File Logging with Rotation¶

This example shows how to configure Logly for file logging with automatic rotation based on file size and time intervals.

Code Example¶

from logly import logger
import time

# Configure for file logging with rotation
logger.configure(level="INFO", color=False)

# Time-based rotation (daily)
logger.add(
    "logs/app.log",
    rotation="daily",  # Rotate daily at midnight
    retention=7,       # Keep 7 days of logs
    date_enabled=True  # Add date to rotated filenames
)

# Size-based rotation
logger.add(
    "logs/large_app.log",
    size_limit="10MB",  # Rotate when file reaches 10MB
    retention=5         # Keep 5 rotated files
)

# Simulate logging activity
for i in range(100):
    logger.info("Processing item {item_id}", item_id=i)
    logger.debug("Debug info for item {item_id}", item_id=i)
    if i % 10 == 0:
        logger.warning("Checkpoint reached: {count} items processed", count=i+1)
    time.sleep(0.01)  # Small delay to simulate work

logger.info("Processing complete")

Configuration Options¶

Time-Based Rotation Options¶

• rotation="daily": Rotate every day at midnight
• rotation="hourly": Rotate every hour
• rotation="minutely": Rotate every minute (for testing)

Size-Based Rotation Options¶

• size_limit="10MB": Rotate when file reaches 10 megabytes
• size_limit="100MB": Rotate at 100MB
• size_limit="1GB": Rotate at 1 gigabyte

Combined Rotation¶

# Rotate daily OR when file reaches 50MB (whichever comes first)
logger.add(
    "logs/app.log",
    rotation="daily",
    size_limit="50MB",
    retention=7
)

Retention Options¶

• Count-based: retention=7 keeps 7 rotated files (oldest are deleted)
• Works with both: Time-based and size-based rotation

Output Files¶

After running, you'll see files like:

app.log (current file):

2025-01-15 10:30:45 | INFO | Processing item 0
2025-01-15 10:30:45 | WARNING | Checkpoint reached: 1 items processed
2025-01-15 10:30:45 | INFO | Processing item 1
...
2025-01-15 10:30:46 | INFO | Processing complete

Directory listing after daily rotation with date_enabled=True:

logs/
├── app.log                    # Current active log file
├── app_2025-01-15.log        # Today's rotated file
├── app_2025-01-14.log        # Yesterday's file
├── app_2025-01-13.log        # Previous day's file
├── app_2025-01-12.log
├── app_2025-01-11.log
├── app_2025-01-10.log
└── app_2025-01-09.log        # 7th day (retention=7 keeps this)
# app_2025-01-08.log          # Deleted (over retention limit)

What happens: - Files rotate automatically based on your configuration - The date_enabled=True parameter adds dates to rotated filenames - Old files beyond the retention limit are automatically deleted - Current logs always go to app.log (or your specified filename)

Key Features Demonstrated¶

• File output: Logs written to files instead of console
• Automatic rotation: Files rotate based on size/time
• Retention policy: Old logs automatically cleaned up
• File and line info: Shows where log calls originated