Mongoose doesn't reconnect after receiving specific mongo events

Prerequisites

• I have written a descriptive issue title
• I have searched existing issues to ensure the bug has not already been reported

Mongoose version

6.5.0

Node.js version

14.19.3

MongoDB server version

4.2.21

Description

Recently upgraded to Mongoose 6 from 5 and getting the following behavior:

I get the following 2 events from Mongo: serverDescriptionChanged with type of Unknown topologyDescriptionChanged with type of ReplicaSetNoPrimary

Looking at the code in mongoose, these 2 events fall on both setting the state to disconnected and no reconnection is attempted: https://github.com/Automattic/mongoose/blob/ba323df0b2c56ba76ff81bd67b4dbac5f6f78c01/lib/connection.js#L877-L915

Is there a reason why this case would require to manually initiate a reconnect?

Steps to Reproduce

1. Start a mongoose connection
2. Receive/trigger serverDescriptionChanged with type of Unknown and topologyDescriptionChanged with type of ReplicaSetNoPrimary
3. Mongoose disconnects and no reconnect is attempted

Expected Behavior

A reconnection would be triggered

[david-badalov]

“Is there a reason why this case would require to manually initiate a reconnect?” No. In Mongoose 6, you never need to manually reconnect. The ‘disconnected’ event is just for monitoring and debugging.

What makes you think that Mongoose disconnects and no reconnect is attempted?

After upgrading to mongoose 6 I see a recurring heartbeat failure and the aforementioned events (this does not happen with mongoose 5). Following these events and mongoose setting the disconnected state my queries start failing:

I start getting the following errors if buffering is enabled:

"kind":"MongooseError","message":"Operation `-.findOne()` buffering timed out after 10000ms"

and a different error if it is not:

MongooseError: Cannot call `-.findOne()` before initial connection is complete if `bufferCommands = false`. Make sure you `await mongoose.connect()` if you have `bufferCommands = false`.

[github-actions[bot]]

This issue was closed because it has been inactive for 19 days since being marked as stale.