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Tags

Tags allow you to categorize and organize your logs for easier filtering and analysis. Use tags to group related logs by feature, module, or any custom criteria.

Adding Tags

Use the tags property in the options object:

JavaScript
// Add multiple tags
Log.info('Database query completed', {
    tags: ['performance', 'database']
});

// Single tag
Log.warn('Failed login attempt', {
    tags: ['authentication']
});

// Tags with context
Log.error('External API call failed', {
    tags: ['api', 'external'],
    context: { endpoint: '/payments' }
}, error);

Common Tag Categories

Feature-Based Tags

JavaScript
// Authentication feature
Log.info('Login attempt successful', {
    tags: ['authentication', 'security']
});

// Payment processing
Log.error('Payment gateway timeout', {
    tags: ['payment', 'transaction']
});

// Database operations
Log.warn('Slow query detected', {
    tags: ['database', 'performance']
});

Component-Based Tags

JavaScript
// Cache operations
Log.info('Cache entry expired', {
    tags: ['cache', 'redis']
});

// External APIs
Log.error('External service unavailable', {
    tags: ['api', 'external', 'payment-gateway']
});

// Background jobs
Log.info('Email processing completed', {
    tags: ['background-job', 'email']
});

Express.js Integration

JavaScript
app.post('/api/orders', async (req, res) => {
    Log.info('Order creation started', {
        tags: ['api', 'orders', 'create'],
        context: { customerId: req.body.customerId }
    });
    
    try {
        const order = await orderService.create(req.body);
        
        Log.info('Order created successfully', {
            tags: ['api', 'orders', 'success'],
            context: { orderId: order.id }
        });
        
        res.json(order);
    } catch (error) {
        Log.error('Order creation failed', {
            tags: ['api', 'orders', 'error']
        }, error);
        
        res.status(500).json({ error: 'Failed to create order' });
    }
});

Tag Conventions

Naming Standards

JavaScript
// ✅ Good - Lowercase with hyphens
Log.info('Profile updated successfully', {
    tags: ['user-management', 'profile']
});

// ✅ Good - Simple and clear
Log.warn('Slow query detected', {
    tags: ['database', 'performance']
});

// ❌ Avoid - Inconsistent casing and spaces
Log.info('Profile updated', {
    tags: ['UserManagement', 'PROFILE']
});

Filtering and Analysis

Tags make it easy to filter and analyze logs:

JavaScript
// All payment-related logs can be filtered by "payment" tag
Log.info('Payment processing started', {
    tags: ['payment', 'gateway']
});

Log.warn('Payment retry attempt', {
    tags: ['payment', 'retry']
});

Log.error('Payment processing failed', {
    tags: ['payment', 'error']
});

Best Practices

Best Practices

  • Use lowercase with hyphens for consistency (e.g., "user-management")
  • Keep tags short and meaningful
  • Use multiple tags for better filtering capabilities
  • Document your tagging strategy for the team
  • Combine tags with metadata and context for comprehensive logging

Next Steps

Previous
Metadata & Context
Next
Error Logging