Logger Implementations

MSR provides multiple logger implementations to suit different use cases, from development to production environments.

Available Loggers

ConsoleLogger

The default logger that outputs all messages to the console using standard console.* methods. Perfect for development and debugging.

Best for: Local development, debugging, interactive environments

SilentLogger

Suppresses all log output completely. Ideal for testing and scenarios where logging is not desired.

Best for: Unit tests, CI/CD pipelines, silent operations

FileLogger

Writes logs to files with automatic rotation based on file size. Includes timestamp support and configurable backup retention.

Best for: Production environments, persistent logging, audit trails

CompositeLogger

Forwards log messages to multiple logger implementations simultaneously. Enables logging to multiple destinations (console + file, file + cloud, etc.) with dynamic logger management.

Best for: Multi-destination logging, production environments, flexible logging strategies

Logger Comparison

Choose the right logger for your environment:

Logger Output Performance Use Case Best For
ConsoleLogger 🖥️ Console 🟢 Fast Development Local dev
SilentLogger ❌ None 🟢 Fastest Testing Unit tests
FileLogger 📄 Files 🟡 Medium Production Audit logs
CompositeLogger 🔀 Multiple 🟡 Medium Production Multi-dest
Cloud Loggers ☁️ Cloud 🟡 Network Production Distributed

Feature Matrix

Feature Console Silent File Composite Cloud
Timestamps ✅ N/A ✅ ✅ ✅
Log Levels ✅ N/A ✅ ✅ ✅
Rotation ❌ N/A ✅ Depends ✅
Async ❌ ❌ ✅ Depends ✅
Persistence ❌ ❌ ✅ Depends ✅
Searchable ❌ ❌ ⚠️ Limited Depends ✅
Cost Free Free Free Free 💰 Paid

Recommended for Production: Use CompositeLogger with FileLogger + Cloud Logger for redundancy and better observability.

Cloud Logger Guide

Guide for implementing cloud logging services (AWS CloudWatch, Google Cloud Logging, Azure, Datadog, etc.).

Best for: Centralized logging, multi-instance deployments, cloud-native applications

Note: These implementations are not included in MSR but serve as production-ready examples and starting points.

Log Level Control

MSR v0.6.0+ includes automatic log level filtering through the LevelAwareLogger wrapper. When you provide a logger to MigrationScriptExecutor, it’s automatically wrapped to filter messages based on your configured log level.

Automatic Wrapping

All loggers are automatically wrapped with level-aware filtering:

// Your logger is automatically wrapped with log level filtering
const executor = new MigrationScriptExecutor({ handler }, {
    logLevel: 'error'  // Only errors will be shown
}, {
    logger: new ConsoleLogger()  // Automatically wrapped
});

Log Levels

Control output verbosity with four levels (each includes higher priority levels):

Level Shows Environment
error Errors only Production (quiet)
warn Warnings + Errors Production (monitoring)
info Info + Warnings + Errors Default (standard operation)
debug All logs Development (verbose)

Configuration

Set via configuration object or environment variable:

// Programmatic
config.logLevel = 'debug';

// Environment variable
export MSR_LOG_LEVEL=error

See Also:

Quick Comparison

Feature ConsoleLogger SilentLogger FileLogger CompositeLogger
Output Location Console None File system Multiple destinations
Rotation N/A N/A ✅ Size-based Depends on child loggers
Timestamps ❌ N/A ✅ Configurable Depends on child loggers
Configuration None None Extensive Dynamic (add/remove loggers)
Performance Fast Fastest Moderate Depends on number of loggers
Best Use Case Development Testing Production Multi-destination logging

Creating Custom Loggers

All loggers implement the ILogger interface. See the Custom Logging Guide for detailed examples of creating your own logger implementations.

Next Steps

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