logger

Generic logger with integrations for e.g. Sentry

Features

• Multiple transport support (console, files, Sentry)
• Winston-based logging with custom transports
• Safe JSON serialization (handles circular references, deep objects, functions)
• Stackdriver/Google Cloud Logging compatible
• Automatic exception and rejection handling
• Configurable log levels per transport
• Production-ready error tracking with Sentry integration

Quick Start

import makeLogger from '@trojs/logger';

const logger = makeLogger({
  level: 'info', 
  service: 'user-service',
  loggers: [
    {
      type: 'console'
    },
    {
      type: 'sentry',
      level: 'error',
      location: 'https://12345678@234567151173.ingest.sentry.io/1234567'
    }
  ]
})

try {
  throw new Error('example')
} catch(error) {
  logger.error(error, { whatever: "is sent as extra" });
}

Configuration

level

default: info

Log only messages with a level less than or equal to this level. This acts as a global filter for all loggers unless a logger specifies its own level.

Available levels (in order of priority):

• trace (lowest)
• debug
• info
• warn
• error
• fatal (highest)

More info: https://www.npmjs.com/package/winston#logging-levels

service

default: user-service

The service name is used to identify the source of logs. This is particularly useful when aggregating logs from multiple services.

Loggers

Set of logging targets (transports) for log messages. Each logger can have its own configuration and log level.

Default configuration:

[
  {
    type: 'console'
  }
]

Available logger types:

• console - Logs to stdout/stderr
• errorFile - Logs errors to a file
• combinedFile - Logs all messages to a file
• sentry - Sends errors to Sentry for tracking

Note: The default loggers are replaced (not merged) when you provide a loggers array.

All loggers are implemented as Winston transports. More info: https://www.npmjs.com/package/winston#transports

sentry

• location (sentry.dsn)
• environment (default: production, sentry.environment)
• serverName (default: localhost, sentry.serverName)
• release (default: unknown, sentry.release)
• debug (default: false, sentry.debug)
• sampleRate (default: 1, sentry.sampleRate)
• tracesSampleRate (default: 1, sentry.tracesSampleRate)
• level (default: info)

DSN

The DSN tells the SDK where to send the events. If this value is not provided, the SDK will try to read it from the SENTRY_DSN environment variable. If that variable also does not exist, the SDK will just not send any events.

Example

const logger = makeLogger({
  loggers: [
    {
      type: 'sentry',
      location: 'https://12345678@234567151173.ingest.sentry.io/1234567',
      environment: 'production',
      release: 'v1.0.0',
      level: 'error'
    }
  ]
})

More info:

• https://github.com/aandrewww/winston-transport-sentry-node
• https://docs.sentry.io/platforms/node/
• https://docs.sentry.io/platforms/javascript/

errorFile

• location (default: error.log)
• level (default: error)

Logs error-level messages to a file.

Example

const logger = makeLogger({
  loggers: [
    {
      type: 'errorFile',
      location: './logs/error.log',
      level: 'error'
    }
  ]
})

combinedFile

• location (default: combined.log)

Logs all messages to a file regardless of level.

Example

const logger = makeLogger({
  loggers: [
    {
      type: 'combinedFile',
      location: './logs/combined.log'
    }
  ]
})

console

• level (default: trace)
• debug (default: false, includes stacktrace in output)
• format (default: simple, also accepts 'json' for structured logging systems)
• maxDepth (default: 5, maximum depth for nested objects in JSON format only)
• maxStringLength (default: 1000, maximum length for strings before truncation in JSON format only)

JSON Format Features

When using format: 'json', the console logger includes safe JSON serialization that handles:

• Circular references: Replaced with [Circular] to prevent serialization errors
• Deep objects: Objects exceeding maxDepth are replaced with [Max Depth Exceeded]
• Long strings: Strings exceeding maxStringLength are truncated with ... [truncated]
• Functions: Replaced with [Function] since they cannot be serialized
• Errors: Automatically captures message, stack, and metadata
• Stackdriver format: Compatible with Google Cloud Logging (includes severity, time, pid, hostname)

Examples

Simple console logging:

const logger = makeLogger({
  loggers: [{ type: 'console' }]
})

JSON format with custom depth limits:

const logger = makeLogger({
  loggers: [
    {
      type: 'console',
      format: 'json',
      maxDepth: 3,
      maxStringLength: 500,
      debug: true
    }
  ]
})

Combining Multiple Loggers

You can use multiple loggers simultaneously with different configurations:

const logger = makeLogger({
  level: 'debug',
  service: 'my-api',
  loggers: [
    {
      type: 'console',
      format: 'json',
      level: 'debug'
    },
    {
      type: 'errorFile',
      location: './logs/error.log',
      level: 'error'
    },
    {
      type: 'combinedFile',
      location: './logs/combined.log'
    },
    {
      type: 'sentry',
      location: process.env.SENTRY_DSN,
      environment: process.env.NODE_ENV,
      level: 'error'
    }
  ]
})

This configuration will:

• Log all debug+ messages to console in JSON format
• Log only errors to error.log
• Log all messages to combined.log
• Send only errors to Sentry