AWS Lambda functions NodeJs for postgreSQL - timeout error - node.js

Question

I am new to AWS. I am trying to connect to AWS RDS postgreSQL instance using Lambda functions. I followed the aws documentation. But it uses python for Lambda functions. Below is my code.
'use strict';
var pg = require('pg');
exports.handler = function (event, context) {
var dbConfig = {
username: '<username>',
password: '<password>',
database: '<database>',
host: '<db-endpoint>',
};
var client = new pg.Client(dbConfig);
try {
client.connect();
context.callbackWaitsForEmptyEventLoop = false;
client.end();
}
catch (err) {
console.log(err);
client.end();
}
};
I am getting timeout error as below
START RequestId: 368e619e-ed9d-4241-93a5-764ee01aa847 Version: $LATEST
2020-06-15T16:28:18.911Z 368e619e-ed9d-4241-93a5-764ee01aa847 INFO connected
END RequestId: 368e619e-ed9d-4241-93a5-764ee01aa847
REPORT RequestId: 368e619e-ed9d-4241-93a5-764ee01aa847 Duration: 20020.16 ms Billed Duration: 20000 ms Memory Size: 128 MB Max Memory Used: 70 MB Init Duration: 150.01 ms
2020-06-15T16:28:38.901Z 368e619e-ed9d-4241-93a5-764ee01aa847 Task timed out after 20.02 seconds
Please advise on the error.
I have few other questions to ensure if my code is correct
I gave db instance endpoint url for db-endpoint. is that right? or if not what should i use there?
is there any proper documentation available, for the beginners like me, about Lambda functions with nodejs to connect postgres on RDS?

Answer 1

You're not returning anything from the lambda. So the request keeps hanging without a response until it times out.
Use the third argument callback supplied to the handler to respond or return a Promise.
'use strict';
var pg = require('pg');
exports.handler = function (event, context,callback) {
var dbConfig = {
username: '<username>',
password: '<password>',
database: '<database>',
host: '<db-endpoint>',
};
var client = new pg.Client(dbConfig);
try {
client.connect();
context.callbackWaitsForEmptyEventLoop = false;
client.end();
//send the response
callback(null,"Some Response")
}
catch (err) {
console.log(err);
client.end();
callback(err)
}
};
AWS example : AWS Lambda NodeJS Connect to RDS Postgres Database
You can read the official js docs with all methods and properties here : https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/RDS.html
Hope this helps !

Answer 2

Here is the answer for async/await syntax
const { Client } = require("pg");
exports.handler = async (event, context, callback) => {
const dbConfig = {
host: process.env.RDS_HOSTNAME,
user: process.env.RDS_USERNAME,
password: process.env.RDS_PASSWORD,
port: process.env.RDS_PORT,
database: process.env.RDS_DATABASE,
};
const client = new Client(dbConfig);
try {
await client.connect();
const res = await client.query("SELECT * FROM your_table");
await client.end();
callback(null, res.rows);
} catch (err) {
await client.end();
callback(err)
}
};