Live queries, multiple subscription at once, is it me or it's not implemented at the moment?

[avielfedida]

Hello everyone, I'm using the JS-SDK(v1.8.4) with Parse-server(v2.2.9), I tried to subscribe to multiple queries at the same app page, I've noticed that for example:

If I subscribe only to Query A, I can later unsubscribe(as in using the method) from Query A and all is good(no further events will emitted), but If I subscribe to Query A, then I again subscribe to Query B, and now I want to unsubscribefrom Query A, I can't, events will still emitted.

If I subscribe to A then B, now I unsubscribe from B, no no further events will emitted for B, but I can't unsubscribe from A, I can call unsubscribe but events for A will emitted.

I don't know if this supposed to work like that(not implemented feature), anyway I just wanted to know if its a valid behavior?, for now the workaround is to delete the event from the subscription object, for example:

let subscription = (new Parse.Query('ObjectName')).subscribe();
subscription.on('create', data => {})
delete subscription ._events.create;

In the A, B case, you could use unsubscribe for B and delete for A.

Update:

To be more specific, if I have multiple queries subscribed to the same class, I can unsubscribe from both of them successfully, so it reduces the problem to a case where I have 2 queries with 2 different classes, if ever implemented?

[tyleralves]

I know this is a super old issue, but I'm seeing the same bizarre behavior.

this.subscriptionA = queryA.subscribe();
this.subscriptionB = queryB.subscribe()

this.subscriptionA.unsubscribe();  // Fails, subscription to queryA remains active
this.subscriptionA = queryA2.subscribe();
this.subscriptionA.unsubscribe(); // Succeeds; 
// --> subscription to queryA2 is closed, but subscription to queryA remains active of course

[tyleralves]

This happens because the sdk manages a live query client for you if you don't start your own manually. Unfortunately the subscribe method doesn't return a promise, or wait for the live query client to finish initializing before returning. So when you call subscribe multiple times in a row, it just overwrites the default LiveQueryClient repeatedly, leaving your previous listeners as zombies.

Workaround:
Manually create a LiveQueryClient
See: http://docs.parseplatform.org/js/guide/#livequeryclient
Note: You must manually change your server url to ws:// or wss://

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[dplewis]

@acinader Thoughts on this one? Maybe create a subscribeAsync() function.

Also just realized that you can't pass sessionToken into query.subscribe();

[acinader]

Certainly sounds like an issue for any reasonably complex use.

Step one would be failing unit tests for his example. Not sure what the implementation would be as I am not familiar with that bit of code (yet ;)), but this is a clearly written issue with enough info to create failing tests, which would like lead to the solution being apparent?

[Amphaal]

Hi guys,

It's been a long time since i haven't played with Parse but I think I can help.

I had trouble back in 2018 to make livequeries work well with a moderately complex project involving React-native / Redux / RxJS : looking at our PA issue, it's seems related to my old concerns.

Following my proposal on #533 , i did a hasty fix on LiveQuerySubscription.js and ParseLiveQuery.js, modifying the open/close/subscribe/unsubscribe methods. It fixed everything if i remember correctly.

I can, if you like, try a diff and propose a merge.

[dplewis]

@Amphaal That would be great! I looked at your proposal and you found the root cause.