在等待数据库查询之前返回 AWS Lambda 响应 - 无服务器框架

Question

I have a serverless framework node.js function that initializes mysql DB and then runs a query, ES6 is used to return an HTTP response at the end

1. Is there a way to return the response before waiting for the DB call to finish, for example in node.js - res.send will return immediately and the function continues to run after the response is returned

2. Is there a better way to initialize a new mysql pool (perhaps reuse the pool instead of creating an ending it in each request?)

   a: If for example the answer is to create the pool outside the function, how does it exactly work and how does the lambda function reuse it between requests, when does it get destroyed and how does it know when to recreate the pool

import mysql from "mysql";

export const myFunc = async (event) => {
  try {
    const pool = mysql.createPool({...}); // Creates a new mysql pool

    await new Promise((resolve, reject) => {pool.query(
      "INSERT STATEMENT", [...params], (error, results) => {
      if(error) reject(error)
      resolve(results)
}
    )});

    pool.end();

    return {
      statusCode: 200,
      body: JSON.stringify({message: 'End'}),
    };
  } catch (err) {
    return {
      statusCode: 500,
      body: JSON.stringify({message: 'Error'}),
    };
  }
};

Answer 1

1. Is there a way to return the response before waiting for the DB call to finish

Yes, but then the Lambda will finish executing before waiting for DB call finishing. It will not guarantee that the call to DB will reach the DB, so it's not recommended to do so .

If you absolutely need this, drop the await statement in this line:

From:

await new Promise((resolve, reject) => {pool.query(

To:

new Promise((resolve, reject) => {pool.query(

2. Is there a better way to initialize a new mysql pool (perhaps reuse the pool instead of creating an ending it in each request?)

Yes, you need to initialize your pool outside of Lambda handler.

Check out this article for more details:

https://dashbird.io/blog/leveraging-lambda-cache-for-serverless-cost-efficiency/

Basically, you want to do instead of:

import mysql from "mysql";

export const myFunc = async (event) => {
  try {
    const pool = mysql.createPool({...}); // Creates a new mysql pool

Do this:

import mysql from "MySQL";

const pool = mysql.createPool({...}); // Creates a new mysql pool

export const myFunc = async (event) => {
  try {