Logging in Windows IoT

Effective logging is crucial for monitoring, debugging, and understanding the behavior of your Windows IoT applications. This section covers various aspects of logging on Windows IoT devices, from basic event logging to advanced diagnostic techniques.

Why Logging is Important for IoT

• Device Health Monitoring: Track application status, resource usage, and potential failures.
• Troubleshooting: Diagnose issues remotely by examining logs.
• Performance Analysis: Identify performance bottlenecks and optimize application behavior.
• Auditing: Record security-relevant events and user actions.

Windows Event Logging

Windows IoT leverages the robust Windows Event Log system. Applications can write events to various logs, such as the Application log, System log, or custom logs.

Using Event Viewer

You can access and view event logs on your IoT device using the Event Viewer application. For remote access, you can use the Event Viewer on a Windows desktop machine and connect to your IoT device.

Programmatic Logging with Event Tracing for Windows (ETW)

Event Tracing for Windows (ETW) provides a high-performance, low-overhead tracing facility. It's the recommended method for robust logging in Windows IoT.

Basic ETW Logging Example (C#)

using System.Diagnostics.Tracing;

[EventSource(Name = "MyCompany-MyIoTApp")]
public sealed class MyIoTAppEventSource : EventSource
{
    public static MyIoTAppEventSource Log = new MyIoTAppEventSource();

    private MyIoTAppEventSource() { }

    [Event(1, Message = "Application started with device ID: {0}", Level = EventLevel.Informational)]
    public void AppStart(string deviceId)
    {
        WriteEvent(1, deviceId);
    }

    [Event(2, Message = "Processing sensor data: {0}", Level = EventLevel.Verbose)]
    public void ProcessingSensorData(string data)
    {
        WriteEvent(2, data);
    }

    [Event(3, Message = "Error occurred: {0}", Level = EventLevel.Error)]
    public void AppError(string errorMessage)
    {
        WriteEvent(3, errorMessage);
    }
}

// In your application:
// MyIoTAppEventSource.Log.AppStart("Device-XYZ-123");
// MyIoTAppEventSource.Log.ProcessingSensorData("Temperature: 25C");
// MyIoTAppEventSource.Log.AppError("Failed to connect to network.");
        

Collecting Logs from Devices

For deployed devices, you'll need mechanisms to collect logs. Options include:

• Remote Access: Using SSH or Remote Desktop to access logs directly.
• Cloud Upload: Sending logs to a cloud service like Azure Blob Storage or Azure IoT Hub.
• Log Aggregation Tools: Utilizing agents that collect and forward logs to a central server.

Custom Log Files

While Event Tracing is preferred, some applications might still generate custom log files (e.g., text files). Ensure these are managed efficiently on the device to avoid filling up storage.

Best Practices for Custom Log Files:

• Implement log rotation to manage file sizes.
• Use a consistent, parsable format (e.g., JSON, CSV).
• Consider timestamping all log entries.

Troubleshooting Common Logging Issues

• Logs not appearing: Check ETW provider registration, permissions, and ensure your application is actually writing events.
• High logging overhead: Use verbose logging sparingly, especially in performance-critical sections.
• Storage full: Implement log rotation and archival policies.

Further Reading

For deeper insights into Windows logging mechanisms, refer to the official Microsoft documentation on:

• Event Tracing in Windows
• EventSource (Microsoft Docs)