Log Rotation

Log rotation is an important mechanism for managing log file size and quantity. pretty-loguru provides flexible and powerful rotation strategies.

🎯 Configuration Template Rotation Presets

Pretty-Loguru provides predefined rotation configuration templates through ConfigTemplates to quickly set up common time-based rotation strategies:

Daily Rotation

python

from pretty_loguru import ConfigTemplates

# Daily rotation configuration
config = ConfigTemplates.daily()
logger = config.apply_to("daily_app")

# Configuration includes:
# - rotation: "00:00" (rotates at midnight daily)
# - retention: "30 days" (keeps logs for 30 days)
# - Current filename: [component]daily_latest.temp.log
# - Rotated compressed filename: [component]YYYYMMDD.log

Hourly Rotation

python

# Hourly rotation configuration
config = ConfigTemplates.hourly()
logger = config.apply_to("hourly_app")

# Configuration includes:
# - rotation: "1 hour" (rotates every hour)
# - retention: "7 days" (keeps logs for 7 days)
# - Current filename: [component]hourly_latest.temp.log
# - Rotated compressed filename: [component]YYYYMMDD_HH.log

Weekly Rotation

python

# Weekly rotation configuration
config = ConfigTemplates.weekly()
logger = config.apply_to("weekly_app")

# Configuration includes:
# - rotation: "monday" (rotates every Monday)
# - retention: "12 weeks" (keeps logs for 12 weeks)
# - Current filename: [component]weekly_latest.temp.log
# - Rotated compressed filename: [component]week_YYYYWNN.log

Monthly Rotation

python

# Monthly rotation configuration
config = ConfigTemplates.monthly()
logger = config.apply_to("monthly_app")

# Configuration includes:
# - rotation: "1 month" (rotates monthly)
# - retention: "12 months" (keeps logs for 12 months)
# - Current filename: [component]monthly_latest.temp.log
# - Rotated compressed filename: [component]YYYYMM.log

Minute Rotation

python

# Minute rotation configuration (suitable for high-frequency testing)
config = ConfigTemplates.minute()
logger = config.apply_to("minute_app")

# Configuration includes:
# - rotation: "1 minute" (rotates every minute)
# - retention: "24 hours" (keeps logs for 24 hours)
# - Current filename: [component]minute_latest.temp.log
# - Rotated compressed filename: [component]YYYYMMDD_HHMM.log

File Naming Rules

Time-based rotation presets use fixed filenames, renaming based on time range only during rotation:

Preset Type	Current Filename	Rotated Filename Format	Rotated Example
daily	`[{name}]daily_latest.temp.log`	`[{name}]{date}.log`	`[myapp]20250113.log`
hourly	`[{name}]hourly_latest.temp.log`	`[{name}]{date}_{hour}.log`	`[myapp]20250113_14.log`
weekly	`[{name}]weekly_latest.temp.log`	`[{name}]week_{year}W{week_num}.log`	`[myapp]week_2025W03.log`
monthly	`[{name}]monthly_latest.temp.log`	`[{name}]{year}{month}.log`	`[myapp]202501.log`
minute	`[{name}]minute_latest.temp.log`	`[{name}]{date}_{hour}{minute}.log`	`[myapp]20250113_1430.log`

Note:

The currently active log file uses the xxx_latest.temp.log format
When rotation is triggered, the file is renamed based on the time range it covers
Example: [myapp]daily_latest.temp.log becomes [myapp]20250113.log when rotated at midnight

Custom Rotation Configuration

You can customize based on preset configurations:

python

# Customize daily rotation
custom_daily = ConfigTemplates.daily()
custom_daily.update(
    retention="60 days",     # Keep for 60 days instead of 30
    compression="gz"         # Use gzip compression
)
logger = custom_daily.apply_to("custom_app")

🔄 Rotation Strategies

Size-Based Rotation

Rotate when file reaches a certain size:

python

from pretty_loguru import create_logger

# Rotate when file reaches 10MB
logger = create_logger(
    "app",
    log_path="logs",
    rotation="10 MB"
)

# Other size units
logger = create_logger("app", rotation="100 KB")  # 100 kilobytes
logger = create_logger("app", rotation="1 GB")   # 1 gigabyte

Time-Based Rotation

Rotate at specific time intervals:

python

# Daily rotation at midnight
logger = create_logger("app", rotation="00:00")

# Rotate every 6 hours
logger = create_logger("app", rotation="6 hours")

# Rotate at specific time
from datetime import time
logger = create_logger("app", rotation=time(2, 0))  # 2:00 AM

# Rotate on specific weekday
logger = create_logger("app", rotation="monday")  # Every Monday
logger = create_logger("app", rotation="friday at 18:00")  # Friday 6 PM

Custom Rotation Function

Create custom rotation logic:

python

def should_rotate(message, file):
    """Custom rotation logic"""
    # Rotate if file is larger than 50MB or it's midnight
    file_size = file.tell()
    current_hour = message.record["time"].hour
    
    return file_size > 50 * 1024 * 1024 or current_hour == 0

logger = create_logger(
    "app",
    rotation=should_rotate
)

📦 Retention Policies

Time-Based Retention

Keep logs for a specific duration:

python

# Keep logs for 30 days
logger = create_logger("app", retention="30 days")

# Other time units
logger = create_logger("app", retention="1 week")
logger = create_logger("app", retention="3 months")
logger = create_logger("app", retention="1 year")

