StarPunk/docs/design/v1.5.0/2025-12-16-phase2-architect-review.md

Phase 2 Architect Review: Debug File Management

Date: 2025-12-17 Reviewer: Architect Agent Phase: 2 - Debug File Management Status: APPROVED

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Executive Summary

Phase 2 implementation meets all acceptance criteria and demonstrates sound architectural decisions. The implementation follows the principle of secure defaults, properly sanitizes user-controlled input, and provides appropriate cleanup mechanisms to prevent resource exhaustion.

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Acceptance Criteria Verification

Criterion	Status	Notes
Debug files disabled by default	PASS	DEBUG_SAVE_FAILED_UPLOADS defaults to False
Files older than 7 days auto-deleted	PASS	Configurable via DEBUG_FILE_MAX_AGE_DAYS
Folder size limited to 100MB	PASS	Configurable via DEBUG_FILE_MAX_SIZE_MB
Filenames sanitized (no path traversal)	PASS	Pattern: alphanumeric, ., _, - only, truncated to 50 chars
Cleanup runs on startup	PASS	Called in create_app() before database init
Tests cover all scenarios	PASS	15 tests covering config, saving, sanitization, cleanup, startup

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Code Review

1. Configuration (starpunk/config.py)

Lines 100-103:

app.config["DEBUG_SAVE_FAILED_UPLOADS"] = os.getenv("DEBUG_SAVE_FAILED_UPLOADS", "false").lower() == "true"
app.config["DEBUG_FILE_MAX_AGE_DAYS"] = int(os.getenv("DEBUG_FILE_MAX_AGE_DAYS", "7"))
app.config["DEBUG_FILE_MAX_SIZE_MB"] = int(os.getenv("DEBUG_FILE_MAX_SIZE_MB", "100"))

Assessment: Correct implementation.

• Boolean parsing uses explicit comparison to "true" (secure)
• Integer parsing uses sensible defaults
• Configuration follows existing patterns in the file

2. Filename Sanitization (starpunk/media.py)

Lines 141-143:

# Sanitize filename to prevent path traversal (v1.5.0 security fix)
safe_filename = "".join(c for c in filename if c.isalnum() or c in "._-")[:50]
debug_file = debug_dir / f"failed_{datetime.now().strftime('%Y%m%d_%H%M%S')}_{safe_filename}"

Assessment: Correct implementation of specified pattern.

• Allowlist approach (only alphanumeric, ., _, -)
• Truncation to 50 characters prevents filesystem issues
• Path traversal attack vectors (../, ..\\, etc.) are neutralized

Security Note: The pattern "._-" correctly allows:

• . for file extensions
• _ for separators
• - for common filename characters

The pattern removes:

• / and \ (path separators)
• : (Windows drive letters)
• <>"|?* (shell metacharacters)
• Null bytes and other control characters

3. Cleanup Function (starpunk/media.py)

Lines 785-857:

Assessment: Well-designed two-phase cleanup algorithm.

Phase 1 - Age-based cleanup:

• Correctly calculates cutoff date
• Uses timedelta for date arithmetic
• Removes from list while iterating (uses slice copy correctly)

Phase 2 - Size-based cleanup:

• Correctly sums remaining file sizes
• Deletes oldest first (proper FIFO approach)
• Loop terminates when under limit or no files remain

Edge cases handled:

• Non-existent directory (early return)
• Empty directory (early return after glob)
• OSError during deletion (logged, continues)

4. Startup Integration (starpunk/__init__.py)

Lines 130-132:

# Clean up old debug files (v1.5.0 Phase 2)
from starpunk.media import cleanup_old_debug_files
cleanup_old_debug_files(app)

Assessment: Correct placement.

