState.HALF_OPEN
self.stats.state_changes += 1
logger.info(
f"Circuit breaker '{self.name}' transitioned to HALF_OPEN"
)
elif self.state == CircuitState.HALF_OPEN:
# Half-open state is handled in success/failure recording
pass
async def _record_success(self):
"""Record successful execution."""
async with self._lock:
self.stats.successful_requests += 1
self.stats.current_consecutive_failures = 0
self.stats.current_consecutive_successes += 1
self.stats.last_success_time = datetime.utcnow()
if self.state == CircuitState.HALF_OPEN:
if (self.stats.current_consecutive_successes >=
self.config.success_threshold):
# Transition to closed
self.state = CircuitState.CLOSED
self.stats.state_changes += 1
self.stats.current_consecutive_successes = 0
logger.info(
f"Circuit breaker '{self.name}' transitioned to CLOSED"
)
async def _record_failure(self):
"""Record failed execution."""
async with self._lock:
self.stats.failed_requests += 1
self.stats.current_consecutive_successes = 0
self.stats.current_consecutive_failures += 1
self.stats.last_failure_time = datetime.utcnow()
self._last_failure_time = time.time()
# Check if we should open the circuit
if (self.state in [CircuitState.CLOSED, CircuitState.HALF_OPEN] and
self.stats.current_consecutive_failures >= self.config.failure_threshold):
self.state = CircuitState.OPEN
self.stats.state_changes += 1
logger.warning(
f"Circuit breaker '{self.name}' opened after "
f"{self.stats.current_consecutive_failures} consecutive failures"
)
def get_stats(self) -> Dict[str, Any]:
"""Get circuit breaker statistics."""
success_rate = (
self.stats.successful_requests / self.stats.total_requests
if self.stats.total_requests > 0 else 0
)
return {
"name": self.name,
"state": self.state.value,
"config": {
"failure_threshold": self.config.failure_threshold,
"recovery_timeout": self.config.recovery_timeout,
"success_threshold": self.config.success_threshold,
"timeout": self.config.timeout
},
"stats": {
"total_requests": self.stats.total_requests,
"successful_requests": self.stats.successful_requests,
"failed_requests": self.stats.failed_requests,
"rejected_requests": self.stats.rejected_requests,
"success_rate": success_rate,
"state_changes": self.stats.state_changes,
"current_consecutive_failures": self.stats.current_consecutive_failures,
"current_consecutive_successes": self.stats.current_consecutive_successes,
"last_failure_time": (
self.stats.last_failure_time.isoformat()
if self.stats.last_failure_time else None
),
"last_success_time": (
self.stats.last_success_time.isoformat()
if self.stats.last_success_time else None
)
}
}
async def reset(self):
"""Reset circuit breaker to closed state."""
async with self._lock:
self.state = CircuitState.CLOSED
self.stats.current_consecutive_failures = 0
self.stats.current_consecutive_successes = 0
self._last_failure_time = None
logger.info(f"Circuit breaker '{self.name}' manually reset")
async def force_open(self):
"""Force circuit breaker to open state."""
async with self._lock:
self.state = CircuitState.OPEN
self._last_failure_time = time.time()
logger.warning(f"Circuit breaker '{self.name}' manually opened")
class CircuitBreakerManager:
"""
Manager for multiple circuit breakers.
Provides centralized management and monitoring of circuit breakers.
"""
def __init__(self):
"""Initialize circuit breaker manager."""
self._breakers: Dict[str, CircuitBreaker] = {}
self._default_configs: Dict[str, CircuitBreakerConfig] = {}
def register_default_config(
self,
service_name: str,
config: CircuitBreakerConfig
):
"""
Register default configuration for a service.
Args:
service_name: Service name
config: Default configuration
"""
self._default_configs[service_name] = config
logger.info(f"Registered default config for service '{service_name}'")
def get_circuit_breaker(
self,
service_name: str,
config: Optional[CircuitBreakerConfig] = None
) -> CircuitBreaker:
"""
Get or create circuit breaker for service.
