Upon upgrading the driver from version 3.6 -> 4 according to the change documentation (https://github.com/mongodb/node-mongodb-native/blob/4.1/docs/CHANGES_4.0.0.md) one of the removed deprecations is:

"Remove MongoClient.isConnected - calling connect is a no-op if already connected" 

If I am reading that correctly, you are suggesting that if there is already an open mongo connection when ".connect()" is called again it will return the exact connection that is already open?

I am raising this as when I have tried to achieve this locally I have not seen this to be the case... I have seen another connection opened.

Another point to my case is this line (https://github.com/mongodb/node-mongodb-native/blob/4.1/src/operations/connect.ts#L28) inside the connect function, suggests that the connection should be re-used if a connection already exists. However if you were to console "mongoClient.topology" you would receive undefined at this point (The mongoClient does not have a topology object), hence that if block will not be called.

Please see a little sample below:

async function getClient2(close) { const client = await MongoClient.connect("mongodb://localhost:27017/", {"useNewUrlParser": true, "useUnifiedTopology": true}); // , {"useUnifiedTopology": true} if(close) { await client.close(); }} async function execute() { await getClient2(); await getClient2(true);}execute();

This code will open 2 separate connections, rather than re-use the first connection.

Maybe I am misunderstanding something around this, but any information on this would be much appreciated.

Also apologies if I have not added the correct labels / links / tags.