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examples.py
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318 lines (244 loc) · 9.55 KB
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import logging
import json
from datetime import datetime, timezone
import os
from logging.handlers import RotatingFileHandler, TimedRotatingFileHandler
logger = logging.getLogger('my_app')
logger.setLevel(logging.DEBUG)
console_handler = logging.StreamHandler()
console_handler.setLevel(logging.INFO)
file_handler = logging.FileHandler('app.log')
file_handler.setLevel(logging.DEBUG)
formatter = logging.Formatter(
'%(asctime)s - %(name)s - %(levelname)s - %(message)s'
)
console_handler.setFormatter(formatter)
file_handler.setFormatter(formatter)
logger.addHandler(console_handler)
logger.addHandler(file_handler)
logger.debug('This is a debug message')
logger.info('Application started')
logger.warning('Disk space running low')
logger.error('Failed to connect to database')
logger.critical('System shutting down')
###
logger = logging.getLogger('payment_processor')
logger.setLevel(logging.DEBUG)
handler = logging.StreamHandler()
handler.setFormatter(logging.Formatter('%(levelname)s: %(message)s'))
logger.addHandler(handler)
def process_payment(user_id, amount):
logger.debug(f'Starting payment processing for user {user_id}')
if amount <= 0:
logger.error(f'Invalid payment amount: {amount}')
return False
logger.info(f'Processing ${amount} payment for user {user_id}')
if amount > 10000:
logger.warning(f'Large transaction detected: ${amount}')
try:
# Simulate payment processing
success = charge_card(user_id, amount)
if success:
logger.info(f'Payment successful for user {user_id}')
return True
else:
logger.error(f'Payment failed for user {user_id}')
return False
except Exception as e:
logger.critical(f'Payment system crashed: {e}', exc_info=True)
return False
def charge_card(user_id, amount):
# Simulated payment logic
return True
process_payment(12345, 150.00)
process_payment(12345, 15000.00)
# logging exceptions
import json
logger = logging.getLogger('api_handler')
logger.setLevel(logging.DEBUG)
handler = logging.FileHandler('errors.log')
formatter = logging.Formatter(
'%(asctime)s - %(name)s - %(levelname)s - %(message)s'
)
handler.setFormatter(formatter)
logger.addHandler(handler)
def fetch_user_data(user_id):
logger.info(f'Fetching data for user {user_id}')
try:
# Simulate API call
response = call_external_api(user_id)
data = json.loads(response)
logger.debug(f'Received data: {data}')
return data
except json.JSONDecodeError as e:
logger.error(
f'Failed to parse JSON for user {user_id}: {e}',
exc_info=True
)
return None
except ConnectionError as e:
logger.error(
f'Network error while fetching user {user_id}',
exc_info=True
)
return None
except Exception as e:
logger.critical(
f'Unexpected error in fetch_user_data: {e}',
exc_info=True
)
raise
def call_external_api(user_id):
# Simulated API response
return '{"id": ' + str(user_id) + ', "name": "John"}'
fetch_user_data(123)
# from logger_config
from logger_config import setup_logger
logger = setup_logger(__name__)
def calculate_discount(price, discount_percent):
logger.debug(f'Calculating discount: {price} * {discount_percent}%')
if discount_percent < 0 or discount_percent > 100:
logger.warning(f'Invalid discount percentage: {discount_percent}')
discount_percent = max(0, min(100, discount_percent))
discount = price * (discount_percent / 100)
final_price = price - discount
logger.info(f'Applied {discount_percent}% discount: ${price} -> ${final_price}')
return final_price
calculate_discount(100, 20)
calculate_discount(100, 150)
# Structured Logging with Context
class ContextLogger:
"""Logger wrapper that adds contextual information to all log messages"""
def __init__(self, name, context=None):
self.logger = logging.getLogger(name)
self.context = context or {}
handler = logging.StreamHandler()
formatter = logging.Formatter('%(message)s')
handler.setFormatter(formatter)
# Check if handler already exists to avoid duplicate handlers
if not any(isinstance(h, logging.StreamHandler) and h.formatter._fmt == '%(message)s' for h in self.logger.handlers):
self.logger.addHandler(handler)
self.logger.setLevel(logging.DEBUG)
def _format_message(self, message, level, extra_context=None):
