FLY-ISOLATE: Implement failure isolation to prevent cascade failures

Labels: enhancement, fly-methodology, reliability

Description

The mock data incident showed how one bad pattern (fallback to mocks) can cascade through multiple layers. We need isolation mechanisms to contain failures.

Problem

• Mock fallbacks hid real failures
• Agents validated mock data as success
• Failure cascaded through validation layers
• No circuit breakers to stop propagation

Solution

• Clear service boundaries
• Explicit failure modes
• Circuit breakers for integrations
• Fail-fast with clear errors

Implementation

• Define service boundary patterns
• Create integration circuit breakers
• Implement health checks for each service
• Add failure isolation to gameplan template
• Document in methodology

Success Metrics

• Zero cascade failures
• 100% of failures isolated to originating service
• Clear error messages at each boundary
• No mock data or theater validation

Estimated: 6 hours Priority: High (prevents future incidents)

Technical Implementation

Service Boundaries

• API Layer: FastAPI endpoints with clear error responses
• Service Layer: Business logic with explicit failure modes
• Integration Layer: External APIs with circuit breakers
• Data Layer: Database operations with transaction boundaries

Circuit Breaker Pattern

class IntegrationCircuitBreaker:
    def __init__(self, failure_threshold=5, timeout=60):
        self.failure_count = 0
        self.failure_threshold = failure_threshold
        self.timeout = timeout
        self.last_failure_time = None
        self.state = "CLOSED"  # CLOSED, OPEN, HALF_OPEN

Health Check Endpoints

• /health/github - GitHub API connectivity
• /health/calendar - Google Calendar API status
• /health/database - Database connection status
• /health/overall - System-wide health status

Failure Isolation Rules

1. No Silent Failures: All failures must be logged and reported
2. No Mock Fallbacks: Replace with honest error messages
3. Clear Boundaries: Each service has defined responsibilities
4. Fail Fast: Stop processing when critical dependencies fail
5. User Transparency: Show real status, not fake success

Integration Points

• Gameplan template updates
• Agent prompt templates
• Service architecture documentation
• Testing methodology updates