nx-logger

nx-logger is a logging utility that grows with the application

• TypeScript 2.9
• Jest unit testing and code coverage
• Type definitions for Node.js v6.x (LTS) and Jest

Installation

npm i @raynode/nx-logger

Migrations

As nxLogger namespace was removed, the access to the internals like interfaces or the log levels was changed. This will result in the following being invalid:

import { nxLogger, create } from '@raynode/nx-logger'

const log = create({ verbosity: nxLogger.DEBUG })

it will be like this now:

import { LogLevel, create } from '@raynode/nx-logger'

const log = create({ verbosity: LogLevel.DEBUG })

Further the nxLogger is not necessary any more to access the interfaces

// before
import { nxLogger } from '@raynode/nx-logger'
type myLog = nxLogger.Log

// after
import { Log } from '@raynode/nx-logger'
type myLog = Log
// or
import { Log as myLog } from '@raynode/nx-logger'

Usage

Basic usage would just render some console output

import { create } from '@raynode/nx-logger'

const log = create('my-project')

log('start-up')

Will run this line of console output

console.log('my-project - start-up')

As I love Debug from visionmedia, there is already a transport to transform your logging.

import { create, configure } from '@raynode/nx-logger'
import { transport } from '@raynode/nx-logger-debug'

configure({ transport })

const log = create('my-project')

log('start-up')

This will now send the log message through debug, including the namespaces

Features

• Namespaces
• Interchangeable transports
• Verbosity Settings
• Function-Call logging
• Joining and splitting of transports

Namespaces

Each logging instance can have its own namespace. They are designed to be inherited and used per file or per context.

You could configure it per file (with default transport)

// app.ts
configure({ namespace: ['project'] })
const context = create('app')
// Result: project - app : msg

// utils.ts
const context = create('utils')
// Result: project - utils : msg

Or you can use it as per request

configure({ namespace: ['project'] })
const appLog = create('express')
const app = express()
app.use((req, res, next) => {
  req.log = appLog(req.url)
  next()
})

app.get('/something/*', (req, res) => {
  req.log('making')
  // Result: project - express - /something/more : making
})

Transports

The nx-logger is written in a way that lets you start a project and have simple logging output. And after the project grows you'll only have to attach another transport to send the log output directly to your logging servers or services (like: Loggly).

Verbosity

Like in console there are some functions to define the verbosity of the logging call.

const context = create({
  verbosity: 5, // default
})

context.debug('DEBUG-level: 10')
context.info('INFO-level: 7')
context.log('LOG-level: 5')
context('LOG-level: 5')
context.warn('WARN-level: 3')
context.error('ERROR-level: 1')

The verbosity is set per namespace to more easily debug problems during development.

Functionhandlers

Sometime we need to know when a specific function is called, and we write code like this:

const myFunction = (a, b) => {
  context.log('myFunction', [a, b])
  // ...
}

myFunction(1, 2) // myFunction [1, 2]

nx-logger has a logging handler for this case:

const myFunction = context.on((a, b) => {
  // ...
}, 'myFunction')

myFunction(1, 2) // myFunction [1, 2]

The context.on(callback, [namespace], [configuration]) feature will enable you to get information whenever the defined function is called. Combined with the conditions feature it might look like this

const signup = context.on((user: User) => db.run('create', user), 'signup-user', {
  transport: join(transport, createTransport(logglyConfiguration)),
})

Conditions

When a project grows and it is necessary to enable new logging functions, it might be nice to have a possibility to join transports together.

import { create, join } from '@raynode/nx-logger'
import { transport } from '@raynode/nx-logger-debug'
import { createTransport } from '@raynode/nx-logger-loggly'

const context = create({
  transport: join(transport, createTransport(logglyConfiguration))
})

context.log('message') // will show up in the console through debug and be transmitted to loggly via loggly-transport.

It might also be good to decide which messages are used in some transport

import { create, split, LogLevel } from '@raynode/nx-logger'
import { transport } from '@raynode/nx-logger-debug'
import { createTransport } from '@raynode/nx-logger-loggly'

const decide = (configuration, messages, verbosity) => {
  if(verbosity > LogLevel.LOG)
    return true // use debug
  else
    return false // use loggly for LOG and below
}

const context = create({
  transport: split(decide, transport, createTransport(logglyConfiguration))
})

context.log('important') // will be transmitted to loggly via loggly-transport.
context.info('just infos') // will show up in the console through debug

Contributing

If you want to help with this project, just leave a bugreport or pull request. I'll try to come back to you as soon as possible

License

MIT