Hapi.js 中的 AsyncLocalStorage

Question

I trying to add trace id in async storage, onRequest. But in the handler, there is no stored data. Why data is empty in handler? What am I do wrong?

async local storage:

const {AsyncLocalStorage} = require('async_hooks')
const asyncLocalStorage = new AsyncLocalStorage() 
module.exports = {
  asyncLocalStorage
}

setup:

server.ext({
    type: 'onRequest',
    method(request, h) {
      return new Promise(resolve => {
        getLocalStorage().run({meta: {traceId: 'id'}}, () => {
          return resolve(h.continue)
        })
      })
    },
  })

handler:

    {
    path: '/',
    method: 'GET',
    handler: (req) => {
      const data = asyncLocalStorage.getStore()
      //why data is undefined?
      return data;
    },
    options: {
      tags: ['api', 'Test'],
      description: "Test",
      auth: {
        strategy: 'jwt_user',
        scope: ['USER'],
      },
      response: {
        schema: testResponseSchema,
        modify: true,
        options: {
          stripUnknown: true,
          convert: true,
        },
      },
    },
  },

Answer 1

I was able to get it to work (note - I am still testing this) using a wrapper over the handler function like below.

Step 1: Create a file async-local-storage.js

// async-local-storage.js

const { AsyncLocalStorage } = require('async_hooks')

module.exports = {
  asyncLocalStorage: new AsyncLocalStorage(),
}

Step 2: Create a wrapper for handler function

// handle-request.js

const asyncLocalStorage = require('./async-local-storage').asyncLocalStorage

function handleRequest(handler) {
  return (req, h) => {
    const correlationId = req.headers['correlationId']
    return asyncLocalStorage.run({ correlationId : correlationId || 'Not set' }, async () => {
      return handler(req, h)
    })
  }
}

module.exports = {
  handleRequest,
}

Step 3: In each route, use the handleRequest wrapper.

// routes.js

const handleRequest = require('./handle-request').handleRequest
const myTestApiHandler = require('./myTestApiHandler').myTestApiHandler

module.exports = [
{
    method: 'GET',
    path: '/api/my-test-api',
    config: {
      handler: handleRequest(myTestApiHandler),
    },
  },
}]

Now, in myTestApiHandler we can get correlationId like below.

// myTestApiHandler

const asyncLocalStorage = require('./async-local-storage').asyncLocalStorage

function myTestApiHandler(req, h) {
  const store = asyncLocalStorage.getStore();
  const correlationId = store.correlationId;
  ..
  ..
  
}

module.exports = {
  myTestApiHandler
}

The correlationId should also be available to any functions getting invoked from the myTestApiHandler function like logger etc.

Please refer official doc for AsyncLocalStorage for more details