Phase 2 Step 7: Implement Error Handling & Logging

Comprehensive error handling and logging system with production-ready
features for monitoring, debugging, and user experience.

Enhanced Logging System:
- Implemented RotatingFileHandler (10MB per file, 10 backups, 100MB total)
- Separate error log file for ERROR level messages with detailed tracebacks
- Structured logging with request IDs, timestamps, and module names
- RequestIDLogFilter for automatic request context injection
- Console logging in debug mode with simplified format

Request/Response Middleware:
- Request ID generation using UUID (8-character prefix for readability)
- Request timing with millisecond precision
- User authentication context in all logs
- Response duration tracking and headers (X-Request-ID, X-Request-Duration-Ms)
- Security headers: X-Content-Type-Options, X-Frame-Options, X-XSS-Protection

Database Error Handling:
- Enabled SQLite WAL mode for better concurrency with background jobs
- Busy timeout configuration (15 seconds) for lock handling
- Automatic rollback on request exceptions via teardown handler
- Dedicated SQLAlchemyError handler with explicit rollback
- Connection pooling with pre-ping validation

Comprehensive Error Handlers:
- Content negotiation: JSON responses for API, HTML for web requests
- Error handlers for 400, 401, 403, 404, 405, 500
- Database rollback in all error handlers
- Full exception logging with traceback for debugging

Custom Error Templates:
- Created web/templates/errors/ directory with 6 templates
- Dark theme matching application design (slate colors)
- User-friendly error messages with navigation
- Templates: 400, 401, 403, 404, 405, 500

Testing:
- Comprehensive test suite (320+ lines) in tests/test_error_handling.py
- Tests for JSON vs HTML error responses
- Request ID and duration header verification
- Security header validation
- Log rotation configuration tests
- Structured logging tests

Bug Fix:
- Fixed pagination bug in scans API endpoint
- Changed paginated_result.total_pages to paginated_result.pages
- Resolves AttributeError when listing scans

Files Added:
- tests/test_error_handling.py
- web/templates/errors/400.html
- web/templates/errors/401.html
- web/templates/errors/403.html
- web/templates/errors/404.html
- web/templates/errors/405.html
- web/templates/errors/500.html

Files Modified:
- web/app.py (logging, error handlers, request handlers, database config)
- web/api/scans.py (pagination bug fix)
- docs/ai/PHASE2.md (mark Step 7 complete, update progress to 86%)

Phase 2 Progress: 12/14 days complete (86%)

docs/ai/PHASE2.md

@@ -1,7 +1,7 @@
 # Phase 2 Implementation Plan: Flask Web App Core
 
-**Status:** Step 6 Complete ✅ - Docker & Deployment (Day 11)
-**Progress:** 11/14 days complete (79%)
+**Status:** Step 7 Complete ✅ - Error Handling & Logging (Day 12)
+**Progress:** 12/14 days complete (86%)
 **Estimated Duration:** 14 days (2 weeks)
 **Dependencies:** Phase 1 Complete ✅
 
@@ -52,8 +52,16 @@
   - Verified Dockerfile is production-ready
   - Created comprehensive DEPLOYMENT.md documentation
   - Deployment workflow validated
-- 📋 **Step 7: Error Handling & Logging** (Day 12) - NEXT
-- 📋 **Step 8: Testing & Documentation** (Days 13-14) - Pending
+- ✅ **Step 7: Error Handling & Logging** (Day 12) - COMPLETE
+  - Enhanced logging with rotation (10MB per file, 10 backups)
+  - Structured logging with request IDs and timing
+  - Request/response logging middleware with duration tracking
+  - Database error handling with automatic rollback
+  - Custom error templates for 400, 401, 403, 404, 405, 500
+  - Content negotiation (JSON for API, HTML for web)
+  - SQLite WAL mode for better concurrency
+  - Comprehensive error handling tests
+- 📋 **Step 8: Testing & Documentation** (Days 13-14) - NEXT
 
 ---
 
@@ -904,28 +912,86 @@ Update with Phase 2 progress.
 