• After logging configuration (can log cleanup actions)
• Before database initialization (no DB dependency)
• Uses app instance directly (not current_app, which wouldn't exist yet)

5. Test Coverage

15 tests in 5 test classes:

Class	Tests	Purpose
TestDebugFileConfiguration	4	Verify config defaults and override
TestDebugFileSaving	2	Verify conditional saving behavior
TestDebugFilenameSanitization	3	Security: path traversal, special chars, truncation
TestDebugFileCleanup	5	Age/size limits, edge cases
TestDebugFileStartupCleanup	1	Integration: cleanup during app init

Assessment: Comprehensive coverage of all requirements.

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Security Analysis

Path Traversal Prevention

The sanitization pattern effectively prevents all known path traversal attacks:

Attack Vector	Input	Sanitized Output
Basic traversal	../../../etc/passwd	...etcpasswd
Windows traversal	..\\..\\..\system32	...system32
Encoded traversal	%2e%2e%2f	2e2e2f (%-encoded already decoded before reaching code)
Null byte	file\x00.jpg	file.jpg

Default-Secure Configuration

The feature is disabled by default (DEBUG_SAVE_FAILED_UPLOADS=false), meaning:

• Production deployments are protected without configuration
• Debug files only appear when explicitly enabled
• No accidental data retention in production

Resource Exhaustion Prevention

Dual limits prevent disk exhaustion:

• Age limit (7 days default): Prevents indefinite accumulation
• Size limit (100MB default): Hard cap on disk usage
• Both limits configurable for different environments

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Performance Considerations

Startup Overhead

The cleanup_old_debug_files() function runs on every app startup:

# Worst case: 1000 files in debug directory
# - glob: O(n) directory listing
# - sort: O(n log n)
# - deletion: O(n) unlink calls

# Estimated overhead: ~100ms for 100 files, ~500ms for 1000 files

Assessment: Acceptable. Startup is not a hot path, and the cleanup prevents greater issues.

Recommendation: Consider adding early exit if DEBUG_SAVE_FAILED_UPLOADS=False to skip cleanup entirely in production. However, this is a minor optimization and not required for approval.

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Architectural Alignment

Project Philosophy

"Every line of code must justify its existence."

This implementation follows the philosophy:

• Minimal code (single sanitization pattern)
• Single responsibility (cleanup function does one thing)
• Secure defaults (disabled in production)
• No unnecessary features

Standards Compliance

The implementation follows established patterns:

• Configuration uses existing os.getenv() pattern
• Logging uses app.logger
• File operations use pathlib.Path
• Tests use pytest fixtures

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Minor Observations (Not Blocking)

1. Config validation: The new config options are not validated in validate_config(). Since they have sensible defaults and are non-critical, this is acceptable. However, negative values for MAX_AGE_DAYS or MAX_SIZE_MB could cause unexpected behavior.

2. Logging verbosity: When cleanup deletes many files, it logs a single summary message. This is appropriate for production but could mask issues during debugging.

3. Race condition: If multiple workers start simultaneously, they could attempt to delete the same file. The OSError handling covers this gracefully.

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Verdict

APPROVED

Phase 2 is complete and meets all acceptance criteria. The implementation demonstrates:

• Secure defaults
• Proper input sanitization
• Comprehensive test coverage
• Good error handling
• Alignment with project architecture

The developer may proceed to Phase 3: N+1 Query Fix (Feed Generation).

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Checklist for Project Plan Update

The following items from RELEASE.md Phase 2 are complete:

• Configuration options added (DEBUG_SAVE_FAILED_UPLOADS, DEBUG_FILE_MAX_AGE_DAYS, DEBUG_FILE_MAX_SIZE_MB)
• Cleanup logic implemented in starpunk/media.py
• Config check before saving debug files
• cleanup_old_debug_files() function implemented
• Startup cleanup integrated in __init__.py
• Filename sanitization pattern implemented
• Tests cover all scenarios (15 tests)

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Appendix: Test Verification

$ uv run pytest tests/test_debug_file_management.py -v
================================ 15 passed in 0.72s ============================

$ uv run pytest tests/test_media*.py -v
================================ 33 passed in 6.16s ============================

All tests pass consistently.