Node.js

Learn how to connect to PostgreSQL databases in Sealos DevBox using Node.js

This guide will walk you through the process of connecting to a PostgreSQL database using Node.js within your Sealos DevBox project.

Prerequisites

Install Required Packages

In your Cursor terminal, install the necessary packages:

npm install pg dotenv

This command installs:

  • pg: The PostgreSQL client for Node.js
  • dotenv: A zero-dependency module that loads environment variables from a .env file

Connection Setup

Set up the environment and create a client

First, we'll import the required modules and set up the database configuration:

const { Client } = require('pg');
require('dotenv').config();
 
const dbConfig = {
  user: process.env.DB_USER,
  password: process.env.DB_PASSWORD,
  host: process.env.DB_HOST,
  port: process.env.DB_PORT,
  database: process.env.DB_NAME,
};
 
const client = new Client(dbConfig);

Create connection and query functions

Next, we'll create functions to handle database connection and query execution:

async function connectToDatabase() {
  try {
    await client.connect();
    console.log('Connected to PostgreSQL database');
  } catch (err) {
    console.error('Error connecting to PostgreSQL database', err);
    throw err;
  }
}
 
async function executeQuery(query, values = []) {
  try {
    const result = await client.query(query, values);
    return result.rows;
  } catch (err) {
    console.error('Error executing query', err);
    throw err;
  }
}
 
async function closeDatabaseConnection() {
  try {
    await client.end();
    console.log('Connection to PostgreSQL closed');
  } catch (err) {
    console.error('Error closing connection', err);
  }
}

Implement database operations

Now, let's implement functions for various database operations:

async function createTable() {
  const createTableQuery = `
    CREATE TABLE IF NOT EXISTS employees (
      id SERIAL PRIMARY KEY,
      name VARCHAR(100) NOT NULL,
      position VARCHAR(100) NOT NULL
    );
  `;
  await executeQuery(createTableQuery);
  console.log('Table created successfully');
}
 
async function insertEmployee(name, position) {
  const insertQuery = 'INSERT INTO employees(name, position) VALUES ($1, $2) RETURNING *';
  const values = [name, position];
  const result = await executeQuery(insertQuery, values);
  console.log('Employee inserted:', result[0]);
}
 
async function updateEmployee(id, name, position) {
  const updateQuery = 'UPDATE employees SET name = $1, position = $2 WHERE id = $3 RETURNING *';
  const values = [name, position, id];
  const result = await executeQuery(updateQuery, values);
  console.log('Employee updated:', result[0]);
}
 
async function getAllEmployees() {
  const selectQuery = 'SELECT * FROM employees';
  const employees = await executeQuery(selectQuery);
  console.log('All employees:', employees);
}

Create a main function to run operations

Finally, let's create a main function to demonstrate all the operations:

async function main() {
  try {
    await connectToDatabase();
    await createTable();
    await insertEmployee('John Doe', 'Developer');
    await insertEmployee('Jane Smith', 'Designer');
    await updateEmployee(1, 'John Updated', 'Senior Developer');
    await getAllEmployees();
  } catch (err) {
    console.error('An error occurred:', err);
  } finally {
    await closeDatabaseConnection();
  }
}
 
main();

Here’s the complete code to connect to the Postgres database with Node.js:

test-connection.js
const { Client } = require('pg');
require('dotenv').config();
 
const dbConfig = {
  user: process.env.DB_USER,
  password: process.env.DB_PASSWORD,
  host: process.env.DB_HOST,
  port: process.env.DB_PORT,
  database: process.env.DB_NAME,
};
 
const client = new Client(dbConfig);
 
async function connectToDatabase() {
  try {
    await client.connect();
    console.log('Connected to PostgreSQL database');
  } catch (err) {
    console.error('Error connecting to PostgreSQL database', err);
    throw err;
  }
}
 
async function executeQuery(query, values = []) {
  try {
    const result = await client.query(query, values);
    return result.rows;
  } catch (err) {
    console.error('Error executing query', err);
    throw err;
  }
}
 
async function closeDatabaseConnection() {
  try {
    await client.end();
    console.log('Connection to PostgreSQL closed');
  } catch (err) {
    console.error('Error closing connection', err);
  }
}
async function createTable() {
  const createTableQuery = `
    CREATE TABLE IF NOT EXISTS employees (
      id SERIAL PRIMARY KEY,
      name VARCHAR(100) NOT NULL,
      position VARCHAR(100) NOT NULL
    );
  `;
  await executeQuery(createTableQuery);
  console.log('Table created successfully');
}
 
async function insertEmployee(name, position) {
  const insertQuery = 'INSERT INTO employees(name, position) VALUES ($1, $2) RETURNING *';
  const values = [name, position];
  const result = await executeQuery(insertQuery, values);
  console.log('Employee inserted:', result[0]);
}
 
async function updateEmployee(id, name, position) {
  const updateQuery = 'UPDATE employees SET name = $1, position = $2 WHERE id = $3 RETURNING *';
  const values = [name, position, id];
  const result = await executeQuery(updateQuery, values);
  console.log('Employee updated:', result[0]);
}
 
async function getAllEmployees() {
  const selectQuery = 'SELECT * FROM employees';
  const employees = await executeQuery(selectQuery);
  console.log('All employees:', employees);
}
 
async function main() {
  try {
    await connectToDatabase();
    await createTable();
    await insertEmployee('John Doe', 'Developer');
    await insertEmployee('Jane Smith', 'Designer');
    await updateEmployee(1, 'John Updated', 'Senior Developer');
    await getAllEmployees();
  } catch (err) {
    console.error('An error occurred:', err);
  } finally {
    await closeDatabaseConnection();
  }
}
 
main();

Usage

Before running the script, create a .env file in the same directory with the following content:

.env
DB_USER=your_username
DB_PASSWORD=your_password
DB_HOST=your_database_host
DB_PORT=5432
DB_NAME=your_database_name

Replace the placeholders with your actual PostgreSQL credentials from the Database app in Sealos.

To test the connection, run the test script:

node test-connection.js

This will execute all the operations defined in the main function, demonstrating the connection to the database, table creation, data insertion, updating, and querying.

Best Practices

  1. Use environment variables for database credentials.
  2. Always handle potential errors using try-catch blocks.
  3. Close the database connection after operations are complete.
  4. Use parameterized queries to prevent SQL injection.
  5. Consider using connection pooling for better performance in production environments.

Troubleshooting

If you encounter connection issues:

  1. Verify your database credentials in the .env file.
  2. Ensure your PostgreSQL database is running and accessible.
  3. Check for any network restrictions in your DevBox environment.
  4. Confirm that the pg package is correctly installed.

For more detailed information on using PostgreSQL with Node.js, refer to the node-postgres documentation.

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