KPC
Kevin Powell - Community•6d ago
Faker

Should I start my database connection on server start?

Hello, quick question, I'm working on my back-end code for my product page website. My question is when connecting with my database (mongoDB in this case), I was wondering, as soon as the server starts, should we connect the database and then we just add functions to query it when needed Or we implement a connection string in each function. That is for example, consider this code: 
const { MongoClient } = require('mongodb');

async function runGetStarted() {
  // Replace the uri string with your connection string
  const uri = '<connection string URI>';
  const client = new MongoClient(uri);

  try {
    const database = client.db('sample_mflix');
    const movies = database.collection('movies');

    // Queries for a movie that has a title value of 'Back to the Future'
    const query = { title: 'Back to the Future' };
    const movie = await movies.findOne(query);

    console.log(movie);
  } finally {
    await client.close();
  }
}
runGetStarted().catch(console.dir);
const { MongoClient } = require('mongodb');

async function runGetStarted() {
  // Replace the uri string with your connection string
  const uri = '<connection string URI>';
  const client = new MongoClient(uri);

  try {
    const database = client.db('sample_mflix');
    const movies = database.collection('movies');

    // Queries for a movie that has a title value of 'Back to the Future'
    const query = { title: 'Back to the Future' };
    const movie = await movies.findOne(query);

    console.log(movie);
  } finally {
    await client.close();
  }
}
runGetStarted().catch(console.dir);
The connection happens in the function itself, my concern is should I write something like that or when server starts, run connectDB function then import it when needed to access my database settings?
7 Replies
Faker
FakerOP•6d ago
Reuse Your Client
As each MongoClient represents a pool of connections to the database, most applications only require a single instance of a MongoClient, even across multiple requests. To learn more about how connection pools work in the driver, see the Connection Pools page.
Reuse Your Client
As each MongoClient represents a pool of connections to the database, most applications only require a single instance of a MongoClient, even across multiple requests. To learn more about how connection pools work in the driver, see the Connection Pools page.
Just came across that, any idea why it's more suitable to reuse our client, that is I guess I only need to have a function that runs that connect my database from start?
13eck
13eck•6d ago
Because under the hood MongoClient keeps a pool of connections. It's not just one connection, it's your gateway to multiple connections. This way it can send different requests to different connections and if one connection dies it can spawn a new one without stopping any in-flight connections or grinding all new connections to a halt.
Faker
FakerOP•6d ago
oh ok I see so when we write something like const client = new MongoClient(), under the hood, it's not a single connection being created (I thought it was) but rather it's a pool?
13eck
13eck•6d ago
Most DB ORMs use connection pools yeah
Faker
FakerOP•6d ago
yup, thanks for the insight ! by the way when we re use the client, we don't expect to have some finally block that would close the client?
13eck
13eck•6d ago
You'll have to consult the docs for your ORM to find that out
Faker
FakerOP•6d ago
noted, ty !

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