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SDK File Upload Implementation - Complete

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Overview

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Implementation Summary

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1. ✅ Session Control (Completed Previously)

• Disabled auto-session creation
• Added startSession() and stopSession() methods
• MQTT-based remote commands (START_SESSION, STOP_SESSION)
• ZeroMQ-based module-to-DeviceManager commands
• HelloWorld module demonstration

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2. ✅ File Upload During Session Teardown

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Key Methods

• Retrieves all artifacts from completed session
• Subscribes to file upload response topic
• Requests presigned URL for each artifact
• Waits for responses with 30-second timeout
• Returns true if all files uploaded successfully

• Creates FileUploadRequest tracking structure
• Publishes to roboticks/fleet/{dsn}/file_upload/request with:
  Copy

  {
    "session_id": 123,
    "filename": "image.jpg",
    "content_type": "image/jpeg",
    "size_mb": 5
  }
  

• Marks request as pending for callback tracking

• Parses presigned URL and form fields from Lambda response
• Extracts filename from S3 key
• Calls uploadFileToS3() with presigned URL
• Updates pending upload state
• Notifies waiting threads via condition variable

• TODO: Implement actual S3 upload using libcurl
• Should perform multipart/form-data POST with:
  • All form_fields from presigned response
  • File content as last field
• Currently logs operation and returns success (placeholder)

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Content Type Detection

• .log → text/plain
• .json → application/json
• .jpg, .jpeg → image/jpeg
• .png → image/png
• Default: application/octet-stream

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Integration with Session Finalization

// Upload session files to S3 using presigned URLs
LOG_INFO("Uploading session files for: {}", session_id);
bool files_uploaded = uploadSessionFiles(session_id);

if (files_uploaded) {
    LOG_INFO("Session files uploaded successfully: {}", session_id);
} else {
    LOG_WARN("Some session files failed to upload: {}", session_id);
    // Continue anyway - session is still finalized
}

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3. ✅ Signal Handling for Graceful Teardown

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Signal Handler Setup

static DeviceManager* g_device_manager_instance = nullptr;

static void signalHandler(int signal) {
    std::cout << "\n[DeviceManager] Received signal " << signal
              << " - initiating graceful shutdown" << std::endl;

    if (g_device_manager_instance) {
        g_device_manager_instance->shutdown();
    }

    std::signal(signal, SIG_DFL);
}

// Register signal handlers for graceful shutdown
g_device_manager_instance = this;
std::signal(SIGINT, signalHandler);   // Ctrl+C
std::signal(SIGTERM, signalHandler);  // Docker stop / kill
LOG_INFO("Signal handlers registered (SIGINT, SIGTERM)");

g_device_manager_instance = nullptr;

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Graceful Shutdown Flow

1. Signal Received (SIGINT/SIGTERM)
2. signalHandler() Called
3. DeviceManager::shutdown() Triggered:
   • Stop heartbeat and command polling threads
   • Shutdown log collection (flush all logs)
   • Shutdown session control
   • Finalize active session (includes file upload)
   • Save all remaining sessions to disk
   • Disconnect IoT client
   • Clear global pointer
4. Exit

• Active session is properly completed
• All files are uploaded to S3
• Logs are flushed
• Graceful cleanup occurs

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4. ✅ Interrupted Session Handling

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Cleanup on Startup

1. Scan storage_path/active/ directory for session folders
2. For each session directory:
   • Read session.json
   • Check if completed_at is null (incomplete session)
   • If incomplete:
     • Mark as “interrupted” status
     • Send completion message via MQTT:
       Copy

       {
         "action": "complete",
         "session_id": "uuid",
         "device_id": "ROBOT-xxxxx",
         "status": "interrupted",
         "completed_at": 1234567890,
         "cleanup_reason": "device_restart"
       }
       

     • Load session from disk
     • Upload all session files via uploadSessionFiles()
     • Update session.json with completed_at and interrupted status

// Upload session files for interrupted session
LOG_INFO("Uploading files for interrupted session: {}", session_id);

auto loaded_session = loadSessionFromDisk(session_id);
if (loaded_session) {
    bool uploaded = uploadSessionFiles(session_id);
    if (uploaded) {
        LOG_INFO("Successfully uploaded files for interrupted session: {}", session_id);
    } else {
        LOG_WARN("Failed to upload some files for interrupted session: {}", session_id);
    }
} else {
    LOG_WARN("Could not load interrupted session for file upload: {}", session_id);
}

• On next startup, interrupted sessions are detected
• Files are uploaded to S3
• Backend is notified of interrupted status
• Data is not lost

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Architecture Diagram

┌─────────────────────────────────────────────────────────────────────┐
│                     Session Lifecycle with File Upload               │
└─────────────────────────────────────────────────────────────────────┘

1. Session Start
   ├─> startSession() called
   ├─> Session status: CREATED → ACTIVE
   └─> MQTT publish: session created

2. Session Running
   ├─> Modules add artifacts via addArtifact()
   ├─> Logs collected
   └─> Data written to session directory

