https://rcoedo.com/blog/2020/05/25/async-local-storage-for-easy-context-passing-in-node-js

async-local-storage-create-namespace.js

const { AsyncLocalStorage } = require("async_hooks");

const asyncLocalStorage = new AsyncLocalStorage();

async-local-storage-express-middleware.js

const requestIdMiddleware = (req, res, next) => {
  asyncLocalStorage.run(new Map(), () => {
    asyncLocalStorage.getStore().set("requestId", uuid());
    next();
  });
};

async-local-storage-express-server.js

const express = require("express");
const { AsyncLocalStorage } = require("async_hooks");
const uuid = require("uuid/v4");

const asyncLocalStorage = new AsyncLocalStorage();

const requestIdMiddleware = (req, res, next) => {
  asyncLocalStorage.run(new Map(), () => {
    asyncLocalStorage.getStore().set("requestId", uuid());
    next();
  });
};

const app = express();

app.use(requestIdMiddleware);

app.get("/", (req, res) => {
  const id = asyncLocalStorage.getStore().get("requestId");
  console.log(`[${id}] request received`);
  res.send("It works!");
});

const port = process.env.PORT || 3000;
app.listen(port, () => console.log(`Express server listening on port ${port}`));

Examples for "AsyncLocalStorage for Easy Context Passing in Node.js"

This gist contains the examples for the article "AsyncLocalStorage for Easy Context Passing in Node.js".

- https://medium.com/trabe/asynclocalstorage-for-easy-context-passing-in-node-js-e33c84679516
- https://rcoedo.com/blog/2020/05/25/async-local-storage-for-easy-context-passing-in-node-js