Logging

Instructions

When helping users implement logging in RocsMiddleware services, follow these guidelines:

1. Command-Line Option: Always include --log-dir parameter for specifying log directory path

2. UTF-8 Encoding: All log files must use UTF-8 encoding without BOM

3. Automatic Filename Pattern: Use {ProgramName}_YYYY_MM_DD.log format with automatic date rotation

4. Directory Path Handling: Smart detection - if path has no extension or ends with separator, treat as directory and use directory name as base filename

5. Error Handling: Include console output before logger initialization since logger may fail. Always check if _logger is null in exception handlers.

6. Log Levels: Use LogLevel.Debug with --debug flag, default to LogLevel.Information

7. Thread Safety: The UTF8Writer uses locking for concurrent writes

8. Utf8LoggingExtensions.cs: Copy the reference implementation to project's Services/ directory - provides UTF8Writer, UTF8LoggerProvider, UTF8Logger, and helper methods

Examples

Example 1: Basic Logger Setup

User: Help me add logging to my RocsMiddleware service

Claude: I'll set up the standard UTF-8 file logging pattern:
- Add --log-dir command-line option
- Copy Utf8LoggingExtensions.cs to Services/
- Initialize logger with automatic date-based filename
- Add console output before logger initialization for debugging

[Provides implementation using the Logger Initialization pattern from reference material below]

Example 2: Directory Path Handling

User: Why isn't my log file being created when I specify --log-dir?

Claude: Let me check the directory path handling. The logger should:
- Detect if path is a directory (no extension or ends with separator)
- Use directory name as base filename
- Add date string and .log extension automatically

Common issue: Old Utf8LoggingExtensions.cs without directory detection logic.
Solution: Copy the updated version from skills folder.

[Provides directory detection implementation from reference material below]

Example 3: Error Handling Before Logger Init

User: My program just prints "Error" with no details

Claude: This happens when an exception occurs before logger initialization. I'll add:
- Console.WriteLine at key points (startup, before logger init, after logger init)
- Null check on _logger in exception handler
- Fallback to console output if logger is null

[Provides error handling pattern from reference material below]

Reference Implementation Details

The sections below contain proven working code from RocsMiddleware services that the examples above reference.

Reference Files in This Folder:

• Utf8LoggingExtensions.cs - Complete UTF-8 logger implementation (copy to Services/)

Standard Logging Pattern

All RocsMiddleware services use a consistent logging approach:

1. Command-line option: --log-dir parameter specifies the directory path
2. Automatic filename generation: {ProgramName}_YYYY_MM_DD.log
3. UTF-8 encoding: All log files use UTF-8 encoding
4. Date rotation: Log files automatically rotate daily based on the date

Implementation

Command-Line Option

[Option("log-dir", Required = false, HelpText = "Directory for log files")]
public string? LogDir { get; set; }

Logger Initialization

// Initialize logger with optional log directory
var logLevel = options.Debug ? LogLevel.Debug : LogLevel.Information;
_logger = {Namespace}.Services.Utf8LoggingExtensions.CreateUtf8Logger(
    "{ProgramName}",
    logLevel,
    options.LogDir);

Example Usage

dotnet run -- --log-dir "C:\RI Services\Logs\MyProgram" --other-options

This creates: C:\RI Services\Logs\MyProgram\MyProgram_2025_10_16.log

Directory Path Handling

The UTF8Writer.Init() method automatically detects directory paths and creates properly named log files:

• If path has no extension and ends with a path separator (or exists as a directory), it's treated as a directory
• The directory name becomes the base name for the log file
• Default .log extension is added automatically
• Date string in format YYYY_MM_DD is inserted before the extension

Examples

UTF8LoggingExtensions.cs

All services include a Services/Utf8LoggingExtensions.cs file that provides:

• UTF8Writer class: Low-level UTF-8 file writer with thread-safe locking
• UTF8LoggerProvider: Custom logger provider for Microsoft.Extensions.Logging
• UTF8Logger: ILogger implementation that writes to UTF-8 files
• CreateUtf8Logger(): Helper method to create a configured logger instance
• ConfigureUtf8Logging(): Extension method for ILoggingBuilder

