@yigityalim/logger

Structured logging package.

Features

• ✅ Log Levels: debug, info, warn, error
• ✅ Multiple Formatters: JSON, Pretty, Structured
• ✅ Context Propagation: Child loggers with inherited context
• ✅ Performance Monitoring: Track operation duration
• ✅ Log Aggregation: Collect and analyze logs
• ✅ Log Retention: Automatic cleanup with policies
• ✅ File Transport: Write logs to files with rotation
• ✅ Sentry Integration: Error tracking for Next.js and Expo
• ✅ Environment-Aware: Auto-configures based on NODE_ENV
• ✅ Type-Safe: Full TypeScript support
• ✅ Zero Config: Works out of the box

Installation

# Already available in monorepo
import { createLogger } from '@yigityalim/logger';

Usage

Basic Usage

import { createLogger } from '@yigityalim/logger';

const logger = createLogger({
  name: 'api',
});

logger.info('Server started', { port: 3000 });
logger.error('Database error', new Error('Connection failed'));

With Context (Child Loggers)

const logger = createLogger({ name: 'api' });

// Create child logger with context
const userLogger = logger.child({ userId: 'user-123' });

userLogger.info('User logged in');
// Output: [timestamp] [INFO] User logged in context={"userId":"user-123"}

userLogger.info('Profile updated', { field: 'email' });
// Output: [timestamp] [INFO] Profile updated context={"userId":"user-123"} metadata={"field":"email"}

Log Levels

logger.debug('Debug message');  // Only in development
logger.info('Info message');    // General information
logger.warn('Warning message'); // Warning
logger.error('Error message', new Error('Something went wrong'));

Custom Configuration

const logger = createLogger({
  name: 'api',
  level: 'info',      // Minimum log level
  format: 'json',     // json | pretty | structured
  enabled: true,      // Enable/disable logging
  context: {          // Default context
    service: 'api',
    version: '1.0.0',
  },
});

Formatters

Pretty (Development)

17:32:45.123 INFO  Server started [{"port":3000}]

JSON (Production)

{"timestamp":"2025-01-30T17:32:45.123Z","level":"info","message":"Server started","metadata":{"port":3000}}

Structured

[2025-01-30T17:32:45.123Z] [INFO] Server started metadata={"port":3000}

Environment Variables

NODE_ENV=production  # Auto-selects JSON format and 'info' level
NODE_ENV=development # Auto-selects Pretty format and 'debug' level

Examples

API Server

import { createLogger } from '@yigityalim/logger';

const logger = createLogger({ name: 'api' });

app.listen(3000, () => {
  logger.info('Server started', { port: 3000 });
});

app.use((err, req, res, next) => {
  logger.error('Request failed', err);
  res.status(500).json({ error: 'Internal server error' });
});

Job Processing

const logger = createLogger({ name: 'jobs' });

async function processJob(jobId: string) {
  const jobLogger = logger.child({ jobId });
  
  jobLogger.info('Job started');
  
  try {
    // Process job
    jobLogger.info('Job completed');
  } catch (error) {
    jobLogger.error('Job failed', error);
  }
}

User Actions

const logger = createLogger({ name: 'app' });

function handleUserAction(userId: string, action: string) {
  const userLogger = logger.child({ userId });
  
  userLogger.info('User action', { action });
}

Best Practices

1. Use Child Loggers: Create child loggers with context for better traceability
2. Include Metadata: Add relevant metadata to log entries
3. Use Appropriate Levels:
   • debug: Detailed debugging information
   • info: General informational messages
   • warn: Warning messages
   • error: Error messages with stack traces
4. Sanitize Sensitive Data: Never log passwords, tokens, or PII

License

MIT