LiveQuerySubscription "open" event does not fire as expected

[travsr]

Issue Description

When I register an open event for a LiveQuerySubscription, the event does not fire on the intial websocket subscribed event as you'd expect. However, if it does fire if a reconnect happens.

My guess is the fact that you now have to wait for the subscription object to be returned via promise from query.subscribe() may be the cause. By the time you are able to register your event, the "open" event will already have been emitted by LiveQueryClient.

My quick fix was to add a slight timeout delay before the open event is emitted in LiveQueryClient.js, but that seems like more of a hack than a real solution.

Maybe I was just doing something wrong but this seemed like something potentially worth posting here.

Test Case

let query = new Parse.Query("MyClass");
let subscription = await query.subscribe();

subscription.on('open', (response) => {

    // (the stuff in here will not run)
    console.log("SUBSCRIPTION OPENED"); // <-- does not print to console
   
});

To accurately reproduce your issue. Add your test cases here and read the Contributing Guide to run the tests.

Environment Setup

• Server

  • parse-server version (Be specific! Don't say 'latest'.) : ^4.2.0
  • Operating System: macOS 10.15.4
  • Localhost or remote server?: Localhost

• JS SDK

  • JS SDK version: ^2.12.0
  • Application?: Browser

Logs/Trace

[dplewis]

You brought up an interesting point. The point of waiting for the subscription is to ensure the connection is successful, resulting in the open event to not fire.

We should remove it from the documentation.

@acinader @davimacedo Thoughts?

[dplewis]

@travsr Can you post your quick fix? I'm curious on how you got it to work.

[davimacedo]

@dplewis what do you want to remove from the docs? The open event?

[dplewis]

@davimacedo Hmm we could add a slight delay here. This will allow client time to set an Open Event and possibly the same for Error event.

[davimacedo]

Yes. Just setTimeout(() => subscription.emit(SUBSCRIPTION_EMMITER_TYPES.OPEN, response)); should do the magic.

[travsr]

@dplewis @davimacedo Yep that's exactly where I added it in my code as well :) I used 200 ms and it hasn't given me issues so far.