MeteorJS connection delay issues

Question

i'm completely new to MeteorJS, just looking at demos and poking around. it is possible that i'm just missing something really basic. i'm using meteor with angular-ui-router. if i start with a state that loads data into a controller, i run into issues because DDP has not initialized yet. this is similar to what was described in Meteor: How can I tell when the database is ready?

relevant part of routing config:

        resolve: {
            location: ($stateParams) => {
                console.log('find', $stateParams);

                let handle = setInterval(function () {
                    console.log(Meteor.status().connected, Meteor.status().status);
                    console.log( !!Locations.findOne({code: $stateParams.code}) ? 'found' : 'not found' );
                }, 100);

                setTimeout(function () {
                    clearInterval(handle);
                }, 2000);

                console.log(Meteor.status().connected, Meteor.status().status);
                return Locations.findOne({code: $stateParams.code});
            }
        }

and the output is

false "connecting"
false "connecting"
not found
true "connected"
not found
true "connected"
not found
true "connected"
found
true "connected"
found

my question is: do i understand correctly that the problem here is that for things to work as expected they must happen in this sequence:

1. web socket connection is initiated
2. web socket connection is ready to use
3. minimongo is refreshed
4. collection.findOne

and 4. is running before 3? if so, what is the suggested workaround?

cross-post: https://github.com/meteor/meteor/issues/9127

Answer 1

Whenever you subscribe in Meteor you should check to see if the subscription is ready before rendering the results. Typically you'd show a spinner when it's not.

const mySub = Meteor.subscribe('somePublication');
if (mySub.isReady()) {
  ... you can access the data using minimongo
} else {
  ... not so fast Jack
}

DDP's websocket connection needs to be up before pub-sub can transfer data but that's not a very significant source of delay in most cases.

You can catch the event when a publication becomes ready in a Tracker.autorun():

const mySub = Meteor.subscribe('somePublication');

Tracker.autorun(() => {
  if (mySub.ready()) ... do something
});

OR in a callback from the subscription:

Meteor.subscribe('somePublication',() => {
  ... subscription is ready
});