tracing-logger

The tracing-logger is an opinionated implementation of the winston logger that simplifies tracing and correlation of log messages within a single application, and across services.

When used across multiple services, you can also enjoy a consistent log format making it more straightforward to create search facets in your log tooling.

The log level is set to info where NODE_ENV is production, and debug otherwise.

Log Format

Each log message is created with a UTC timestamp and a tracing node. This will contain an x-correlation-id uuid at a minimum in addition to any other values you choose to add.

{
  "timestamp":"2020-06-22T21:13:36.105Z",
  "tracing":{
    "x-correlation-id":"a71cabcc-7f89-451b-b72c-baeee9f3c7c5",
    "user-id":"38e2c385-bd20-4e98-91b7-930d22959989"
  },
  "message":"some log message or data",
  "level":"debug"
}

The logger should be initialised and added as middleware to your server to allow it to intercept each incoming request.

The x-correlation-id attribute is added automatically when the logger is initialised.
If this header is provided then the consumer provided value will be used, otherwise a new uuid will be generated and added.

Additional values can be appended to the tracing object for automatic inclusion on all log messages.

Initialisation

const express = require('express')

// Import the tracing-logger package
const logger = require('tracing-logger')

const app = express()
const port = 3000

// Initialise the logger, this will create a tracing namespace that
// is unique to the current request.  If that request contains an
// `x-correlation-id` header the value will be added to the tracing
// object on the logger, otherwise a new uuid will be generated and used.
app.use(logger.init());

app.get('/', (req, res) => {
  logger.info("x-correlation-id attached")

  // Further tracing values can be added as required
  logger.tracing.set('service name', 'express example')
  logger.info("service name attached")

  // All tracing values can be accessed at once,
  // this is useful when passing values to
  // downstream services
  res.send(logger.tracing.getAll())
})

app.listen(port, () => logger.info(`Example app listening at http://localhost:${port}`))

Usage

// The logger can be imported in any file within
// the service, it will still have access to the
// same tracing values which will be automatically
// included on any logs
const logger = require('tracing-logger')

const books = [
  {
    title: 'Wuthering Heights',
    author: 'Emily Brontë',
  },
  {
    title: 'Jurassic Park',
    author: 'Michael Crichton',
  },
];

const fetchAll = () => {
  logger.debug(`Fetching All Of The Data: ${JSON.stringify(books)}`);
  return books;
};

const callDownstream = () => {
  const xCorrelationId = logger.tracing.get('x-correlation-id');

  // attach the xCorrelationId to the
  // `x-correlation-id` request header
  // when making downstream requests
};

module.exports = { fetchAll };

See the apollo-server-express example for a working demonstration.