AsyncLocalStorage: Simplify Context Management in Node.js

AsyncLocalStorage gives you a way to maintain context across your async operations without manually passing data through every function. Think of it like having a secret storage box that follows your request around, carrying important information that any part of your code can access.

Here’s what a typical Express application without AsyncLocalStorage might look like. We need to pass the userId through multiple functions:

async function handleRequest(req, res) {
  const userId = req.headers['user-id'];

  await validateUser(userId);
  await processOrder(userId);
  await sendNotification(userId);
}

async function validateUser(userId) {
  // Need userId here
}

async function processOrder(userId) {
  // Need userId here too
  await updateInventory(userId);
}

async function updateInventory(userId) {
  // Still need userId here
}

async function sendNotification(userId) {
  // And here
}

Notice how we keep passing userId everywhere? Now multiply this by several more parameters like requestId, tenantId, and locale. The function signatures grow unwieldy fast.

Here’s how we can clean this up with AsyncLocalStorage

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