Rsyslog Logger

A production-ready Python logging library with professional rsyslog-style formatting, reliable log rotation, and cross-platform compatibility. Designed for system administrators and developers who need robust, operational logging.

🚀 Features

• 📝 Rsyslog-style formatting: Industry-standard syslog format (Jan 1 12:34:56 hostname program[pid]: level: message)
• 🔄 Reliable log rotation: Copy-and-truncate method works even with open file handles (Windows-friendly)
• ⚡ Zero dependencies: No external requirements, uses only Python standard library
• 🌍 Cross-platform: Works seamlessly on Windows, Linux, and macOS
• 🔧 Production-ready: Robust error handling and file operation safety
• 📊 Configurable: Flexible sizing, backup counts, and formatting options
• 🧪 Fully tested: Comprehensive test suite with 25+ tests

📦 Installation

pip install rsyslog-logger

🎯 Quick Start

from rsyslog_logger import setup_logger

# Simple setup with default rsyslog formatting
logger = setup_logger("myapp")
logger.info("Application started")
# Output: Sep 11 20:15:30 hostname myapp[1234]: info: Application started

# Custom log file and level
logger = setup_logger(
    name="myapp",
    log_file="/var/log/myapp.log",
    log_level="DEBUG"
)
logger.debug("Debug information")
logger.error("Something went wrong!")

📖 Usage Examples

Basic Logging

from rsyslog_logger import setup_logger

logger = setup_logger("webapp")

logger.info("User login successful")
logger.warning("High memory usage detected")
logger.error("Database connection failed")
logger.critical("System shutdown initiated")

Custom Configuration

from rsyslog_logger import setup_logger

# Production configuration with custom settings
logger = setup_logger(
    name="production-app",
    log_file="/var/log/production.log",
    log_level="INFO",
    log_format="rsyslog",           # or "simple"
    console_log_level="ERROR",      # Only errors to console
    max_size=20,                    # Rotate at 20MB
    backup_count=10                 # Keep 10 backup files
)

# The logger automatically handles:
# - Log rotation when files get too large (10MB default)
# - Keeps 5 backup files by default
# - Proper file handle management
# - Cross-platform path handling

Using Different Formatters

# Rsyslog format (default)
logger = setup_logger("app", log_format="rsyslog")
logger.info("Hello world")
# Sep 11 20:15:30 hostname app[1234]: info: Hello world

# Simple format
logger = setup_logger("app", log_format="simple")
logger.info("Hello world")
# 2025-09-11 20:15:30 - INFO - Hello world

Advanced Usage with Manual Rotation

from rsyslog_logger import setup_logger, rotate_log_file, cleanup_old_log_files

logger = setup_logger("advanced-app", "/var/log/app.log")

# Manual log rotation (automatic rotation happens by size)
rotate_log_file("/var/log/app.log", force=True)

# Custom cleanup (keep only 3 backup files)
cleanup_old_log_files("/var/log/app.log", backup_count=3)

Exception Logging

logger = setup_logger("error-handler")

try:
    result = 10 / 0
except ZeroDivisionError:
    logger.exception("Division error occurred")
    # Automatically includes full traceback

⚙️ Configuration Options

setup_logger() Parameters

Parameter	Type	Default	Description
name	str	"Rsyslog-Logger"	Logger name (appears in log messages)
log_file	str	"Rsyslog-Logger.log"	Log file path (None for console only)
log_level	str	"INFO"	Logging level (DEBUG, INFO, WARNING, ERROR, CRITICAL)
log_format	str	"rsyslog"	Format style ("rsyslog" or "simple")
console_log_level	str	"INFO"	Separate log level for console output
max_size	int/float	10	Maximum log file size in MB before rotation
backup_count	int	5	Number of backup log files to keep

Log Rotation Settings

The logger automatically rotates files when they exceed 10MB by default. You can customize this:

from rsyslog_logger import SizeRotatingFileHandler

# Custom rotation size (5MB)
handler = SizeRotatingFileHandler(
    "/var/log/app.log",
    max_size=5  # 5MB
)

Cleanup Settings

from rsyslog_logger import cleanup_old_log_files

# Keep only 10 backup files
cleanup_old_log_files("/var/log/app.log", backup_count=10)

# Remove all backups
cleanup_old_log_files("/var/log/app.log", backup_count=0)

🏗️ Architecture

The library consists of several key components:

• setup_logger(): Main entry point for logger configuration
• SizeRotatingFileHandler: Custom file handler with size-based rotation
• RsyslogFormatter: Professional syslog-style message formatting
• rotate_log_file(): Manual log rotation using copy-and-truncate
• cleanup_old_log_files(): Backup file management with configurable retention

Why Copy-and-Truncate?

