How to set useMongoClient in mongoose?

In an earlier version of Mongoose (prior to 4.x and 5.x), the useMongoClient option was introduced to manage database connections. This option was primarily used to ensure the new MongoDB driver's connection management logic is employed. Starting from Mongoose 5.x, the useMongoClient option is no longer necessary or supported, as the new MongoDB driver is now the default connection method.

Example (Using Mongoose 4.x Version)

If you are using Mongoose 4.x and want to ensure the new MongoDB driver logic is utilized, you can do the following:

javascript
var mongoose = require('mongoose');

// Use the `mongoose.connect()` method to connect to the local database `myapp`, explicitly passing `{ useMongoClient: true }` to enable the new connection logic.
mongoose.connect('mongodb://localhost:27017/myapp', { useMongoClient: true });

mongoose.connection.on('connected', function () {
    console.log('Mongoose default connection open to myapp');
});

mongoose.connection.on('error', function (err) {
    console.log('Mongoose default connection error: ' + err);
});

In this code snippet:

• We first import the mongoose module.
• Use the mongoose.connect() method to connect to the local database myapp, explicitly passing { useMongoClient: true } to enable the new connection logic.
• Then, we set up event listeners to monitor connection status, such as the connected and error events.

Using Mongoose 5.x or Higher

In Mongoose 5.x or higher versions, you can connect directly without useMongoClient:

javascript
var mongoose = require('mongoose');

// Connect directly without `useMongoClient`
mongoose.connect('mongodb://localhost:27017/myapp');

mongoose.connection.on('connected', function () {
    console.log('Mongoose connection open to myapp');
});

mongoose.connection.on('error', function (err) {
    console.log('Mongoose connection error: ' + err);
});

In this example, we removed { useMongoClient: true } as it is no longer necessary or supported. The rest remains similar, with event listeners set up to monitor and handle potential events or errors.

Summary

Therefore, if you are currently using or maintaining a project that relies on an older version of Mongoose and uses useMongoClient, you should consider updating your Mongoose version to leverage the new default settings and performance improvements. If you are already using Mongoose 5.x or a newer version, you do not need to worry about useMongoClient, as it is integrated into the connection logic.