Node JS: How to access MySQL remotely using SSH.

Recently I was working on a Data Migration Project. For one of the cases, I had to connect to a MySql database through an SSH Tunnel.

Here, I will show you how to get it done quickly.

We will be using ssh2 and mysql2 npm packages. So, make sure to install these.

Let’s get started by writing our database config file.

// dbConfig.js
// define connection config for the database
const dbServer = {
    host: process.env.DB_HOST,
    port: process.env.DB_PORT,
    user: process.env.DB_USERNAME,
    password: process.env.DB_PASSWORD,
    database: process.env.DB_DATABASE
}
// define connection config for the ssh tunnel
const tunnelConfig = {
    host: process.env.DB_SSH_HOST,
    port: 22,
    username: process.env.DB_SSH_USER,
    password: process.env.DB_SSH_PASSWORD
}

If you have to connect to SSH using a permission file, use privateKey as the key in place of password in the tunnelConfig object.

Example:

const tunnelConfig = {
    host: process.env.DB_SSH_HOST,
    port: 22,
    username: process.env.DB_SSH_USER,
    privateKey:
    require('fs').readFileSync('<path to your permission file>')
}

Now, we will specify the forward configuration for SSH.

// dbConfig.js
...
const forwardConfig = {
    srcHost: '127.0.0.1', // any valid address
    srcPort: 3306, // any valid port
    dstHost: dbServer.host, // destination database
    dstPort: dbServer.port // destination port
};

We are good to set up an SSH connection now.

// dbConfig.js
const mysql = require('mysql2');
const { Client } = require('ssh2');
// create an instance of SSH Client
const sshClient = new Client();
...
const SSHConnection = new Promise((resolve, reject) => {
    sshClient.on('ready', () => {
        sshClient.forwardOut(
        forwardConfig.srcHost,
        forwardConfig.srcPort,
        forwardConfig.dstHost,
        forwardConfig.dstPort,
        (err, stream) => {
             if (err) reject(err);
           
            // create a new DB server object including stream
            const updatedDbServer = {
                 ...dbServer,
                 stream
            };
            // connect to mysql
            const connection =  mysql.createConnection(updatedDbServer);
            // check for successful connection
           //  resolve or reject the Promise accordingly          
           connection.connect((error) => {
            if (error) {
                reject(error);
            }
            resolve(connection);
            });
       });
    }).connect(tunnelConfig);
});

Final Database Config File:

const mysql = require('mysql2');
const { Client } = require('ssh2');
const sshClient = new Client();
const dbServer = {
    host: process.env.DB_HOST,
    port: process.env.DB_PORT,
    user: process.env.DB_USERNAME,
    password: process.env.DB_PASSWORD,
    database: process.env.DB_DATABASE
}
const tunnelConfig = {
    host: process.env.DB_SSH_HOST,
    port: 22,
    username: process.env.DB_SSH_USER,
    password: process.env.DB_SSH_PASSWORD
}
const forwardConfig = {
    srcHost: '127.0.0.1',
    srcPort: 3306,
    dstHost: dbServer.host,
    dstPort: dbServer.port
};
const SSHConnection = new Promise((resolve, reject) => {
    sshClient.on('ready', () => {
        sshClient.forwardOut(
        forwardConfig.srcHost,
        forwardConfig.srcPort,
        forwardConfig.dstHost,
        forwardConfig.dstPort,
        (err, stream) => {
             if (err) reject(err);
             const updatedDbServer = {
                 ...dbServer,
                 stream
            };
            const connection =  mysql.createConnection(updatedDbServer);
           connection.connect((error) => {
            if (error) {
                reject(error);
            }
            resolve(connection);
            });
        });
    }).connect(tunnelConfig);
});

Now,SSHConnection Promise can be used wherever required.