LogLayer

Basic Logging ​

LogLayer provides a simple and consistent API for logging messages at different severity levels. This guide covers the basics of logging messages.

Log Levels ​

LogLayer supports six standard log levels, each with its own method:

  • info() - For general information messages
  • warn() - For warning messages
  • error() - For error messages
  • debug() - For debug information
  • trace() - For detailed debugging information
  • fatal() - For critical errors that require immediate attention

INFO

Some logging libraries may not support all levels. In such cases:

  • trace is mapped to debug
  • fatal is mapped to error

Basic Message Logging ​

The simplest way to log a message is to use one of the log level methods:

typescript
// Basic info message
log.info('User logged in successfully')

// Warning message
log.warn('API rate limit approaching')

// Error message
log.error('Failed to connect to database')

// Debug message
log.debug('Processing request payload')

// Trace message (detailed debugging)
log.trace('Entering authentication function')

// Fatal message (critical errors)
log.fatal('System out of memory')

Message Parameters ​

All log methods accept multiple parameters, which can be strings, numbers, null, or undefined:

typescript
// Multiple parameters
log.info('User', 123, 'logged in')

// With string formatting (if supported by the logging library)
log.info('User %s logged in from %s', 'john', 'localhost')

WARNING

  • Support for multiple parameters depends on your logging library. Some libraries may only use the first parameter.
  • It's generally not recommended to use multiple parameters for log messages. Especially if you are going to use multiple logging transports as some may not support it.

Message Prefixing ​

You can add a prefix to all log messages either through configuration or using the withPrefix method:

typescript
// Via configuration
const log = new LogLayer({
  prefix: '[MyApp]',
  transport: new ConsoleTransport({
    logger: console
  })
})

// Via method
const prefixedLogger = log.withPrefix('[MyApp]')

// Output: "[MyApp] User logged in"
prefixedLogger.info('User logged in')

Enabling/Disabling Logging ​

You can control whether logs are output using these methods:

typescript
// Disable all logging
log.disableLogging()

// Enable logging again
log.enableLogging()

You can also configure this through the initial configuration:

typescript
const log = new LogLayer({
  enabled: false, // Starts with logging disabled
  transport: new ConsoleTransport({
    logger: console
  })
})

Transport Instance ​

You can get the underlying logger for a transport if you've assigned an ID to it:

typescript
const log = new LogLayer({
  transport: new ConsoleTransport({
    logger: console,
    id: 'console'
  })
})

const consoleLogger = log.getLoggerInstance<typeof console>('console')
typescript
import { type P, pino } from "pino";
import { PinoTransport } from "@loglayer/transport-pino";

const log = new LogLayer({
  transport: new PinoTransport({
    logger: pino(),
    id: 'pino'
  })
})

const pinoLogger = log.getLoggerInstance<P.Pino>('pino')