Custom Logger

Introduction

Xeno.JS lets you add your own logging provider by implementing ILoggerClient.

Create a Custom Logger

Implement ILoggerClient and its track() method:

import type { ILoggerClient, LogLevel } from '@xeno-js/shared'

class MyLogger implements ILoggerClient {
  track<T>(
    level: LogLevel,
    message: string,
    context: T,
    error?: unknown,
  ): void {
    console.log({
      level,
      message,
      context,
      error,
    })
  }
}

The track() method receives the log level, message, logging context, and optional error.

Register the Logger

Pass a factory through customLoggers:

import { AppBuilder } from '@xeno-js/core'

const app = new AppBuilder()

app.addLogger((options) => {
  options.customLoggers = [
    () => new MyLogger(),
  ]
})

The factory receives the current service scope:

options.customLoggers = [
  (container) => new MyLogger(),
]

Use the container only when the custom logger needs to resolve application services.

Resolve and Use the Logger

After building the application, resolve TOKENS.LOGGER:

import { AppBuilder, TOKENS } from '@xeno-js/core'

const app = new AppBuilder()

app.addLogger((options) => {
  options.customLoggers = [
    () => new MyLogger(),
  ]
})

await app.build()

const logger = app.resolve(TOKENS.LOGGER)

logger.info('Application started')
logger.error('Something went wrong', new Error('Example error'))

TOKENS.LOGGER resolves the Xeno.JS application logger. Your custom logger is registered as one of its logging clients, so it receives the log events together with any other configured providers.

Complete Example

import { AppBuilder, TOKENS } from '@xeno-js/core'
import type { ILoggerClient, LogLevel } from '@xeno-js/shared'

class MyLogger implements ILoggerClient {
  track<T>(
    level: LogLevel,
    message: string,
    context: T,
    error?: unknown,
  ): void {
    console.log({
      level,
      message,
      context,
      error,
    })
  }
}

const app = new AppBuilder()

app.addLogger((options) => {
  options.customLoggers = [
    () => new MyLogger(),
  ]
})

await app.build()

const logger = app.resolve(TOKENS.LOGGER)

logger.info('Hello from Xeno.JS')

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