Count-Based Retention

Keep a specific number of log files:

python

# Keep only the 10 most recent log files
logger = create_logger("app", retention=10)

Custom Retention Function

Create custom retention logic:

python

from datetime import datetime, timedelta

def cleanup_old_logs(path):
    """Keep logs from current month only"""
    file_date = datetime.fromtimestamp(path.stat().st_mtime)
    current_month = datetime.now().month
    
    return file_date.month != current_month

logger = create_logger("app", retention=cleanup_old_logs)

🗜️ Compression

Built-in Compression Formats

python

# ZIP compression
logger = create_logger("app", compression="zip")

# GZIP compression
logger = create_logger("app", compression="gz")

# BZ2 compression
logger = create_logger("app", compression="bz2")

# TAR compression
logger = create_logger("app", compression="tar")

# TAR.GZ compression
logger = create_logger("app", compression="tar.gz")

Custom Compression Function

python

import gzip
import shutil

def custom_compress(path):
    """Custom compression with high compression level"""
    gz_path = f"{path}.gz"
    
    with open(path, 'rb') as f_in:
        with gzip.open(gz_path, 'wb', compresslevel=9) as f_out:
            shutil.copyfileobj(f_in, f_out)
    
    # Remove original file
    path.unlink()

logger = create_logger("app", compression=custom_compress)

🎯 Common Patterns

Production Setup

python

# Production configuration with daily rotation
prod_logger = create_logger(
    "production_app",
    log_path="/var/log/myapp",
    rotation="00:00",         # Rotate at midnight
    retention="90 days",      # Keep 3 months
    compression="gz"          # Compress old logs
)

High-Volume Logging

python

# For applications with high log volume
high_volume_logger = create_logger(
    "high_volume_app",
    log_path="logs",
    rotation="100 MB",        # Size-based rotation
    retention=20,             # Keep 20 files
    compression="gz",         # Compress immediately
    enqueue=True             # Async logging
)

Development Setup

python

# Development with frequent rotation for testing
dev_logger = create_logger(
    "dev_app",
    log_path="logs/dev",
    rotation="10 MB",         # Small files
    retention="3 days",       # Short retention
    compression=None          # No compression
)

📊 Rotation Examples

Combined Strategies

python

from datetime import time

# Rotate daily at 2 AM or when file reaches 100MB
def combined_rotation(message, file):
    # Check time
    current_time = message.record["time"]
    is_2am = current_time.hour == 2 and current_time.minute == 0
    
    # Check size
    is_large = file.tell() > 100 * 1024 * 1024
    
    return is_2am or is_large

logger = create_logger(
    "app",
    rotation=combined_rotation,
    retention="30 days"
)

Environment-Based Rotation

python

import os

def get_rotation_config():
    env = os.getenv("ENVIRONMENT", "development")
    
    if env == "production":
        return {
            "rotation": "00:00",      # Daily
            "retention": "90 days",   # 3 months
            "compression": "gz"
        }
    elif env == "staging":
        return {
            "rotation": "100 MB",     # Size-based
            "retention": "30 days",   # 1 month
            "compression": "zip"
        }
    else:  # development
        return {
            "rotation": "10 MB",      # Small files
            "retention": "7 days",    # 1 week
            "compression": None
        }

config = get_rotation_config()
logger = create_logger("app", **config)

🔍 Best Practices

Choose Appropriate Strategy: Use time-based for predictable patterns, size-based for variable log volume
Consider Disk Space: Set retention policies based on available storage
Use Compression: Enable compression for long-term storage
Monitor Performance: Large uncompressed logs can impact performance
Test Rotation: Verify rotation works as expected in development

Configuration Guide - Advanced configuration options
Production Guide - Production best practices
API Reference - Complete rotation API

Log Rotation ​

🎯 Configuration Template Rotation Presets ​

Daily Rotation ​

Hourly Rotation ​

Weekly Rotation ​

Monthly Rotation ​

Minute Rotation ​

File Naming Rules ​

Custom Rotation Configuration ​

🔄 Rotation Strategies ​

Size-Based Rotation ​

Time-Based Rotation ​

Custom Rotation Function ​

📦 Retention Policies ​

Time-Based Retention ​

Count-Based Retention ​

Custom Retention Function ​

🗜️ Compression ​

Built-in Compression Formats ​

Custom Compression Function ​

🎯 Common Patterns ​

Production Setup ​

High-Volume Logging ​

Development Setup ​

📊 Rotation Examples ​

Combined Strategies ​

Environment-Based Rotation ​

🔍 Best Practices ​

🔗 Related Resources ​

Log Rotation

🎯 Configuration Template Rotation Presets

Daily Rotation

Hourly Rotation

Weekly Rotation

Monthly Rotation

Minute Rotation

File Naming Rules

Custom Rotation Configuration

🔄 Rotation Strategies

Size-Based Rotation

Time-Based Rotation

Custom Rotation Function

📦 Retention Policies

Time-Based Retention

Count-Based Retention

Custom Retention Function

🗜️ Compression

Built-in Compression Formats

Custom Compression Function

🎯 Common Patterns

Production Setup

High-Volume Logging

Development Setup

📊 Rotation Examples

Combined Strategies

Environment-Based Rotation

🔍 Best Practices

🔗 Related Resources