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python.resilience.missing_circuit_breaker

Stability High

Detects HTTP client calls to external services without circuit breaker protection, which can cause cascading failures.

Why It Matters

Without circuit breakers, a failing dependency can:

Cause cascading failures — Slow downstream services cause your service to slow down
Exhaust resources — Threads/connections pile up waiting for unresponsive services
Extend outages — Continuous retries prevent the failing service from recovering
Affect all users — One bad dependency impacts all requests

Circuit breakers “trip” after consecutive failures, failing fast without hitting the troubled service.

Example

# ❌ Before (no circuit breaker)
def fetch_data():
    return requests.get('https://api.example.com/data', timeout=30)

# ✅ After (with circuit breaker)
from circuitbreaker import circuit

@circuit(failure_threshold=5, recovery_timeout=60)
def fetch_data():
    # After 5 consecutive failures, circuit opens for 60 seconds
    # During this time, calls fail fast without hitting the external service
    return requests.get('https://api.example.com/data', timeout=30)

What Unfault Detects

HTTP calls (requests, httpx, aiohttp) without circuit breaker decorators
gRPC client calls without circuit protection
External service integrations without failure isolation

Auto-Fix

Unfault generates patches that add circuit breaker decorators using the circuitbreaker library:

from circuitbreaker import circuit

@circuit(failure_threshold=5, recovery_timeout=60)
def fetch_external_data():
    response = requests.get('https://api.example.com/data', timeout=30)
    return response.json()

Configuration Options

# Using pybreaker for more control
from pybreaker import CircuitBreaker, CircuitBreakerListener

class LoggingListener(CircuitBreakerListener):
    def state_change(self, cb, old_state, new_state):
        logger.warning(f"Circuit {cb.name}: {old_state} -> {new_state}")

breaker = CircuitBreaker(
    fail_max=5,
    reset_timeout=60,
    listeners=[LoggingListener()]
)

@breaker
def fetch_data():
    return requests.get('https://api.example.com/data', timeout=30)