How to create connection pool with TypeOrm

Creating a connection pool in TypeORM is relatively straightforward because TypeORM automatically manages the connection pool. When you establish a database connection, TypeORM configures and manages these connections for you. The following are the steps to create and configure the connection pool:

Step 1: Install TypeORM and Database Drivers

First, you need to install TypeORM and the corresponding database driver. For example, if you are using PostgreSQL, you can install it using npm or yarn:

bash
npm install typeorm pg

Step 2: Configure TypeORM

Next, you need to configure TypeORM in your application. This is typically done by creating an ormconfig.json file or configuring it directly in your code. In this configuration, you can specify the database type, host, port, username, password, database name, and other important database connection options.

For example, the following is a simple configuration example that uses PostgreSQL:

json
{
  "type": "postgres",
  "host": "localhost",
  "port": 5432,
  "username": "test",
  "password": "test",
  "database": "test",
  "synchronize": true,
  "logging": false,
  "entities": [
    "src/entity/**/*.ts"
  ],
  "migrations": [
    "src/migration/**/*.ts"
  ],
  "subscribers": [
    "src/subscriber/**/*.ts"
  ],
  "cli": {
    "entitiesDir": "src/entity",
    "migrationsDir": "src/migration",
    "subscribersDir": "src/subscriber"
  }
}

Step 3: Connection Pool Configuration

In TypeORM, connection pool configuration is typically managed through the extra option. For example, for PostgreSQL, you can set the maximum connection pool size, etc.:

json
{
  "type": "postgres",
  "extra": {
    "max": 20 // Maximum number of connections
  }
}

Step 4: Initialization and Usage of Database Connection

Once you have configured TypeORM, you can create and use the connection in your code:

typescript
import { createConnection } from 'typeorm';

async function main() {
  try {
    const connection = await createConnection();
    // Use connection for database operations
  } catch (error) {
    console.error('Error connecting to the database', error);
  }
}

main();

Example

For example, suppose we have a User entity and we want to query all users. We can use TypeORM's Repository API to simplify this process:

typescript
import { getRepository } from 'typeorm';
import { User } from './entity/User';

async function findAllUsers() {
  const userRepository = getRepository(User);
  return userRepository.find();
}

In summary, TypeORM provides a very powerful and flexible way to manage database connections, including automatic handling of the connection pool. This allows developers to focus more on implementing business logic rather than worrying about the details of database connection management.