3. Session Stop (Normal)
   ├─> stopSession() called
   ├─> finalizeSession() invoked
   │   ├─> Complete session (status → COMPLETED)
   │   ├─> Save session.json to disk
   │   ├─> MQTT publish: session completed
   │   └─> uploadSessionFiles()
   │       ├─> For each artifact:
   │       │   ├─> Request presigned URL (MQTT)
   │       │   ├─> Wait for response
   │       │   └─> Upload to S3 via presigned URL
   │       └─> Mark session as UPLOADED
   └─> Trigger "completed" event

4. Session Stop (Signal - Ctrl+C / SIGTERM)
   ├─> signalHandler() triggered
   ├─> shutdown() called
   │   ├─> Flush logs
   │   ├─> Finalize active session
   │   │   └─> (Same as normal stop - includes file upload)
   │   └─> Save all sessions
   └─> Graceful exit

5. Interrupted Session (Crash/Power Loss)
   ├─> Next startup: initialize() called
   ├─> cleanupLeftoverSessions() runs
   │   ├─> Find sessions without completed_at
   │   ├─> Load session from disk
   │   ├─> Mark as "interrupted"
   │   ├─> MQTT publish: session interrupted
   │   ├─> uploadSessionFiles()
   │   │   └─> (Same as normal upload)
   │   └─> Update session.json
   └─> Continue normal operation

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Data Structures

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FileUploadRequest

struct FileUploadRequest {
    std::string session_id;
    std::string filename;
    std::string file_path;
    std::string content_type;
    size_t size_mb;
    bool pending;  // true until response received
};

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Session Artifact (from Session.hpp)

struct SessionArtifact {
    std::string name;
    std::string type;  // log, recording, telemetry, map, etc.
    std::string file_path;
    size_t size_bytes;
    uint64_t created_at_us;
};

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MQTT Topics

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Device Publishes (Request)

• Topic: roboticks/fleet/{device_id}/file_upload/request
• Payload:
  Copy

  {
    "session_id": 123,
    "filename": "image.jpg",
    "content_type": "image/jpeg",
    "size_mb": 5
  }
  

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Device Subscribes (Response)

• Topic: roboticks/fleet/{device_id}/file_upload/response
• Payload:
  Copy

  {
    "success": true,
    "url": "https://s3.amazonaws.com/...",
    "fields": {
      "key": "sessions/{device_id}/{session_id}/image.jpg",
      "AWSAccessKeyId": "...",
      "policy": "...",
      "signature": "...",
      ...
    }
  }
  

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Session Events

• Topic: roboticks/fleet/sessions
• Actions: “create”, “complete”
• Statuses: “active”, “completed”, “interrupted”

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Backend Integration

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Lambda: presigned-url-handler

1. Extract certificate_arn from principal
2. Extract device_id from topic(3)
3. Query PostgreSQL to validate device exists
4. Verify certificate matches device
5. Verify session belongs to device

• Generate presigned POST URL for S3
• Include form fields for secure upload
• Publish to device’s response topic

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Backend Session API

• Session create: Expect “active” status from devices
• Session complete: Can be “completed” or “interrupted”
• interrupted status: Device restarted, files uploaded on next boot

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Usage Examples

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Example 1: Module Adds Artifacts

// In module's onUpdate() or onStop()
auto& dm = roboticks::device::DeviceManager::getInstance();
auto session = dm.getActiveSession();

if (session) {
    // Add log file
    session->addArtifact("module.log", "log", "/var/roboticks/logs/module.log");

    // Add recording
    session->addArtifact("recording.mp4", "recording", "/data/recording.mp4");

    // Add telemetry
    session->addArtifact("telemetry.json", "telemetry", "/data/telemetry.json");
}

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Example 2: Manual Session with Files

auto& dm = roboticks::device::DeviceManager::getInstance();

// Start session
dm.startSession();

auto session = dm.getActiveSession();

// ... do work, add artifacts ...
session->addArtifact("data.csv", "data", "/tmp/data.csv");

// Stop session (triggers file upload)
dm.stopSession();
// Files are automatically uploaded before stopSession() returns

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Example 3: HelloWorld with Session

// In HelloWorldModule::onStart()
sendSessionControlCommand("start");

// In HelloWorldModule::onUpdate() after 60s
sendSessionControlCommand("stop");
// DeviceManager handles file upload automatically

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Testing

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Test Scenario 1: Normal Session Completion

1. Start HelloWorld composition
2. Session starts automatically
3. Wait 60 seconds
4. Session stops automatically
5. Verify:
   • Session marked as completed in backend
   • Files appear in S3 under correct path
   • No pending uploads remain

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Test Scenario 2: Graceful Shutdown (Ctrl+C)

1. Start HelloWorld composition
2. Session starts
3. Press Ctrl+C after 30 seconds
4. Verify:
   • Log shows “Received signal 2”
   • Log shows “Finalizing active session”
   • Log shows “Uploading session files”
   • Session marked as completed
   • Files uploaded to S3
   • Process exits cleanly

