@squeep/logger-json-console

A simple logger class, which mostly just structures messages, data, and some metadata as JSON and spews it, by default, to Console.

Supports basic scrubbing of well-defined sensitive fields, detection of circular references, and an extensible set of JSON replacer functions for common objects.

If provided with an asyncLocalStorage instance, it expects a stored object which will be spread over the resulting logged JSON.

Intended to be specific to Squeep Framework Applications, this module has some opinions.

API

• new Logger(options, commonObject, asyncLocalStorage, backend)

  • commonObject will be merged into every log
  • asyncLocalStorage, if provided, should store an object, which will also be merged into log
  • backend is console by default, but may be anything implementing the same log-level functions

• error(scope, message, data, ...)

  • scope - identifies source of message, e.g. 'class:method'
  • message - text to be logged
  • data - object to be logged, can be scrubbed of sensitive fields, and will be serialized with provided replacers
  • any additional arguments are included as an array

• warn(scope, message, data, ...)

• info(scope, message, data, ...)

• log(scope, message, data, ...)

• debug(scope, message, data, ...)

JSON Replacers

Includes replacers for these objects:

• Error
• BigInt
• http.IncomingMessage
• http.OutgoingMessage
• http.ServerResponse

Additional replacers may be inserted into the logger instance's jsonReplacers array.

Data Sanitizers

Sanitizers may be inserted into the logger instance's dataSanitizers array.

Example

const http = require('node:http');
const { AsyncLocalStorage } = require('node:async_hooks');
const uuid = require('uuid');
const Logger = require('@squeep/logger-json-console');

const loggerOptions = {
  ignoreBelowLevel: 'info',
};
const commonObject = {
  nodeIdentifier: uuid.v1(),
};
const asyncLocalStorage = new AsyncLocalStorage();
const logger = new Logger(loggerOptions, commonObject, asyncLocalStorage);

const scope = 'exampleServer';
http.createServer((req, res) => {
  asyncLocalStorage.run({ requestId: uuid.v1() }, () => {
    logger.debug(scope, 'start', { req, res });
    setImmediate(() => {
      res.end();
      logger.info(scope, 'finish', { req, res }, 'other stuff');
    });
  });
}).listen(8088);

Results in messages such as this:

{
  "nodeIdentifier": "64610280-fc17-11ed-a918-1dd19f027d43",
  "timestamp": "2023-05-26T22:48:17.995Z",
  "timestampMs": 1685141297995,
  "level": "info",
  "scope": "exampleServer",
  "message": "finish",
  "data": {
    "req": {
      "method": "GET",
      "url": "/",
      "httpVersion": "1.1",
      "headers": {
        "host": "localhost:8088",
        "user-agent": "curl/7.83.1",
        "accept": "*/*"
      },
      "trailers": {}
    },
    "res": {
      "statusCode": 200,
      "statusMessage": "OK",
      "headers": {}
    }
  },
  "other": [
    "other stuff"
  ],
  "requestId": "68233aa0-fc17-11ed-a918-1dd19f027d43"
}