DDP shows method result, but await Meteor.callAsync just hangs

help
1

Meteor 3.0.4, React 18.3.1, using hooks

Typical situation where a button click event runs a function, which calls a method:
<button onClick={() => save()}>Save</button>
Then

const save = async () => {
  try {
    console.log('Calling method');
    await Meteor.callAsync('save', update);
    console.log('Done');
  }
  catch (error) {
    console.log(error);
  }
}

What’s crazy is that I can click that button over and over, and sometimes it works fine, sometimes it hangs on the ‘await’ line, and I never see the ‘Done’ message. It just hangs.

When I look at the DDP traffic in the Meteor Dev Tools, I see the method being called, and a split second later I see the method’s return (which I would expect to resolve the Meteor.callAsync promise and move on to the console.log(‘Done’)).

I know this isn’t a lot of detailed information about my issue, but I’m wondering if anyone has noticed a similar issue after upgrading to Meteor 3.

I see in the 3.1 changelog:

  • Solve remaining issues with Top Level Await and Reify

And wondering if this particular item might be related to unreliable promise resolution in Meteor.callAsync

2

The way you wrote the example, you are awaiting for a result that you don’t actually use. Does this help for Optimistic UI? I never use stubs so I am not sure what is the intent in your code.

How about this?

const save = () => {
  Meteor.callAsync('save', update)
    .then(res => {
      // do something with res or don't use .then() if you are not expecting anything to return
       console.log('Done'))
     }
    .catch(err => console.log(err))
}
3

Thanks for your reply. I just outlined roughly what’s going on. I do, in fact, assign the awaited value to a variable an use it after (of course, when the issue manifests, execution never passes below the await).

I’m currently rolling back to meteor 2.16, with all other code the same. I think this might help me determine if the issue is fundamentally something related to meteor3, or if it’s something in my code. I’ll report back here when I know.

4

I downgraded to meteor 2.16, and I’m running the identical code as before, and it no longer hangs while awaiting a meteor method call.

This suggests that there is an issue with meteor 3 and async/await on method calls. Once things settle over here, I’m going to try upgrading to meteor 3.1 (whose changelog states the fixing of some issue related to top-level await), and will report here if the issue is resolved in that version.

5

If you can create a simple reproduction code that can exhibit the behavior, that can immensely help check what’s happening.

6

I wish I could, but the tricky part is that the issue only happens in our production environment, and it seems to be worse during the day (higher traffic/load). What makes even less sense, is that it looks like a client-side-only issue, because the server clearly successfully completing the method call, and it’s doing so quite quickly (~50ms)…we see this in our server logs, and it’s confirmed client size in the DDP dev tools.

Edit: I should clarify that this never happens in our staging environment, which is an architectural/infrastructural clone of production.

7

did you try to add this.unblock() to your method?