hmac-file-server/STABILITY_AUDIT_PLAN.md

HMAC File Server 3.2 - Stability & Reliability Audit Plan

🎯 Objective

Comprehensive code audit focused on STABILITY and RELIABILITY without rewriting core functions. Identify potential issues that could cause crashes, data loss, memory leaks, race conditions, or degraded performance.

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📋 Audit Categories

1. CONCURRENCY & THREAD SAFETY 🔄

Priority: CRITICAL

Areas to Check:

• Mutex Usage Patterns
  • confMutex (main.go:332) - Global config protection
  • spilloverMutex (queue_resilience.go:18) - Queue operations
  • healthMutex (queue_resilience.go:40) - Health monitoring
  • logMu (main.go:378) - Logging synchronization

Specific Checks:

• Lock Ordering - Prevent deadlocks between multiple mutexes
• Lock Duration - Ensure locks aren't held too long
• Read vs Write Locks - Verify appropriate RWMutex usage
• Defer Patterns - Check all defer mutex.Unlock() calls
• Channel Operations - Network event channels, upload queues
• Goroutine Lifecycle - Worker pools, monitoring routines

Files to Audit:

• main.go (lines around 300, 332, 378, 822)
• queue_resilience.go (mutex operations throughout)
• network_resilience.go (concurrent monitoring)
• upload_session.go (session management)

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2. ERROR HANDLING & RECOVERY ⚠️

Priority: HIGH

Areas to Check:

• Fatal Error Conditions - Review all log.Fatal* calls
• Panic Recovery - Missing recover() handlers
• Error Propagation - Proper error bubbling up
• Resource Cleanup - Ensure cleanup on errors
• Graceful Degradation - Fallback mechanisms

Critical Fatal Points:

• main.go:572 - Config creation failure
• main.go:577 - Configuration load failure
• main.go:585 - Validation failure
• main.go:625 - Configuration errors
• main.go:680 - PID file errors
• helpers.go:97 - MinFreeBytes parsing
• helpers.go:117 - TTL configuration

Error Patterns to Check:

• Database connection failures
• File system errors (disk full, permissions)
• Network timeouts and failures
• Memory allocation failures
• Configuration reload errors

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3. RESOURCE MANAGEMENT 💾

Priority: HIGH

Areas to Check:

• File Handle Management

  • Verify all defer file.Close() calls
  • Check for file handle leaks
  • Monitor temp file cleanup

• Memory Management

  • Buffer pool usage (bufferPool in main.go:363)
  • Large file upload handling
  • Memory leak patterns in long-running operations

• Network Connections

  • HTTP connection pooling
  • Client session tracking
  • Connection timeout handling

• Goroutine Management

  • Worker pool lifecycle
  • Background task cleanup
  • WaitGroup usage patterns

Files to Focus:

• main.go (buffer pools, file operations)
• helpers.go (file operations, defer patterns)
• upload_session.go (session cleanup)
• adaptive_io.go (large file handling)

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4. CONFIGURATION & INITIALIZATION ⚙️

Priority: MEDIUM

Areas to Check:

• Default Values - Ensure safe defaults
• Validation Logic - Prevent invalid configurations
• Runtime Reconfiguration - Hot reload safety
• Missing Required Fields - Graceful handling
• Type Safety - String to numeric conversions

Configuration Files:

• config_simplified.go - Default generation
• config_validator.go - Validation rules
• config_test_scenarios.go - Edge cases

Validation Points:

• Network timeouts and limits
• File size restrictions
• Path validation and sanitization
• Security parameter validation

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5. NETWORK RESILIENCE STABILITY 🌐

Priority: HIGH (Recently added features)

Areas to Check:

• Network Monitoring Loops - Prevent infinite loops
• Interface Detection - Handle missing interfaces gracefully
• Quality Metrics - Prevent division by zero
• State Transitions - Ensure atomic state changes
• Timer Management - Prevent timer leaks

Files to Audit:

• network_resilience.go - Core network monitoring
• client_network_handler.go - Client session tracking
• integration.go - System integration points

Specific Concerns:

• Network interface enumeration failures
• RTT measurement edge cases
• Quality threshold calculations
• Predictive switching logic

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6. UPLOAD PROCESSING STABILITY 📤

