Build a Node.js application that uses YSQL

The following tutorial shows a small Node.js application that connects to a YugabyteDB cluster using the node-postgres module and performs basic SQL operations. Use the application as a template to get started with YugabyteDB Aeon in Node.js.

Prerequisites

The latest version of Node.js.

Clone the application from GitHub

Clone the sample application to your computer:

git clone https://github.com/YugabyteDB-Samples/yugabyte-simple-node-app.git && cd yugabyte-simple-node-app

Provide connection parameters

If your cluster is running on YugabyteDB Aeon, you need to modify the connection parameters so that the application can establish a connection to the YugabyteDB cluster. (You can skip this step if your cluster is running locally and listening on 127.0.0.1:5433.)

To do this:

1. Open the sample-app.js file.

2. Set the following configuration parameter constants:

   • host - the host name of your YugabyteDB cluster. For local clusters, use the default (127.0.0.1). For YugabyteDB Aeon, select your cluster on the Clusters page, and click Settings. The host is displayed under Connection Parameters.
   • port - the port number for the driver to use (the default YugabyteDB YSQL port is 5433).
   • database - the name of the database you are connecting to (the default is yugabyte).
   • user and password - the username and password for the YugabyteDB database. For local clusters, use the defaults (yugabyte and yugabyte). For YugabyteDB Aeon, use the credentials in the credentials file you downloaded.
   • ssl - YugabyteDB Aeon requires SSL connections. To enable verify-ca SSL mode, the rejectUnauthorized property is set to true to require root certificate chain validation; replace path_to_your_root_certificate with the full path to the YugabyteDB Aeon cluster CA certificate.

3. Save the file.

Build and run the application

Install the node-postgres module.

npm install pg

Install the async utility:

npm install --save async

Start the application.

$ node sample-app.js

You should see output similar to the following:

>>>> Successfully connected to YugabyteDB!
>>>> Successfully created table DemoAccount.
>>>> Selecting accounts:
name = Jessica, age = 28, country = USA, balance = 10000
name = John, age = 28, country = Canada, balance = 9000
>>>> Transferred 800 between accounts.
>>>> Selecting accounts:
name = Jessica, age = 28, country = USA, balance = 9200
name = John, age = 28, country = Canada, balance = 9800

You have successfully executed a basic Node.js application that works with YugabyteDB Aeon.

Explore the application logic

Open the sample-app.js file in the yugabyte-simple-node-app folder to review the methods.

connect

The connect method establishes a connection with your cluster via the node-postgres driver.

try {
    client = new pg.Client(config);

    await client.connect();

    console.log('>>>> Connected to YugabyteDB!');

    callbackHadler();
} catch (err) {
    callbackHadler(err);
}

createDatabase

The createDatabase method uses PostgreSQL-compliant DDL commands to create a sample database.

try {
    var stmt = 'DROP TABLE IF EXISTS DemoAccount';

    await client.query(stmt);

    stmt = `CREATE TABLE DemoAccount (
        id int PRIMARY KEY,
        name varchar,
        age int,
        country varchar,
        balance int)`;

    await client.query(stmt);

    stmt = `INSERT INTO DemoAccount VALUES
        (1, 'Jessica', 28, 'USA', 10000),
        (2, 'John', 28, 'Canada', 9000)`;

    await client.query(stmt);

    console.log('>>>> Successfully created table DemoAccount.');

    callbackHadler();
} catch (err) {
    callbackHadler(err);
}

selectAccounts

The selectAccounts method queries your distributed data using the SQL SELECT statement.

try {
    const res = await client.query('SELECT name, age, country, balance FROM DemoAccount');
    var row;

    for (i = 0; i < res.rows.length; i++) {
        row = res.rows[i];

        console.log('name = %s, age = %d, country = %s, balance = %d',
            row.name, row.age, row.country, row.balance);
    }

    callbackHadler();
} catch (err) {
    callbackHadler(err);
}

transferMoneyBetweenAccounts

The transferMoneyBetweenAccounts method updates your data consistently with distributed transactions.

try {
    await client.query('BEGIN TRANSACTION');

    await client.query('UPDATE DemoAccount SET balance = balance - ' + amount + ' WHERE name = \'Jessica\'');
    await client.query('UPDATE DemoAccount SET balance = balance + ' + amount + ' WHERE name = \'John\'');
    await client.query('COMMIT');

    console.log('>>>> Transferred %d between accounts.', amount);

    callbackHadler();
} catch (err) {
    callbackHadler(err);
}

Learn more

node-postgres module