AWS Lambda functions NodeJs for postgreSQL - timeout error

user_6674171 0
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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?

aws-lambda amazon-rds node.js postgresql
2 Answers

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 !

user_64831210

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)
  }
};
user_11687860
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