What problem are you facing?

When the MONGODB-AWS auth mechanism is selected, and credentials are not provided upfront, the auth mechanism will try loading credentials from the EC2 metadata service.

The problem is that the intended 10-second timeout is not programmed properly, so the auth mechanism will hang for more than a minute if attempted outside of EC2.

On my machine I'm seeing a delay of 75 seconds before the connection attempt fails.

Additionally, a timeout as low as 3 seconds may be more desirable to improve user experience.

This issue seems to also impact "mongosh".

What driver and relevant dependency versions are you using?

node v17.8.0

mongodb@4.5.0

mongosh 1.3.1

Steps to reproduce?

Within nodejs:

import { MongoClient } from "mongodb";

MongoClient.connect("mongodb+srv://some-stuff-here.mongodb.net", {
  authSource: "$external",
  authMechanism: "MONGODB-AWS",
});

 With mongosh:

$ mongosh "mongodb+srv://some-stuff-here.mongodb.net?authSource=%24external&authMechanism=MONGODB-AWS" --apiVersion 1Connecting to:          mongodb+srv://......etc.......

Note that the issue only occurs when you do not have credentials in the environment and are not on EC2.
In both cases, this error is given after 75 seconds:

Error: connect ETIMEDOUT 169.254.169.254:80

Comparison with AWS SDK

I'd like to point out that the official AWS SDK JS only waits 3 seconds before giving up on a credential fetch. It issues up to 3 requests with a 1-second timeout on each request. Source: https://github.com/aws/aws-sdk-js/blob/8d6429f810abb24895a248b486746ffae92eedfb/lib/credentials/ec2_metadata_credentials.js#L12-L13

Logic fault details

This StackOverflow entry shows how HTTP timeouts work in NodeJS: https://stackoverflow.com/questions/6214902/how-to-set-a-timeout-on-a-http-request-in-node

Effectively, the timeout registered here does not have any effect on its own: https://github.com/mongodb/node-mongodb-native/blob/067fa077b6e3be266844b6f1c7ba1f34fd882917/src/cmap/auth/mongodb_aws.ts#L258

To enforce the timeout, this line of code can be added later in the function:

req.on('timeout', () => req.destroy());