Priority: HIGH

Areas to Check:

• Chunked Upload Sessions - Session state consistency
• File Assembly - Partial upload handling
• Temporary File Management - Cleanup on failures
• Concurrent Uploads - Rate limiting effectiveness
• Storage Quota Enforcement - Disk space checks

Files to Audit:

• chunked_upload_handler.go - Session management
• upload_session.go - State tracking
• main.go - Core upload logic
• helpers.go - File operations

Edge Cases:

• Disk full during upload
• Network interruption mid-upload
• Client disconnect scenarios
• Large file timeout handling

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7. LOGGING & MONITORING RELIABILITY 📊

Priority: MEDIUM

Areas to Check:

• Log File Rotation - Prevent disk space issues
• Metrics Collection - Avoid blocking operations
• Debug Logging - Performance impact in production
• Log Level Changes - Runtime safety
• Structured Logging - Consistency and safety

Files to Audit:

• helpers.go (logging setup)
• main.go (debug statements)
• Metrics initialization and collection

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8. EXTERNAL DEPENDENCIES 🔗

Priority: MEDIUM

Areas to Check:

• Database Connections - Connection pooling and timeouts
• Redis Integration - Failure handling
• File System Operations - Permission and space checks
• System Calls - Error handling
• Third-party Libraries - Version compatibility

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🔍 Audit Methodology

Phase 1: Static Code Analysis (2-3 hours)

1. Concurrency Pattern Review - Mutex usage, race conditions
2. Error Handling Audit - Fatal conditions, recovery patterns
3. Resource Leak Detection - File handles, memory, goroutines
4. Configuration Safety - Validation and defaults

Phase 2: Dynamic Analysis Preparation (1-2 hours)

1. Test Scenario Design - Edge cases and failure modes
2. Monitoring Setup - Memory, CPU, file handles
3. Load Testing Preparation - Concurrent upload scenarios
4. Network Failure Simulation - Interface switching tests

Phase 3: Code Pattern Verification (2-3 hours)

1. TODO/FIXME Review - Incomplete implementations
2. Debug Code Cleanup - Production-ready logging
3. Performance Bottleneck Analysis - Blocking operations
4. Security Pattern Review - Input validation, path traversal

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🚨 High-Risk Areas Identified

1. Multiple Fatal Conditions (main.go)

• Configuration failures cause immediate exit
• No graceful degradation for non-critical failures

2. Complex Mutex Hierarchies (queue_resilience.go)

• Multiple mutexes could create deadlock scenarios
• Lock duration analysis needed

3. Network Monitoring Loops (network_resilience.go)

• Background goroutines with complex state management
• Timer and resource cleanup verification needed

4. File Handle Management (throughout)

• Multiple file operations without centralized tracking
• Temp file cleanup verification needed

5. Buffer Pool Usage (main.go)

• Memory management in high-concurrency scenarios
• Pool exhaustion handling

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📈 Success Criteria

✅ Stability Improvements

• No race conditions detected
• Proper resource cleanup verified
• Graceful error handling confirmed
• Memory leak prevention validated

✅ Reliability Enhancements

• Fault tolerance for external dependencies
• Robust configuration validation
• Comprehensive error recovery
• Production-ready logging

✅ Performance Assurance

• No blocking operations in critical paths
• Efficient resource utilization
• Proper cleanup and garbage collection
• Scalable concurrency patterns

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🔧 Tools and Techniques

1. Static Analysis

   • go vet - Built-in Go analyzer
   • golangci-lint - Comprehensive linting
   • Manual code review with focus areas

2. Race Detection

   • go build -race - Runtime race detector
   • Concurrent test scenarios

3. Memory Analysis

   • go tool pprof - Memory profiling
   • Long-running stability tests

4. Resource Monitoring

   • File handle tracking
   • Goroutine leak detection
   • Network connection monitoring

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📝 Deliverables

1. Stability Audit Report - Detailed findings and recommendations
2. Code Improvement Patches - Non-invasive fixes for identified issues
3. Test Suite Enhancements - Edge case and failure mode tests
4. Production Monitoring Guide - Key metrics and alerts
5. Deployment Safety Checklist - Pre-deployment verification steps

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This audit plan prioritizes stability and reliability while respecting the core architecture and avoiding rewrites of essential functions.