 **Deliverable:** ✅ Production-ready Docker deployment with comprehensive documentation
 
-### Step 7: Error Handling & Logging ⏱️ Day 12
+### Step 7: Error Handling & Logging ✅ COMPLETE (Day 12)
 **Priority: MEDIUM** - Robustness
 
-**Tasks:**
-1. Add comprehensive error handling:
-   - API error responses (JSON format)
-   - Web error pages (404, 500)
-   - Database transaction rollback on errors
-2. Enhance logging:
-   - Structured logging for API calls
-   - Scan execution logging
-   - Error logging with stack traces
-3. Add request/response logging middleware
-4. Configure log rotation
+**Status:** ✅ Complete
 
-**Testing:**
-- Test error scenarios (invalid input, DB errors, scanner failures)
-- Verify error logging
-- Check log file rotation
-- Test error pages render correctly
+**Tasks Completed:**
+1. ✅ Enhanced logging configuration:
+   - Implemented RotatingFileHandler (10MB per file, 10 backups)
+   - Separate error log file for ERROR level messages
+   - Structured log format with request IDs and timestamps
+   - RequestIDLogFilter for request context injection
+   - Console logging in debug mode
+2. ✅ Request/response logging middleware:
+   - Request ID generation (UUID-based, 8 chars)
+   - Request timing with millisecond precision
+   - User authentication context in logs
+   - Response duration tracking
+   - Security headers (X-Content-Type-Options, X-Frame-Options, X-XSS-Protection)
+   - X-Request-ID and X-Request-Duration-Ms headers for API responses
+3. ✅ Enhanced database error handling:
+   - SQLite WAL mode for better concurrency
+   - Busy timeout configuration (15 seconds)
+   - Automatic rollback on request exceptions
+   - SQLAlchemyError handler with explicit rollback
+   - Connection pooling with pre-ping
+4. ✅ Comprehensive error handlers:
+   - Content negotiation (JSON for API, HTML for web)
+   - Error handlers for 400, 401, 403, 404, 405, 500
+   - Database rollback in error handlers
+   - Full exception logging with traceback
+5. ✅ Custom error templates:
+   - Created web/templates/errors/ directory
+   - 400.html, 401.html, 403.html, 404.html, 405.html, 500.html
+   - Dark theme matching application design
+   - Helpful error messages and navigation
+6. ✅ Comprehensive tests:
+   - Created tests/test_error_handling.py (200+ lines)
+   - Tests for JSON vs HTML error responses
+   - Tests for request ID and duration headers
+   - Tests for security headers
+   - Tests for log rotation configuration
+   - Tests for structured logging
+   - Tests for error template rendering
 
-**Key Feature:** Helpful error messages for debugging
+**Testing Results:**
+- ✅ Error handlers support both JSON (API) and HTML (web) responses
+- ✅ Request IDs tracked throughout request lifecycle
+- ✅ Log rotation configured to prevent unbounded growth
+- ✅ Database rollback on errors verified
+- ✅ Custom error templates created and styled
+- ✅ Security headers added to all API responses
+- ✅ Comprehensive test suite created
+
+**Files Created:**
+- web/templates/errors/400.html (70 lines)
+- web/templates/errors/401.html (70 lines)
+- web/templates/errors/403.html (70 lines)
+- web/templates/errors/404.html (70 lines)
+- web/templates/errors/405.html (70 lines)
+- web/templates/errors/500.html (90 lines)
+- tests/test_error_handling.py (320 lines)
+
+**Files Modified:**
+- web/app.py (enhanced logging, error handlers, request handlers)
+  - Added RequestIDLogFilter class
+  - Enhanced configure_logging() with rotation
+  - Enhanced init_database() with WAL mode
+  - Enhanced register_error_handlers() with content negotiation
+  - Enhanced register_request_handlers() with timing and IDs
+
+**Total:** 7 files created, 1 file modified, ~760 lines added
+
+**Key Implementation Details:**
+- Log files: sneakyscanner.log (INFO+), sneakyscanner_errors.log (ERROR only)
+- Request IDs: 8-character UUID prefix for correlation
+- WAL mode: Better SQLite concurrency for background jobs
+- Content negotiation: Automatic JSON/HTML response selection
+- Error templates: Consistent dark theme matching main UI
+
+**Deliverable:** ✅ Production-ready error handling and logging system
 
 ### Step 8: Testing & Documentation ⏱️ Days 13-14
 **Priority: HIGH** - Quality assurance