Args:
service_name: Service name
config: Configuration (uses default if not provided)
Returns:
Circuit breaker instance
"""
if service_name not in self._breakers:
# Use provided config or default
breaker_config = (
config or
self._default_configs.get(service_name) or
CircuitBreakerConfig()
)
self._breakers[service_name] = CircuitBreaker(
service_name,
breaker_config
)
return self._breakers[service_name]
async def call_service(
self,
service_name: str,
func: Callable,
*args,
config: Optional[CircuitBreakerConfig] = None,
**kwargs
) -> Any:
"""
Call service through circuit breaker.
Args:
service_name: Service name
func: Function to call
*args: Function arguments
config: Optional configuration
**kwargs: Function keyword arguments
Returns:
Function result
"""
breaker = self.get_circuit_breaker(service_name, config)
return await breaker.call(func, *args, **kwargs)
def get_all_stats(self) -> Dict[str, Any]:
"""Get statistics for all circuit breakers."""
return {
name: breaker.get_stats()
for name, breaker in self._breakers.items()
}
async def reset_all(self):
"""Reset all circuit breakers."""
for breaker in self._breakers.values():
await breaker.reset()
logger.info("All circuit breakers reset")
def get_health_status(self) -> Dict[str, Any]:
"""Get health status of all services."""
healthy_services = []
degraded_services = []
failed_services = []
for name, breaker in self._breakers.items():
if breaker.state == CircuitState.CLOSED:
healthy_services.append(name)
elif breaker.state == CircuitState.HALF_OPEN:
degraded_services.append(name)
else: # OPEN
failed_services.append(name)
total_services = len(self._breakers)
healthy_count = len(healthy_services)
overall_health = "healthy"
if len(failed_services) > 0:
if healthy_count == 0:
overall_health = "critical"
else:
overall_health = "degraded"
elif len(degraded_services) > 0:
overall_health = "degraded"
return {
"overall_health": overall_health,
"total_services": total_services,
"healthy_services": healthy_services,
"degraded_services": degraded_services,
"failed_services": failed_services,
"health_score": healthy_count / total_services if total_services > 0 else 1.0
}
# Global circuit breaker manager
circuit_breaker_manager = CircuitBreakerManager()
# Pre-configured circuit breakers for common services
def setup_default_circuit_breakers():
"""Setup default circuit breaker configurations."""
# Portal da Transparência API
circuit_breaker_manager.register_default_config(
"transparency_api",
CircuitBreakerConfig(
failure_threshold=3,
recovery_timeout=30.0,
success_threshold=2,
timeout=15.0
)
)
# LLM Services (Groq, etc)
circuit_breaker_manager.register_default_config(
"llm_service",
CircuitBreakerConfig(
failure_threshold=5,
recovery_timeout=60.0,
success_threshold=3,
timeout=30.0
)
)
# Database connections
circuit_breaker_manager.register_default_config(
"database",
CircuitBreakerConfig(
failure_threshold=2,
recovery_timeout=10.0,
success_threshold=1,
timeout=5.0
)
)
# Redis connections
circuit_breaker_manager.register_default_config(
"redis",
CircuitBreakerConfig(
failure_threshold=3,
recovery_timeout=20.0,
success_threshold=2,
timeout=3.0
)
)
# Initialize default configurations
setup_default_circuit_breakers()
# Convenience decorators
def circuit_breaker(
service_name: str,
config: Optional[CircuitBreakerConfig] = None
):
"""
Decorator to protect functions with circuit breaker.
Args:
service_name: Service name for circuit breaker
config: Optional configuration
"""
def decorator(func):
async def wrapper(*args, **kwargs):
return await circuit_breaker_manager.call_service(
service_name, func, *args, config=config, **kwargs
)
return wrapper
return decorator
# Example usage functions
async def protected_api_call(url: str) -> dict:
"""Example of API call protected by circuit breaker."""
import httpx
async def make_request():
async with httpx.AsyncClient() as client:
response = await client.get(url)
response.raise_for_status()
return response.json()
return await circuit_breaker_manager.call_service(
"external_api",
make_request
) |