Error Handling

Before Logger Initialization

Since the logger may fail to initialize, always include console output for early errors:

public static async Task Main(string[] args)
{
    try
    {
        Console.WriteLine("{ProgramName} starting...");

        // Parse command line
        CommandLineOptions? options = null;
        Parser.Default.ParseArguments<CommandLineOptions>(args)
            .WithParsed(opts => options = opts)
            .WithNotParsed(errors =>
            {
                Console.WriteLine("Failed to parse command line arguments");
                Environment.Exit(1);
            });

        if (options == null)
        {
            Console.WriteLine("Failed to parse command line options");
            Environment.Exit(1);
            return;
        }

        Console.WriteLine($"Initializing logger with log-dir: {options.LogDir ?? "(null)"}");

        // Initialize logger
        _logger = {Namespace}.Services.Utf8LoggingExtensions.CreateUtf8Logger(
            "{ProgramName}",
            options.Debug ? LogLevel.Debug : LogLevel.Information,
            options.LogDir);

        Console.WriteLine("Logger initialized");

        _logger.LogInformation("{ProgramName} starting");

        // ... rest of program
    }
    catch (Exception ex)
    {
        if (_logger != null)
        {
            _logger.LogError(ex, "{ProgramName} failed: {Message}", ex.Message);
        }
        else
        {
            Console.WriteLine($"{ProgramName} failed: {ex.Message}");
            Console.WriteLine(ex.StackTrace);
        }
        Environment.Exit(1);
    }
}

Log Levels

Standard log levels used across all services:

• LogLevel.Debug: Verbose diagnostic information (use --debug flag)
• LogLevel.Information: General informational messages (default)
• LogLevel.Warning: Warning messages for non-critical issues
• LogLevel.Error: Error messages for failures

Real-World Examples

PriceExtractor

dotnet run -- --pqdir "R:\Outputs\Parquets\poller" --pg "R:\JsonParams\x3rocs_db.json" --log-dir "C:\RI Services\Logs\PriceExtractor" --full

Creates: C:\RI Services\Logs\PriceExtractor\PriceExtractor_2025_10_16.log

PriceDiscountUploader

dotnet run -- --pg "R:/JsonParams/x3rocs_db.json" --log-dir "R:/Logs/PriceDiscounter" --elastic https://rocs-stage-es.ramsden-international.com/ --debug --sphkey1 425073

Creates: R:/Logs/PriceDiscounter/PriceDiscounter_2025_10_16.log

Benefits

1. Consistent naming: All services follow the same {ProgramName}_YYYY_MM_DD.log pattern
2. Automatic rotation: Daily log files without manual intervention
3. UTF-8 encoding: Proper support for international characters
4. Directory-aware: Smart handling of directory vs. file paths
5. Optional logging: Works without --log-dir (console only)
6. Thread-safe: Multiple threads can log simultaneously

Common Issues

No Log File Created

Symptom: Program runs but no log file appears in the specified directory.

Causes:

1. Old version of Utf8LoggingExtensions.cs without directory path handling
2. Logger initialization failing silently

Solution:

• Copy Utf8LoggingExtensions.cs from this skills folder to your project's Services/ directory
• Add console debug output before logger initialization (see Error Handling section above)
• Check that the UTF8Writer.Init() method includes directory detection logic

Program Exits with "Error" and No Details

Symptom: Program outputs just "Error" with no stack trace or details.

Causes:

1. Exception thrown before logger is initialized
2. Exception handler trying to use null logger

Solution:

• Add console output at key points (see Error Handling section)
• Wrap exception handler to check if _logger is null before using it
• Check log file was actually created and contains error details

Related Files

• Utf8LoggingExtensions.cs: Reference implementation included in this folder - copy to your project's Services/ directory
• Command-line parsing: Uses CommandLineParser library
• All services in RocsMiddleware follow this pattern

Notes

• Log files are created on-demand when the first log message is written
• If --log-dir is not specified, logging goes to console only (if enabled)
• Parent directories are created automatically if they don't exist
• Log files are UTF-8 encoded without BOM
• The logger uses Microsoft.Extensions.Logging interfaces for compatibility