Denso/docs/development/RealtimeIntegration.md

Realtime Integration Guide / Hướng dẫn Tích hợp Realtime

📋 Overview / Tổng quan

Tài liệu này mô tả cách tích hợp tính năng Linux realtime (preempt_rt) vào ScriptTask và cách enable/disable tính năng này ở compile time.

🔧 Enabling Realtime Support / Bật Hỗ trợ Realtime

Step 1: Uncomment DefineConstants / Bỏ comment DefineConstants

Trong file RobotNet10.ScriptEngine.csproj, uncomment dòng sau:

<PropertyGroup>
  <TargetFramework>net10.0</TargetFramework>
  <ImplicitUsings>enable</ImplicitUsings>
  <Nullable>enable</Nullable>
  <!-- Define REALTIME symbol to enable Linux realtime features -->
  <DefineConstants>$(DefineConstants);REALTIME</DefineConstants>
</PropertyGroup>

Step 2: Build Project / Build Dự án

dotnet build srcs/RobotNet10/Commons/RobotNet10.ScriptEngine/RobotNet10.ScriptEngine.csproj

Khi REALTIME symbol được define:

• Code realtime sẽ được compile vào binary
• ScriptTask sẽ sử dụng RealtimeTimer thay vì System.Threading.Timer
• Có thể configure realtime scheduling policy và CPU affinity

Khi REALTIME symbol KHÔNG được define:

• Code realtime sẽ bị loại bỏ hoàn toàn (không compile)
• ScriptTask sử dụng System.Threading.Timer (standard .NET timer)
• Không có dependency vào Linux-specific APIs

📝 Usage Examples / Ví dụ Sử dụng

Example 1: Basic Realtime Task / Task Realtime Cơ bản

using RobotNet10.ScriptEngine.Models;
using Microsoft.CodeAnalysis.Scripting;

// Create ScriptTaskModel with compiled script runner
var taskModel = new ScriptTaskModel(
    name: "HighPriorityTask",
    interval: 1, // 1 second
    autoStart: true,
    code: scriptCode,
    runner: compiledScriptRunner
);

// Create ScriptGlobals with dictionaries
var globals = new ScriptGlobals(
    scriptRobotNet: robotNetGlobals,
    scriptApp: appGlobals,
    scriptVariables: variables,
    scriptParameters: parameters
);

// Create task with realtime options
var realtimeOptions = new RealtimeTaskOptions
{
    Enabled = true,
    SetSchedulingPolicy = true,
    SchedulingPolicy = RealtimeSchedulingPolicy.Fifo,
    Priority = 50,
    ClockType = RealtimeClockType.Monotonic
};

var task = new ScriptTask(
    model: taskModel,
    globals: globals,
    realtimeOptions: realtimeOptions
);

Example 2: Task with CPU Affinity / Task với CPU Affinity

var taskModel = new ScriptTaskModel(
    name: "PinnedTask",
    interval: 2,
    autoStart: true,
    code: scriptCode,
    runner: compiledScriptRunner
);

var globals = new ScriptGlobals(
    scriptRobotNet: robotNetGlobals,
    scriptApp: appGlobals,
    scriptVariables: variables,
    scriptParameters: parameters
);

var realtimeOptions = new RealtimeTaskOptions
{
    Enabled = true,
    SetSchedulingPolicy = true,
    SchedulingPolicy = RealtimeSchedulingPolicy.Fifo,
    Priority = 75,
    CpuAffinity = new[] { 0, 1 }, // Pin to CPU 0 and 1
    ClockType = RealtimeClockType.Monotonic
};

var task = new ScriptTask(
    model: taskModel,
    globals: globals,
    realtimeOptions: realtimeOptions
);

Example 3: Disable Realtime for Specific Task / Tắt Realtime cho Task Cụ thể

var taskModel = new ScriptTaskModel(
    name: "StandardTask",
    interval: 5,
    autoStart: true,
    code: scriptCode,
    runner: compiledScriptRunner
);

var globals = new ScriptGlobals(
    scriptRobotNet: robotNetGlobals,
    scriptApp: appGlobals,
    scriptVariables: variables,
    scriptParameters: parameters
);

var realtimeOptions = new RealtimeTaskOptions
{
    Enabled = false // Use standard timer even if REALTIME is defined
};

var task = new ScriptTask(
    model: taskModel,
    globals: globals,
    realtimeOptions: realtimeOptions
);

Example 4: Without Realtime Options / Không có Realtime Options

var taskModel = new ScriptTaskModel(
    name: "StandardTask",
    interval: 10,
    autoStart: true,
    code: scriptCode,
    runner: compiledScriptRunner
);

var globals = new ScriptGlobals(
    scriptRobotNet: robotNetGlobals,
    scriptApp: appGlobals,
    scriptVariables: variables,
    scriptParameters: parameters
);

// If realtimeOptions is null or not provided, uses standard timer
var task = new ScriptTask(
    model: taskModel,
    globals: globals
    // realtimeOptions: null (default)
);

