@dynamic-mock-server/logger

Pino-based logger with pretty formatting and namespacing

Lightweight logger wrapper around Pino with pino-pretty for beautiful terminal output. Provides namespacing for organized logging across different modules.

Features

• 📝 Pino-Based: Built on high-performance Pino logger
• 🎨 Pretty Output: Colorized, readable logs with pino-pretty
• 🏷️ Namespacing: Create child loggers with namespace bindings
• 🎯 Log Levels: Full support for trace, debug, info, warn, error, fatal
• ⚙️ Configurable: Custom log levels and options
• 🚀 Fast: Zero-cost abstractions over Pino

Installation

pnpm add @dynamic-mock-server/logger

Quick Start

Basic Usage

import { Logger } from "@dynamic-mock-server/logger";

// Create logger with default settings
const logger = new Logger();

logger.info("Server started");
logger.debug("Loading configuration");
logger.warn("Deprecation warning");
logger.error("Failed to load file");

With Log Level

import { Logger } from "@dynamic-mock-server/logger";

const logger = new Logger({ level: "debug" });

logger.trace("Very detailed"); // Won't show (below debug)
logger.debug("Debugging info"); // Shows
logger.info("Information"); // Shows

Namespaced Loggers

import { Logger } from "@dynamic-mock-server/logger";

const logger = new Logger();

// Create namespaced loggers
const routesLogger = logger.namespace("routes");
const pluginsLogger = logger.namespace("plugins");

routesLogger.info("Route registered");
// Output: [routes] Route registered

pluginsLogger.info("Plugin loaded");
// Output: [plugins] Plugin loaded

Child Loggers with Bindings

import { Logger } from "@dynamic-mock-server/logger";

const logger = new Logger();

// Create child with custom bindings
const requestLogger = logger.child({ requestId: "abc123", userId: "user1" });

requestLogger.info("Processing request");
// Output includes: requestId: "abc123", userId: "user1"

API Reference

Logger Class

Constructor

constructor(options?: LoggerOptions)

LoggerOptions:

• level?: string - Log level (trace, debug, info, warn, error, fatal). Default: "info"
• options?: pino.LoggerOptions - Additional Pino options

Log Methods

trace(...args: Parameters<LogFn>)

debug(...args: Parameters<LogFn>)

info(...args: Parameters<LogFn>)

warn(...args: Parameters<LogFn>)

error(...args: Parameters<LogFn>)

fatal(...args: Parameters<LogFn>)

Log at different levels.

logger.info("Simple message");
logger.info({ userId: 123 }, "User logged in");
logger.error({ err: error }, "Failed to process");

Utility Methods

child(bindings?: Record<string, unknown>): Logger

Create a child logger with additional bindings.

const childLogger = logger.child({ module: "auth" });
childLogger.info("Authentication successful");

namespace(name: string): Logger

Create a namespaced logger (shorthand for child({ namespace: name })).

const apiLogger = logger.namespace("api");
apiLogger.info("API request received");

get raw(): pino.Logger

Access the underlying Pino logger instance.

const pinoLogger = logger.raw;

Log Levels

Available log levels (in order of severity):

1. trace - Very detailed debugging
2. debug - Detailed debugging
3. info - General information (default)
4. warn - Warnings
5. error - Errors
6. fatal - Fatal errors

Set via environment variable:

LOG_LEVEL=debug npm start

Or via constructor:

const logger = new Logger({ level: "debug" });

Examples

Complete Server Logging

import { Logger } from "@dynamic-mock-server/logger";

const logger = new Logger({ level: process.env.LOG_LEVEL || "info" });

// Module-specific loggers
const serverLogger = logger.namespace("server");
const routesLogger = logger.namespace("routes");
const dbLogger = logger.namespace("database");

serverLogger.info("Starting server on port 3000");
routesLogger.info("Loaded 15 routes");
dbLogger.warn("Connection pool nearing capacity");

Request Logging

import { Logger } from "@dynamic-mock-server/logger";

const logger = new Logger();

function handleRequest(req: Request) {
  const requestLogger = logger.child({
    requestId: req.id,
    method: req.method,
    url: req.url,
  });

  requestLogger.info("Request started");

  try {
    // Process request
    requestLogger.info("Request completed");
  } catch (error) {
    requestLogger.error({ err: error }, "Request failed");
  }
}

Dependencies

• pino - High-performance logger
• pino-pretty - Pretty formatting for development

Related Packages

• @dynamic-mock-server/core - Uses logger for all core operations
• @dynamic-mock-server/config - Respects logLevel config

License

Apache-2.0 © Miguel Martínez