CODEWITHSUNDEEP
node.jsloggingwinston
Max Block
Max Block

Reputation: 1444

How to make a custom json formatter for winston@3 logger?

I'm trying to make a custom json formatter for winston v3.

Here is a single file with demo:

const { createLogger, format, transports } = require("winston")
const { combine, timestamp, prettyPrint } = format

const logger = createLogger({
  format: combine(timestamp(), prettyPrint())
})

logger.add(new transports.Console())

logger.info("test message", { data: { a: 1, b: [1, 2, 3, 4], d: new Date() } })

try {
  throw new Error("I'm an error!")
} catch (err) {
  logger.error(err)
}

It prints:

{ data: { a: 1, b: [ 1, 2, 3, 4 ], d: 2018-07-21T08:59:27.958Z },
  level: 'info',
  message: 'test message',
  timestamp: '2018-07-21T08:59:27.959Z',
  [Symbol(level)]: 'info',
  [Symbol(splat)]:
   [ { data: { a: 1, b: [ 1, 2, 3, 4 ], d: 2018-07-21T08:59:27.958Z } } ] }
{ Error: I'm an error!
    at Object.<anonymous> (/Users/max7z/projects/test/t32__test__winston__pretty-print_symbol/index.js:13:9)
    at Module._compile (internal/modules/cjs/loader.js:689:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:700:10)
    at Module.load (internal/modules/cjs/loader.js:599:32)
    at tryModuleLoad (internal/modules/cjs/loader.js:538:12)
    at Function.Module._load (internal/modules/cjs/loader.js:530:3)
    at Function.Module.runMain (internal/modules/cjs/loader.js:742:12)
    at startup (internal/bootstrap/node.js:266:19)
    at bootstrapNodeJSCore (internal/bootstrap/node.js:596:3)
  level: 'error',
  timestamp: '2018-07-21T08:59:27.962Z',
  [Symbol(level)]: 'error' }

I'd like to have almost the same output, but without some fields: [Symbol(level)], [Symbol(splat)].

Is it possible to remove [Symbol] fields from prettyPrint formatter?

Or how can I make my own custom json formatter with error stacktrace like prettyPrint has?

Upvotes: 5

Views: 23315

Answers (4)

Tan Nguyen
Tan Nguyen

Reputation: 1101

Refer Winston format

require('winston-daily-rotate-file');
const { createLogger, format, transports } = require('winston');
const { combine, timestamp, label, printf, prettyPrint, splat, simple } = format;
 

const myFormat = printf(info => {
    // you can get splat attribue here as info[Symbol.for("splat")]
    // if you custome splat please rem splat() into createLogger()
    return `${info.timestamp} [${info.label}] ${info.level}: ${info.message}`;
});

const logger = createLogger({
  format: combine(
    label({ label: 'dicom-interactive.com' }),
    timestamp(),
    splat(),
    myFormat
  ),
  transports: [
      new transports.Console(),
      new transports.File({
        filename: "info.log",
        level: 'info'
      }),
      new transports.File({
        filename: "error.log",
        level: 'error'
      })
    ]
})
 
logger.info("test message %o", { data: { a: 1, b: [1, 2, 3, 4], d: new Date() } });

module.exports = logger;

Upvotes: 2

Benny Code
Benny Code

Reputation: 54812

I tested the sample with winston v3.3.3 and added a custom formatter to stringify the data object:

const winston = require('winston');

const myFormatter = winston.format((info) => {
  const {message} = info;

  if (info.data) {
    info.message = `${message} ${JSON.stringify(info.data)}`;
    delete info.data; // We added `data` to the message so we can delete it
  }
  
  return info;
})();

const logger = winston.createLogger({
  format: winston.format.combine(
    winston.format.timestamp({
      format: 'YYYY-MM-DD HH:mm:ss',
    }),
    myFormatter,
    winston.format.simple(),
  ),
  transports: [
    new winston.transports.Console(),
  ],
});

I ran the commands from the question and got the desired output.

Execution:

logger.info('test message', {data: {a: 1, b: [1, 2, 3, 4], d: new Date()}});

try {
  throw new Error(`I'm an error!`);
} catch (err) {
  logger.error(err);
}

Output:

info: test message {"a":1,"b":[1,2,3,4],"d":"2020-09-09T09:41:22.525Z"} {"timestamp":"2020-09-09 11:41:22"}

error: I'm an error! {"timestamp":"2020-09-09 11:41:22"}

The JSON object can be also printed with tabs and line breaks when using winston.format.prettyPrint() instead of winston.format.simple().

Upvotes: 6

PhiloSophia
PhiloSophia

Reputation: 21

I've encountered kind of same problem and found solution in here. I am using Node.js and Socket.IO,I've used logger in Socket.IO. As an example:

Node.js

io.on('connection',function(socket){
  var date = new Date();
  socket.on('',function(data){
    logger.log('info', {IP: ip, Date: date, Path: '', Data: data.req_data});

Winston.js(logger)

const app_root = require('app-root-path');
const { createLogger, format, transports } = require('winston');


var logger = createLogger({
  level: 'info',
  format: format.combine(
    format(function(info, opts){
        console.log(`[${info.IP}]-[${info.Date}]-[${info.Path}]-[${info.Data}]`);
        return info;
    })(),
    format.json()

  ),

  transports: [
    new transports.File({filename: `${app_root}/logs/info.log`})
  ]
});

module.exports = logger;

As much as I understand we can use random variables(ip,date,bird,ball, etc..) as we want. I think after little bit arrangment you can use this for errors too. Good luck!

Upvotes: 2

Lucas S.
Lucas S.

Reputation: 2401

Check out how to create custom formats. Then use the source code of prettyPrint as a base to create a modified version based on your needs.

Winstons uses triple-beam for definitions for the various Symbols, so you can also use that package to remove them.

Upvotes: 5

Related Questions