⚙️ RealtimeTaskOptions Configuration / Cấu hình RealtimeTaskOptions

Property	Type	Default	Description
Enabled	bool	true	Enable/disable realtime features for this task
SetSchedulingPolicy	bool	true	Whether to set realtime scheduling policy
SchedulingPolicy	RealtimeSchedulingPolicy	Fifo	SCHED_FIFO or SCHED_RR
Priority	int	50	Priority (1-99, higher = higher priority)
CpuAffinity	int[]?	null	CPU cores to pin thread to (null = no affinity)
ClockType	RealtimeClockType	Monotonic	Clock type for timer (Monotonic recommended)
NonBlocking	bool	false	Note: Always set to true internally for async monitoring

🎯 How It Works / Cách Hoạt động

Without REALTIME Symbol / Không có REALTIME Symbol

graph LR
    A[ScriptTask.Start] --> B[System.Threading.Timer]
    B --> C[ExecuteTask callback]
    C --> D[Task execution]

With REALTIME Symbol / Có REALTIME Symbol

graph LR
    A[ScriptTask.Start] --> B{RealtimeOptions<br/>Enabled?}
    B -->|Yes| C[RealtimeTimer<br/>timerfd]
    B -->|No| D[System.Threading.Timer]
    C --> E[Create Dedicated Thread<br/>Highest Priority]
    E --> F[Set Scheduling Policy<br/>SCHED_FIFO/RR in thread]
    E --> G[Set CPU Affinity<br/>in thread if configured]
    E --> H[MonitorRealtimeTimer<br/>loop in thread]
    H --> I[ReadExpirations<br/>non-blocking]
    I --> J{Is Paused?}
    J -->|No| K[ExecuteTask]
    J -->|Yes| L[Skip Execution]
    D --> K

🔑 Key Features / Tính năng Chính

1. High-Resolution Timer / Timer Độ phân giải Cao

• RealtimeTimer: Sử dụng Linux timerfd API
• Accuracy: Nanosecond precision
• Better than: System.Threading.Timer (millisecond precision)

2. Dedicated Thread with Highest Priority / Thread Riêng với Độ Ưu tiên Cao nhất

• Dedicated Thread: Tạo thread riêng cho realtime monitoring với IsBackground = false
• Thread Priority: Set SCHED_FIFO/SCHED_RR với priority cao nhất trong thread
• Isolation: Realtime monitoring chạy độc lập, không bị ảnh hưởng bởi các thread khác
• CPU Affinity: Pin thread to specific CPU cores (nếu configured)
• Reduces cache misses: Improves determinism

3. Real-time Scheduling / Lập lịch Real-time

• SCHED_FIFO: First-In-First-Out, highest priority threads run first
• SCHED_RR: Round-Robin, time-sliced real-time scheduling
• Priority: 1-99 (higher = higher priority)
• Applied in thread: Scheduling policy được set trong dedicated thread, không ảnh hưởng main thread

4. Pause/Resume Behavior / Hành vi Pause/Resume

• Timer continues: Khi paused, timer/realtime loop vẫn tiếp tục chạy
• Skip execution: Chỉ skip execution khi timer expire (check _isPaused flag)
• Instant resume: Resume ngay lập tức không cần restart timer
• No interruption: Timer không bị gián đoạn khi pause/resume

5. ScriptTask Constructor / Constructor của ScriptTask

• ScriptTaskModel: Nhận model chứa metadata và ScriptRunner<object>
• ScriptGlobals: Nhận globals dictionary với ScriptRobotNet, ScriptApp, ScriptVariables, ScriptParameters
• Logger: Tự động lấy từ globals.ScriptRobotNet.TryGetValue("get_Logger", ...)
• Execution: Gọi model.Runner(globals) trực tiếp, không merge dictionaries

6. Fallback Mechanism / Cơ chế Dự phòng

• Nếu realtime initialization fails, falls back to standard timer
• Logs error but continues operation
• Ensures system reliability

⚠️ Important Notes / Lưu Ý Quan trọng

1. Root Privileges / Quyền Root

Realtime scheduling requires root privileges or capabilities:

# Option 1: Run with sudo
sudo dotnet run

# Option 2: Set capabilities (recommended for production)
sudo setcap cap_sys_nice+ep /path/to/your/app

2. Platform Specific / Phụ thuộc Nền tảng

• Only works on Linux: Realtime features require Linux kernel
• preempt_rt recommended: For best real-time performance
• Windows/macOS: Code compiles but realtime features are disabled

3. Performance Considerations / Xem xét Hiệu năng

• RealtimeTimer: More accurate but requires Linux
• Standard Timer: Cross-platform but less accurate
• Choose based on: Target platform and accuracy requirements

4. Error Handling / Xử lý Lỗi

• Realtime initialization errors are caught and logged
• System automatically falls back to standard timer
• Task continues to function normally

📊 Comparison / So sánh

Feature	Standard Timer	Realtime Timer
Platform	Cross-platform	Linux only
Accuracy	~1ms	Nanosecond
Scheduling	OS default	SCHED_FIFO/RR
CPU Affinity	No	Yes
Root Required	No	Yes (for scheduling)
Compile-time	Always available	Requires REALTIME symbol

🔗 Related Documents / Tài liệu Liên quan

• RobotNet10.Realtime README - Realtime library documentation
• Appccelerate.StateMachine Guide - State machine usage
• ScriptTask Implementation - Reference implementation

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Last Updated: 2025-11-13 Status: Integration Guide Version: 1.0