hmac-file-server/NETWORK_SWITCHING_IMPROVEMENTS.md

Network Switching Improvements for HMAC File Server

✅ Implementation Complete

The network resilience features have been successfully implemented and are ready to use!

🚀 Quick Start

1. Build the enhanced server:

   ./buildgo.sh
   

2. Use the network-resilient configuration:

   cp config-network-resilience.toml config.toml
   # Edit config.toml with your settings
   

3. Start the server:

   ./hmac-file-server --config config.toml
   

4. Test the features:

   ./test_network_resilience.sh
   

🔧 What's Been Fixed

✅ Implementation Status

✅ Implementation Status

Feature	Status	Description
Chunked/Resumable Uploads	✅ IMPLEMENTED	5MB chunks, survives network interruptions
Network Change Detection	✅ IMPLEMENTED	Monitors interfaces, pauses/resumes uploads
Session Persistence	✅ IMPLEMENTED	Redis or disk storage, 24h default timeout
Enhanced Timeouts	✅ IMPLEMENTED	5-minute read/write, 10-minute idle
Retry Logic	✅ IMPLEMENTED	Exponential backoff with jitter
Backward Compatibility	✅ GUARANTEED	Zero changes to existing upload handlers

📂 New Files Added

• cmd/server/upload_session.go - Session management and persistence
• cmd/server/network_resilience.go - Network monitoring and pause/resume
• cmd/server/chunked_upload_handler.go - New chunked upload endpoint
• cmd/server/integration.go - Non-intrusive integration layer
• config-network-resilience.toml - Ready-to-use configuration
• test_network_resilience.sh - Automated testing script

🌐 New API Endpoints

Endpoint	Method	Purpose
/chunked-upload	POST	Start new chunked upload session
/chunked-upload	PUT	Upload individual chunks
/upload-status	GET	Check upload progress
/upload	POST	Traditional uploads (unchanged)

📱 Network Switching Benefits

Before (Problems Fixed)

• ❌ Upload fails completely on network interruption
• ❌ Progress lost when switching WiFi/WLAN
• ❌ Large files problematic on mobile networks
• ❌ No recovery from connection drops

After (Solutions Implemented)

• ✅ Seamless network switching - uploads pause and resume automatically
• ✅ Progress preservation - no lost data during interruptions
• ✅ Mobile optimized - 5MB chunks perfect for cellular/WiFi
• ✅ Intelligent retry - exponential backoff handles temporary failures
• ✅ Session persistence - survives server restarts

📋 Usage Examples

Traditional Upload (Unchanged)

curl -X POST -H "X-Signature: HMAC" -F 'file=@document.pdf' http://localhost:8080/upload

New Chunked Upload

# 1. Start session
curl -X POST \
  -H "X-Filename: large_video.mp4" \
  -H "X-Total-Size: 104857600" \
  -H "X-Signature: HMAC" \
  http://localhost:8080/chunked-upload

# 2. Upload chunks (automatically handles network switches)
curl -X PUT \
  -H "X-Upload-Session-ID: session_123" \
  -H "X-Chunk-Number: 0" \
  --data-binary @chunk_0.bin \
  http://localhost:8080/chunked-upload

# 3. Check progress
curl "http://localhost:8080/upload-status?session_id=session_123"

⚙️ Configuration

Essential settings for network resilience:

[server]
networkevents = true              # Enable network monitoring

[uploads]  
chunkeduploadsenabled = true      # Enable chunked uploads
chunksize = "5MB"                 # Optimal for mobile
sessiontimeout = "24h"            # Session persistence

[timeouts]
readtimeout = "300s"              # 5 minutes for mobile
writetimeout = "300s"             # 5 minutes for slow networks
idletimeout = "600s"              # 10 minutes keep-alive

🔨 Build & Deploy

Build Process

# Automatic build with network resilience detection
./buildgo.sh

# Output confirms features are included:
# [INFO] Found network resilience: upload_session.go
# [INFO] Found network resilience: network_resilience.go  
# [INFO] Found network resilience: chunked_upload_handler.go
# [INFO] Found network resilience: integration.go
# [BUILD] Build successful! Binary created: ./hmac-file-server

Testing

# Comprehensive feature testing
./test_network_resilience.sh

# Expected output:
# ✅ Traditional upload works
# ✅ Chunked upload session creation works  
# ✅ Upload status endpoint works
# ✅ Health endpoint works
# ✅ Metrics endpoint works

🎯 Perfect for Your Use Case

This implementation specifically solves your notebook network switching problem:

1. WLAN ↔ WiFi Switching: Uploads automatically pause during network changes and resume when stable
2. Mobile-Friendly: 5MB chunks work well over cellular and WiFi connections
3. Android/iOS Compatible: HTTP-based solution works with any mobile platform
4. Zero Disruption: Existing users see no changes, new users get enhanced reliability
5. Production Ready: Full session persistence, monitoring, and error handling

Your users can now upload large files from notebooks/mobile devices without worrying about network switching interrupting their transfers! 🚀