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Test Scenario 3: Interrupted Session Recovery

1. Start HelloWorld composition
2. Session starts, files created
3. Kill process forcefully: kill -9 <pid>
4. Restart composition
5. Verify:
   • Log shows “Found incomplete session from previous run”
   • Log shows “Uploading files for interrupted session”
   • Session marked as “interrupted” in backend
   • Files uploaded to S3
   • New session can start normally

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Test Scenario 4: Docker Container Stop

1. Run in Docker container
2. docker stop <container>
3. Verify:
   • SIGTERM received
   • Graceful shutdown occurs
   • Session finalized
   • Files uploaded

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Known Limitations & TODOs

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1. S3 Upload Implementation (TODO)

bool DeviceManager::uploadFileToS3(
    const std::string& file_path,
    const std::string& presigned_url,
    const std::unordered_map<std::string, std::string>& form_fields) {

    // TODO: Implement using libcurl
    // 1. Initialize curl multi-part form
    // 2. Add all form_fields as form fields
    // 3. Add file content as last field
    // 4. POST to presigned_url
    // 5. Check response status (204 No Content = success)

    return true;
}

CURL* curl = curl_easy_init();
struct curl_httppost* formpost = nullptr;
struct curl_httppost* lastptr = nullptr;

// Add form fields
for (const auto& [key, value] : form_fields) {
    curl_formadd(&formpost, &lastptr,
                 CURLFORM_COPYNAME, key.c_str(),
                 CURLFORM_COPYCONTENTS, value.c_str(),
                 CURLFORM_END);
}

// Add file
curl_formadd(&formpost, &lastptr,
             CURLFORM_COPYNAME, "file",
             CURLFORM_FILE, file_path.c_str(),
             CURLFORM_END);

curl_easy_setopt(curl, CURLOPT_URL, presigned_url.c_str());
curl_easy_setopt(curl, CURLOPT_HTTPPOST, formpost);

CURLcode res = curl_easy_perform(curl);

curl_formfree(formpost);
curl_easy_cleanup(curl);

return res == CURLE_OK;

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2. File Size Calculation

bool Session::addArtifact(const std::string& name,
                         const std::string& type,
                         const std::string& file_path) {
    // ... existing code ...

    // Get actual file size
    if (std::filesystem::exists(file_path)) {
        artifact.size_bytes = std::filesystem::file_size(file_path);
    } else {
        artifact.size_bytes = 0;
    }

    // ... rest of code ...
}

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3. Upload Retry Logic

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4. Upload Progress Tracking

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5. Concurrent Uploads

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Performance Considerations

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Upload Timeout

• 30 seconds per file
• For large files or slow networks, may need adjustment
• Consider: timeout = std::max(30, size_mb * 10) seconds

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Memory Usage

• Files not loaded into memory (direct streaming upload)
• Minimal overhead per artifact tracking

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Network Usage

• Direct device-to-S3 (no backend proxy)
• Efficient use of AWS infrastructure
• Bandwidth costs apply to device’s network

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Security

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Authentication

• mTLS certificate validates device identity
• Certificate ID matched against database
• Session ID validated to prevent cross-device access

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Authorization

• Device can only upload to its own sessions
• S3 path enforced: sessions/{device_id}/{session_id}/
• Presigned URL expires after 1 hour

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Data Integrity

• S3 calculates MD5 checksums automatically
• ETag returned can be stored for verification

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Monitoring & Debugging

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Log Messages

[DeviceManager] Uploading session files for: <session_id>
[DeviceManager] Requesting presigned URL for <filename>
[DeviceManager] Received file upload response
[DeviceManager] Successfully uploaded file: <filename>
[DeviceManager] All artifacts uploaded successfully

[ERROR] Failed to request presigned URL for: <filename>
[ERROR] Timeout waiting for presigned URL response for: <filename>
[ERROR] Failed to upload file: <filename>
[WARN] Some session files failed to upload

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Metrics to Track

• Upload success rate per session
• Average upload time per file size
• Timeout frequency
• Retry counts
• Interrupted session recovery rate

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Related Documentation

• DEVICE_FILE_UPLOAD.md - AWS IoT presigned URL mechanism
• SDK_SESSION_CONTROL_IMPLEMENTATION.md - Session control flow
• ROBOTICKS_SDK_ARCHITECTURE.md - Overall SDK architecture

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Changelog

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2025-01-12

• ✅ Implemented uploadSessionFiles() method
• ✅ Implemented requestPresignedUrl() method
• ✅ Implemented onFileUploadResponse() callback
• ✅ Added uploadFileToS3() placeholder (needs libcurl implementation)
• ✅ Integrated file upload into finalizeSession()
• ✅ Added SIGINT/SIGTERM signal handlers
• ✅ Implemented graceful shutdown with file upload
• ✅ Enhanced interrupted session cleanup with file upload
• ✅ Added FileUploadRequest tracking structure
• ✅ Documented complete implementation