Lambda#

lambda-function-url

Lambda handler response stream

import util from 'util'
import stream from 'stream'
const { Readable } = stream
const pipeline = util.promisify(stream.pipeline)


export const handler = awslambda.streamifyResponse(
  async (event, responseStream, _context) => {
    const requestStream = Readable.from(
      Buffer.from(new Array(1024 * 1024).join('🚣'))
    )
    await pipeline(requestStream, responseStream)
  }
)

Introduction#

First init a new project

npm init

Install AWS SDK version 3

npm install @aws-sdk/client-s3

Setup type module in the package.json

{
  "name": "aws-sdk-nodejs-demo",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "type": "module",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "@aws-sdk/client-s3": "^3.344.0"
  }
}

Invoke Lambda#

Install client-lambda in case we want to invoke lambda function by nodejs

npm install @aws-sdk/client-SERVICE

here

and invoke the lambda function by nodejs

import { InvokeCommand, LambdaClient, LogType } from '@aws-sdk/client-lambda'


const client = new LambdaClient({ region: 'us-east-1' })


const commnad = new InvokeCommand({
  FunctionName: 'HelloStream',
  Payload: JSON.stringify({
    name: 'haimtran',
    content: 'Lambda is a compute service that lets you run code without'
  }),
  LogType: LogType.Tail
})


const { Payload, LogResult } = await client.send(commnad)


console.log(Payload)


// const result = Buffer.from(Payload).toString();


// console.log(result)

Lambda Response Stream#

First we can display the receiving stream by curl

curl --request GET https://uuiuhow5ttlcc4enlmo6caqtdq0wfwjw.lambda-url.us-east-1.on.aws/

Second receive by Javascript at client web browser. This is chunk by chunk of byte and decode it to text as the following

'use client'


import { useState } from 'react'
import { StreamingTextResponse } from 'ai'


export default function Home() {
  const [messages, setMessages] = useState<String[]>([])


  const callLambda = async () => {
    const response = await fetch(
      'https://uuiuhow5ttlcc4enlmo6caqtdq0wfwjw.lambda-url.us-east-1.on.aws/',
      {
        method: 'GET'
      }
    )
    const reader = response.body?.getReader()
    const read = () => {
      reader?.read().then(({ done, value }) => {
        if (done) {
          console.log('done')
          return
        }
        const decoder = new TextDecoder()
        console.log(decoder.decode(value))
        setMessages([...messages, decoder.decode(value)])
        read()
      })
    }


    read()
  }


  return (
    <main className="">
      <div className="mx-auto max-w-4xl flex flex-col gap-5">
        <button
          className="rounded-sm px-10 py-3 bg-green-600 text-white"
          onClick={() => {
            console.log('call lambda stream')
            callLambda()
          }}
        >
          Call Lambda
        </button>
        <div className="w-full break-words bg-slate-200 h-96 overflow-y-auto">
          {messages.map((message, id) => (
            <div key={id}>{message}</div>
          ))}
        </div>
      </div>
    </main>
  )
}

[!IMPORTANT] Please enable CORL and RESPONSE_STREAM MODE in lambda function url

lambda-function-url

Reference#