# Requirements Document: Operational Resilience and Error Handling

## Introduction

This feature addresses critical operational gaps in the beast-dream-snow-loader project. While the MVP successfully implements core data transformation and loading functionality, it lacks comprehensive error handling, monitoring, logging, and operational resilience needed for production use. This spec defines requirements to transform the project from a functional MVP into a production-ready system.

## Glossary

- **System**: The beast-dream-snow-loader application
- **ServiceNow_API**: ServiceNow REST API endpoints
- **UniFi_API**: UniFi Dream Machine API (via beast-unifi-integration)
- **Error_Context**: Structured information about failures including operation, data, and environment
- **Retry_Policy**: Configurable rules for automatic retry attempts
- **Circuit_Breaker**: Pattern to prevent cascading failures by temporarily stopping requests
- **Health_Check**: Automated verification of system and dependency status
- **Audit_Trail**: Comprehensive log of all operations and their outcomes
- **Graceful_Degradation**: System behavior that maintains partial functionality during failures

## Requirements

### Requirement 1

**User Story:** As a system administrator, I want comprehensive error handling and logging, so that I can diagnose and resolve issues quickly.

#### Acceptance Criteria

1. WHEN any operation fails, THE System SHALL capture detailed error context including operation type, input data, timestamp, and stack trace
2. WHEN errors occur, THE System SHALL log structured error information to both console and persistent storage
3. WHEN ServiceNow_API returns error responses, THE System SHALL parse and expose specific error details from ServiceNow
4. WHEN authentication fails, THE System SHALL provide clear guidance on credential configuration and validation
5. WHERE error patterns emerge, THE System SHALL aggregate and report common failure modes

### Requirement 2

**User Story:** As a DevOps engineer, I want automatic retry and circuit breaker functionality, so that temporary failures don't cause complete system outages.

#### Acceptance Criteria

1. WHEN ServiceNow_API requests fail with transient errors, THE System SHALL implement exponential backoff retry logic
2. WHEN rate limits are encountered, THE System SHALL respect rate limit headers and implement appropriate delays
3. IF consecutive failures exceed threshold, THEN THE System SHALL activate circuit breaker to prevent cascading failures
4. WHILE circuit breaker is active, THE System SHALL periodically test service availability for recovery
5. WHERE network timeouts occur, THE System SHALL implement configurable timeout policies with progressive backoff

### Requirement 3

**User Story:** As a data engineer, I want comprehensive data validation and integrity checks, so that corrupted or invalid data doesn't enter ServiceNow.

#### Acceptance Criteria

1. WHEN transforming UniFi data, THE System SHALL validate all required fields are present and properly formatted
2. WHEN loading data to ServiceNow, THE System SHALL verify data integrity before and after operations
3. IF data validation fails, THEN THE System SHALL provide detailed field-level error information
4. WHEN relationships are created, THE System SHALL verify referenced records exist before linking
5. WHERE data inconsistencies are detected, THE System SHALL provide rollback capabilities

### Requirement 4

**User Story:** As a monitoring engineer, I want health checks and metrics collection, so that I can proactively identify and address system issues.

#### Acceptance Criteria

1. THE System SHALL provide health check endpoints that verify connectivity to all dependencies
2. WHEN operations complete, THE System SHALL collect and expose performance metrics including duration and success rates
3. WHEN system resources are constrained, THE System SHALL monitor and report memory and CPU usage
4. WHERE performance degrades, THE System SHALL provide alerts and diagnostic information
5. THE System SHALL expose metrics in standard formats compatible with monitoring systems

### Requirement 5

**User Story:** As a security administrator, I want secure credential management following beast principles, so that I can maintain security compliance and investigate issues.

#### Acceptance Criteria

1. WHEN credentials are accessed, THE System SHALL use 1Password CLI as canonical source with environment variable fallback
2. WHEN operations modify ServiceNow data, THE System SHALL create comprehensive Audit_Trail entries
3. IF credential validation fails, THEN THE System SHALL provide secure error messages without credential exposure
4. WHEN 1Password integration is used, THE System SHALL verify CLI availability and authentication status following beast credential patterns
5. THE System SHALL never hardcode credentials and SHALL follow the canonical source principle where 1Password is source of truth

### Requirement 6

**User Story:** As a system operator, I want graceful degradation and partial failure handling, so that the system remains functional even when some components fail.

#### Acceptance Criteria

1. WHEN ServiceNow tables are unavailable, THE System SHALL fall back to base cmdb_ci table operations
2. WHEN batch operations partially fail, THE System SHALL continue processing remaining items and report partial success
3. IF UniFi_API is temporarily unavailable, THEN THE System SHALL cache last known good data and continue with stale data warnings
4. WHEN plugin dependencies are missing, THE System SHALL provide Graceful_Degradation with reduced functionality
5. WHERE critical services are down, THE System SHALL maintain read-only operations and queue writes for later processing

### Requirement 7

**User Story:** As a developer, I want comprehensive configuration management following beast quality standards, so that the system adapts appropriately to different deployment contexts.

#### Acceptance Criteria

1. THE System SHALL detect execution environment and adapt behavior accordingly (development, staging, production)
2. WHEN configuration is invalid or missing, THE System SHALL provide clear guidance on required settings with beast-compliant error messages
3. WHEN running in different environments, THE System SHALL apply appropriate structured logging levels and output formats
4. WHERE environment-specific behaviors are needed, THE System SHALL support configuration overrides while maintaining quality gates
5. THE System SHALL validate all configuration at startup and fail fast with clear error messages following beast principles

### Requirement 8

**User Story:** As a data analyst, I want comprehensive operation reporting and statistics with postmortem-ready logging, so that I can understand system performance and data quality.

#### Acceptance Criteria

1. WHEN operations complete, THE System SHALL generate detailed reports including record counts, success rates, and timing
2. WHEN data quality issues are detected, THE System SHALL report specific problems with affected records using structured logging
3. WHEN relationships are processed, THE System SHALL report linking success rates and orphaned records
4. WHERE performance bottlenecks exist, THE System SHALL identify slow operations and suggest optimizations
5. THE System SHALL maintain postmortem-ready logs with key events for LLM analysis and historical trend analysis

### Requirement 9

**User Story:** As a maintainer agent, I want the system to follow beast project patterns and quality standards, so that it integrates properly with the beast ecosystem.

#### Acceptance Criteria

1. THE System SHALL follow beast naming conventions and repository patterns (nkllon/beast-* structure)
2. WHEN publishing to PyPI, THE System SHALL maintain SonarCloud integration and quality gates
3. WHEN implementing error handling, THE System SHALL use structured logging appropriate for Python projects
4. WHERE quality checks are performed, THE System SHALL never bypass quality gates (no --no-verify patterns)
5. THE System SHALL maintain agent guidance documentation and follow principle-level architectural decisions