Unlike traditional rotation methods that move files, this library uses copy-and-truncate rotation:

✅ Works with open file handles (no application restart needed) ✅ Windows compatible (no file locking issues) ✅ Safe for production (no log loss during rotation) ✅ Process-agnostic (works regardless of file handle state)

📡 Remote Syslog Integration

Configuring rsyslogd for Remote Logging

To forward logs to a remote syslog daemon using the omfwd module, add the following to your /etc/rsyslog.conf or create a new file in /etc/rsyslog.d/:

# Forward all logs to remote syslog server
*.* @@remote-syslog-server:514

# Forward only specific facility/priority
local0.* @@remote-syslog-server:514

# Forward with specific format (optional)
$ActionForwardDefaultTemplate RSYSLOG_TraditionalForwardFormat
*.* @@remote-syslog-server:514

Protocol Options:

• @@ - TCP (reliable, recommended for production)
• @ - UDP (faster, may lose messages)

Example rsyslogd Configuration

# /etc/rsyslog.d/50-remote.conf

# Load omfwd module
$ModLoad omfwd

# Forward application logs to remote server
local0.* @@log-server.example.com:514

# Optional: Forward to multiple servers
local0.* @@primary-log-server:514
local0.* @@backup-log-server:514

# Restart rsyslogd after configuration changes
# systemctl restart rsyslog

Monitoring Log Files with imfile Module

Ubuntu/Debian systems can monitor specific log files and forward them through syslog using the imfile module:

# /etc/rsyslog.d/60-myapp.conf

# Load imfile module
$ModLoad imfile

# Monitor application log file
$InputFileName /var/log/myapp.log
$InputFileTag myapp:
$InputFileStateFile stat-myapp
$InputFileSeverity info
$InputFileFacility local0
$InputRunFileMonitor

# Forward to remote server
local0.* @@remote-syslog-server:514

After adding the configuration:

sudo systemctl restart rsyslog

Property-Based Filtering and Routing

rsyslog supports advanced filtering based on message properties like $programname. This is perfect for routing specific application logs:

# /etc/rsyslog.d/50-app-routing.conf

# Route messages by program name to specific files
if $programname == 'myapp' then /var/log/myapp.log
& stop

# Route by program name to remote server
if $programname == 'critical-app' then @@remote-syslog-server:514
if $programname == 'critical-app' then /var/log/critical-app.log
& stop

# Multiple conditions
if $programname == 'webapp' and $msg contains 'ERROR' then {
    @@error-server:514
    /var/log/webapp-errors.log
    stop
}

# Default catch-all (messages not handled above)
*.* /var/log/syslog

Key Syntax:

• if $programname == 'name' then action - Conditional routing
• & stop - Stop processing, prevent further rules
• stop - Modern syntax (same as & stop)
• $msg contains 'text' - Message content filtering
• and, or - Logical operators

🧪 Testing

Run the comprehensive test suite:

# Install test dependencies
pip install pytest pytest-cov

# Run tests
pytest

# Run with coverage
pytest --cov=rsyslog_logger --cov-report=html

The test suite includes:

• Rotation testing: Size limits, backup creation, sequential numbering
• Format validation: Rsyslog format compliance, timestamp accuracy
• Cleanup testing: Backup count limits, file sorting, error handling
• Cross-platform testing: Windows and Linux compatibility
• Error resilience: Permission errors, missing files, edge cases

🤝 Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

Development Setup

# Clone the repository
git clone https://github.com/Oratorian/rsyslog-logger.git
cd rsyslog-logger

# Install development dependencies
pip install -e .
pip install pytest pytest-cov pytest-mock

# Run tests
pytest

Code Quality

• Follow PEP 8 style guidelines
• Add tests for new functionality
• Update documentation for API changes
• Ensure cross-platform compatibility

📄 License

This project is licensed under the MIT License - see the LICENSE file for details.

🔗 Links

• PyPI Package: https://pypi.org/project/rsyslog-logger/
• Source Code: https://github.com/Oratorian/rsyslog-logger
• Issue Tracker: https://github.com/Oratorian/rsyslog-logger/issues
• Documentation: https://github.com/Oratorian/rsyslog-logger/blob/main/README.md

🎉 Why Choose Rsyslog Logger?

For System Administrators:

• Professional syslog format integrates with existing log management
• Reliable rotation prevents disk space issues
• Cross-platform compatibility for mixed environments
• Zero-dependency deployment simplifies installation

For Developers:

• Production-ready out of the box
• Comprehensive error handling
• Clean, documented API
• Extensive test coverage ensures reliability

For DevOps Teams:

• Operational logging best practices built-in
• Configurable retention policies
• Performance optimized for high-throughput scenarios
• Container and cloud-friendly

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