ETIMEDOUT while using mysql2 with Express on AWS Lambda

Question

I am using mysql2 package with the Express Framework, deployed over AWS Lamda. I have the provisioned concurrency set to 3 for Aws Lambda.

I am not directly connecting to MySQL. I have RDS Proxy in between.

I am getting the following error, randomly.

{
    "errorType": "Error",
    "errorMessage": "connect ETIMEDOUT",
    "code": "ETIMEDOUT",
    "errorno": "ETIMEDOUT",
    "syscall": "connect",
    "fatal": true,
    "stack": [
        "Error: connect ETIMEDOUT",
        "    at Connection._handleTimeoutError (/var/task/node_modules/mysql2/lib/connection.js:178:17)",
        "    at listOnTimeout (internal/timers.js:554:17)",
        "    at processTimers (internal/timers.js:497:7)"
    ]
}

Following is what my code looks like:

var AWS = require("aws-sdk");
const mysql = require('mysql2');

class DBConnection {

    constructor() {

        var signer = new AWS.RDS.Signer({
            region: 'us-east-1',
            hostname: process.env.DB_HOST,
            port: 3306,
            username: process.env.DB_USER
        });
        
        let connectionConfig = {
            host: process.env.DB_HOST,
            user: process.env.DB_USER,
            database: process.env.DB_NAME,
            ssl: 'Amazon RDS',
            authPlugins: { mysql_clear_password: () => () => signer.getAuthToken() }
        };
        
        this.db = mysql.createConnection(connectionConfig);

    }

    query = async (sql, values) => {

        return new Promise((resolve, reject) => {

            this.db.execute(sql, values, (error, result) => {

                if (error) {
                    reject(error);
                    return;
                }

                resolve(result);

            });

        });

    }
}

module.exports = new DBConnection().query;

const results = await query('SELECT COUNT(*) AS total_listens FROM analytics WHERE event_name="PLAYED"');

Any clue where the issue can be?

Answer 1

With AWS Lambda function it's better to use mysql.createPool instead of mysql.createconnection. I don't know what's the specific reason but using mysql.createconnection instead of mysql.createPool has caused problems for me as well. It's also necessary to release the connection when the query goes successful.