Connection pooling concept in Node.js - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the connection pool module.

Node.js

const { Pool } = require('[1]');

Drag options to blanks, or click blank then click option'

Aexpress

Bpg

Cfs

Dhttp

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'express' instead of 'pg' for database connections.

Using 'fs' which is for file system operations.

The pg module is used for PostgreSQL connection pooling in Node.js.

2fill in blank

medium

Complete the code to create a new connection pool with a max of 10 connections.

Node.js

const pool = new Pool({ max: [1] });

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A5

B20

C1

D10

Attempts:

3 left

💡 Hint

Common Mistakes

Setting max to 1 which limits concurrency.

Using a very high number like 20 unnecessarily.

The max option sets the maximum number of connections in the pool. Here, it is set to 10.

3fill in blank

hard

Fix the error in releasing the client back to the pool.

Node.js

client.[1]();

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Arelease

Bend

Cclose

Ddisconnect

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'close' which closes the connection instead of releasing it.

Using 'end' which terminates the client.

To return a client to the pool, you must call release(). Other methods close or end the connection permanently.

4fill in blank

hard

Fill both blanks to query the database and release the client properly.

Node.js

pool.connect().then(client => {
  return client.query([1])
    .then(res => {
      client.[2]();
      return res;
    });
});

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A"SELECT * FROM users"

B"DELETE FROM users"

Crelease

Dclose

Attempts:

3 left

💡 Hint

Common Mistakes

Using DELETE query which removes data instead of fetching.

Calling 'close' instead of 'release' on the client.

The query string should be a SELECT statement to fetch data. The client must be released with release() after the query.

5fill in blank

hard

Fill all three blanks to create a pool, query data, and handle errors properly.

Node.js

const pool = new Pool({ max: [1] });

async function fetchData() {
  const client = await pool.connect();
  try {
    const result = await client.query([2]);
    return result.rows;
  } catch (err) {
    console.error([3]);
  } finally {
    client.release();
  }
}

Drag options to blanks, or click blank then click option'

A5

B"SELECT * FROM products"

Cerr

D10

Attempts:

3 left

💡 Hint

Common Mistakes

Setting max to 5 which is lower than intended.

Logging a wrong variable name instead of the error.

Using a wrong query string.

The pool max connections is set to 10. The query fetches all products. Errors are logged using the caught error variable err.