"""Format message with context as JSON"""
log_data = {
'timestamp': datetime.now(timezone.utc).isoformat(),
'level': level,
'message': message,
'context': {**self.context, **(extra_context or {})}
}
return json.dumps(log_data)
def debug(self, message, **kwargs):
self.logger.debug(self._format_message(message, 'DEBUG', kwargs))
def info(self, message, **kwargs):
self.logger.info(self._format_message(message, 'INFO', kwargs))
def warning(self, message, **kwargs):
self.logger.warning(self._format_message(message, 'WARNING', kwargs))
def error(self, message, **kwargs):
self.logger.error(self._format_message(message, 'ERROR', kwargs))
def process_order(order_id, user_id):
logger = ContextLogger(__name__, context={
'order_id': order_id,
'user_id': user_id
})
logger.info('Order processing started')
try:
items = fetch_order_items(order_id)
logger.info('Items fetched', item_count=len(items))
total = calculate_total(items)
logger.info('Total calculated', total=total)
if total > 1000:
logger.warning('High value order', total=total, flagged=True)
return True
except Exception as e:
logger.error('Order processing failed', error=str(e))
return False
def fetch_order_items(order_id):
return [{'id': 1, 'price': 50}, {'id': 2, 'price': 75}]
def calculate_total(items):
return sum(item['price'] for item in items)
process_order('ORD-12345', 'USER-789')
# Rotating log files
def setup_rotating_logger(name):
logger = logging.getLogger(name)
logger.setLevel(logging.DEBUG)
# Size-based rotation: rotate when file reaches 10MB
size_handler = RotatingFileHandler(
'app_size_rotation.log',
maxBytes=10 * 1024 * 1024, # 10 MB
backupCount=5 # Keep 5 old files
)
size_handler.setLevel(logging.DEBUG)
# Time-based rotation: rotate daily at midnight
time_handler = TimedRotatingFileHandler(
'app_time_rotation.log',
when='midnight',
interval=1,
backupCount=7 # Keep 7 days
)
time_handler.setLevel(logging.INFO)
formatter = logging.Formatter(
'%(asctime)s - %(name)s - %(levelname)s - %(message)s'
)
size_handler.setFormatter(formatter)
time_handler.setFormatter(formatter)
logger.addHandler(size_handler)
logger.addHandler(time_handler)
return logger
logger = setup_rotating_logger('rotating_app')
for i in range(1000):
logger.info(f'Processing record {i}')
logger.debug(f'Record {i} details: completed in {i * 0.1}ms')
# diff envs
def configure_environment_logger(app_name):
"""Configure logger based on environment"""
environment = os.getenv('APP_ENV', 'development')
logger = logging.getLogger(app_name)
# Clear existing handlers
logger.handlers = []
if environment == 'development':
# Development: verbose console output
logger.setLevel(logging.DEBUG)
handler = logging.StreamHandler()
handler.setLevel(logging.DEBUG)
formatter = logging.Formatter(
'%(levelname)s - %(name)s - %(funcName)s:%(lineno)d - %(message)s'
)
handler.setFormatter(formatter)
logger.addHandler(handler)
elif environment == 'staging':
# Staging: detailed file logs + important console messages
logger.setLevel(logging.DEBUG)
file_handler = logging.FileHandler('staging.log')
file_handler.setLevel(logging.DEBUG)
file_formatter = logging.Formatter(
'%(asctime)s - %(name)s - %(levelname)s - %(funcName)s - %(message)s'
)
file_handler.setFormatter(file_formatter)
console_handler = logging.StreamHandler()
console_handler.setLevel(logging.WARNING)
console_formatter = logging.Formatter('%(levelname)s: %(message)s')
console_handler.setFormatter(console_formatter)
logger.addHandler(file_handler)
logger.addHandler(console_handler)
elif environment == 'production':
# Production: structured logs, errors only to console
logger.setLevel(logging.INFO)
file_handler = logging.handlers.RotatingFileHandler(
'production.log',
maxBytes=50 * 1024 * 1024, # 50 MB
backupCount=10
)
file_handler.setLevel(logging.INFO)
file_formatter = logging.Formatter(
'{"timestamp": "%(asctime)s", "level": "%(levelname)s", '
'"logger": "%(name)s", "message": "%(message)s"}'
)
file_handler.setFormatter(file_formatter)
console_handler = logging.StreamHandler()
console_handler.setLevel(logging.ERROR)
console_formatter = logging.Formatter('%(levelname)s: %(message)s')
console_handler.setFormatter(console_formatter)
logger.addHandler(file_handler)
logger.addHandler(console_handler)
return logger