connection event open is not equivalent to connected

[mpodolsk]

its either a bug or bad documentation.

mongoose.connection emitted connected but never open.

as per docs

open: Equivalent to connected

I used in my app connected event as a ready signal to make sure my app was ready to receive traffic.

what ended up happening is that the app was receiving traffic it was not able to service.

the open event was never emitted and I think that is the one needed for mongoose to operate properly?

Looking at the source code, open and connected are not exactly identical. It would be nice to note the difference even if they are subtle.

    "mongoose": "^5.13.10",

[IslandRhythms]

const mongoose = require('mongoose');


async function test() {
    await mongoose.connect('mongodb://localhost:27017/', {useNewUrlParser: true,
    useUnifiedTopology: true,});
    await mongoose.connection.dropDatabase();
}

mongoose.connection.on('open', () => {
    console.log('open fire');
});

mongoose.connection.on('connected', () => {
    console.log('connected successfully');
});

test();

[IslandRhythms]

If there is a slight difference, I think we should mention that in the docs.

[mpodolsk]

from the source code is can see there are some differences

@event connected: Emitted when this connection successfully connects to the db. May be emitted multiple times in reconnected scenarios.

@event open: Emitted after we connected and onOpen is executed on all of this connections models.

https://github.com/Automattic/mongoose/blob/master/lib/connection.js#L642
https://github.com/Automattic/mongoose/blob/master/lib/connection.js#L45
https://github.com/Automattic/mongoose/blob/master/lib/connection.js#L46

Also in the code I can see the reconnect event is triggered differently for replica sets.
is there some documentation explaining how and when we emit reconnect when using replicaSet

[vkarpov15]

@mpodolsk there's a note here about connection events in replica sets:

"In a replica set, Mongoose will emit 'disconnected' if it loses connectivity to the replica set primary, and 'connected' if it manages to reconnect to a the replica set primary."