[tap1r]

Description

Summary of Changes

The internal key-vault client used by automatic encryption now drops a listener when the application client drops it, and Encrypter.close() detaches the forwarding hooks.

Notes for Reviewers

newListener still forwards every event name, which is the previous behavior, not only MONGO_CLIENT_EVENTS. removeListener matches that set. Listeners that were already attached when getInternalClient ran are copied, and removeListener removes those too, because they are the same function references.

Registering the removeListener hook emits newListener, so that function is also attached to the internal client. close() removes it there directly. Once it has been removed from the application client it cannot observe its own removal.

new Encrypter() constructs AutoEncrypter and can spawn mongocryptd. The unit test calls getInternalClient on an uninitialized instance so the forwarding can be tested without that. close() is covered with a stub autoEncrypter.

Jira: NODE-7986

What is the motivation for this change?

Applications that subscribe to command monitoring for the life of one operation, then remove the listener, kept receiving key-vault traffic and retained the listener for the life of the encrypted client.

For bug fixes

Current (incorrect) behavior:

Removing a listener from the application MongoClient does not remove it from the internal client created for the key vault. Listeners added after the internal client is created are copied on newListener and then left in place. Encrypter.close() does not remove the forwarder.

Expected behavior:

client.removeListener(event, listener) removes that function from the internal client. After encrypter.close(client), new subscriptions on the application client are not copied, and the internal client no longer holds the forwarding function.

How to reproduce:

const client = new MongoClient(uri, { autoEncryption });
const listener = () => {};
client.on('commandStarted', listener);
// getInternalClient has copied listener onto the key-vault client
client.removeListener('commandStarted', listener);
// listener still runs when the key-vault client emits commandStarted

Unit coverage: test/unit/client-side-encryption/encrypter.test.ts.

Affected versions:

Present on main for any client that creates the internal key-vault client (auto-encryption without an explicit keyVaultClient, and with maxPoolSize !== 0). No specific server version.

Double check the following

• Lint is passing (npm run check:lint)
• Self-review completed using the steps outlined here
• PR title follows the correct format: type(NODE-xxxx)[!]: description
  • Example: feat(NODE-1234)!: rewriting everything in coffeescript
• Changes are covered by tests
• New TODOs have a related JIRA ticket

[PavelSafronov]

@tap1r, thank you for taking the time to create this PR! This is tracked in NODE-7986. The team is currently at capacity, so we will be reviewing it over the next few quarters as capacity allows.