NodeJS Express - Global Unique Request Id

Question

Is it possible to define a unique request Id that is included in each log statement without handing the logger to each method/function call?

Technologies in use: NodeJS, Express, Winston

Answer 1

Edited

Finally, I have created a library that makes all the work. https://github.com/davicente/express-logger-unique-req-id

It is a wrapper of Winston library, so you can use it the same way.

Let me know if it helps you

---

We had this same problem in several projects, and I couldn't finde any complete solution for this question. We are using same technologies (Node.js, Express.js and Winston for logs) I found a solution to this using a couple of libraries and wrapping Winston library: - node-uuid for creating unique identificators for each request - continuation-local-storage for sharing this IDs among different modules without sending req object in all the calls.

First I need to create and set the unique identificator with each request. I do it in the middleware:

var uuid = require('node-uuid');
var createNamespace = require('continuation-local-storage').createNamespace;
var myRequest = createNamespace('my request');

// Run the context for each request. Assign a unique identifier to each request
app.use(function(req, res, next) {
    myRequest.run(function() {
        myRequest.set('reqId', uuid.v1());
        next();
    });
});

After that I had to wrap Winston library, recovering the id from the context and adding to the message of the log:

var winston = require('winston');
var getNamespace = require('continuation-local-storage').getNamespace;

// Wrap Winston logger to print reqId in each log
var formatMessage = function(message) {
    var myRequest = getNamespace('my request');
    message = myRequest && myRequest.get('reqId') ? message + " reqId: " + myRequest.get('reqId') : message;
    return message;
};

var logger = {
    log: function(level, message) {
        winstonLogger.log(level, formatMessage(message));
    },
    error: function(message) {
        winstonLogger.error(formatMessage(message));
    },
    warn: function(message) {
        winstonLogger.warn(formatMessage(message));
    },
    verbose: function(message) {
        winstonLogger.verbose(formatMessage(message));
    },
    info: function(message) {
        winstonLogger.info(formatMessage(message));
    },
    debug: function(message) {
        winstonLogger.debug(formatMessage(message));
    },
    silly: function(message) {
        winstonLogger.silly(formatMessage(message));
    }
};
module.exports = logger;

I think it was a little bit complex, so I decided to write it down in a post. You can get more information from there: Express.js: Logging info with global unique request ID – Node.js

I hope this helps with your problem.

Answer 2

This answer has a problem: the counter goes back to 0 every time the node process is restarted. Turns out there is fairly simple to work around. You simply add an express middleware that tags each request called with a UUID using the uuid package.

For uuid Pre-2.0

const uuid = require('uuid');
const app = express();
app.use(function (req, next) {
  req.id = uuid.v4();
  next();
});

For uuid 3.0+

const uuidv4 = require('uuid/v4');
const app = express();
app.use(function (req, next) {
  req.id = uuidv4();
  next();
});