Lazy initialization of observers

[laidinidis]

Is there a way to initialize observers lazily?
When I'm doing

ReactiveAggregate(this, Collection, [
    { $match: selectors },
    { $group: { ... } }
  ], {
  debounceCount: 100,
  debounceDelay: 1000,
  noAutomaticObserver: true,
}

the pipeline runs really fast, but if I add an observer it's slow

ReactiveAggregate(this, Collection, [
    { $match: selectors },
    { $group: { ... }}
  ], {
  debounceCount: 100,
  debounceDelay: 1000,
  noAutomaticObserver: true,
  observers: [
    Collection.find(selectors)
  ]
}

What I want is to run the pipeline, get the results and then initialize the observers.

[robfallows]

@laidinidis : I converted this issue to a Q&A discussion.

Great question!

It should be possible to wrap the observer setup in a Meter.defer or Meteor.setTimeout to make that asynchronous. Everything else should catch up after that. That will need testing because it's untried.

Note that in your first example, the pipeline will not re-run reactively since you do not specify any observers and you have noAutomaticObserver: true. That is basically a "run once" configuration. Using a debounceDelay: 1000 value will alter the behaviour to "run every second".

At the moment my time is limited, so if you think you can help with a PR, that would be great. Otherwise, I'll find some time over the next couple of weeks to test.

[robfallows]

Awesome! I'll try and get round to issuing a new release later today.

Thanks for the confirmation 🙂

[robfallows]

New release now published.

[robfallows]

@laidinidis : Please see #55, which is showing poor performance from asynchronous observer initialisation.

I wonder if you can run a similar test with debug: true in the options and paste the console output here, please?

[robfallows]

@laidinidis : There have been some reports of serious performance issues with v1.3.5 and I have reverted the changes for asynchronous observer set up for v1.3.6. If v1.3.5 is working for you without issue, then you can continue to use it for the forseeable future, but you should pin the version or any update will change behaviour.

[laidinidis]

Hi Rob, sorry I didn't reply earlier, I was on vacation.
To be honest I didn't notice any performance issues or improvements on production. I'm guessing i'll be fine with the new version.
Thanks for the heads-up.