Log Levels

What are Log Levels?

Log levels indicate the severity or importance of a log message. They help filter logs and focus on what matters.

Six Log Levels

Level	Value	Description	When to Use
Trace	0	Most detailed	Detailed debugging, rarely used
Debug	1	Debugging info	Development debugging
Information	2	General info	Normal application flow
Warning	3	Unexpected events	Recoverable issues
Error	4	Errors/exceptions	Operation failures
Critical	5	Critical failures	Application crashes

When to Use Each Level

Trace

Very detailed information, typically only enabled during development.

_logger.LogTrace("Entering method {MethodName}", nameof(GetProducts));

Debug

Information useful for debugging.

_logger.LogDebug("Query returned {Count} products", products.Count);

Information

General application flow events.

_logger.LogInformation("User {UserId} logged in", userId);

Warning

Unexpected but recoverable events.

_logger.LogWarning("Product {ProductId} stock is low: {Stock}", id, stock);

Error

Errors and exceptions that stop the current operation.

_logger.LogError(ex, "Failed to save product {ProductId}", productId);

Critical

Critical failures requiring immediate attention.

_logger.LogCritical("Database connection failed");

Configuring Log Levels

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft.AspNetCore": "Warning",
      "InvenTrack.Controllers": "Debug"
    }
  }
}

{
  "Logging": {
    "LogLevel": {
      "Default": "Debug"
    }
  }
}

Key Takeaways

• Six levels: Trace, Debug, Information, Warning, Error, Critical
• Trace/Debug: Development only
• Information: Normal flow
• Warning: Unexpected but recoverable
• Error: Operation failures
• Critical: Application crashes
• Configure: appsettings.json per environment