Node domains only work when then-ing resolved promised

[tp]

I am experiencing some issues around node domains and the timing of when then is called on a Promise.

Basically, all continuations created before the Promise is resolved loose their domain, and everything created after the Promise is resolved stay in the same domain.

var Promise = require('rsvp').Promise;
var request = require('request');

var p = new Promise(function(resolve, reject) {
  request('http://www.google.com', function(err, response, body) {
    console.log('done loading google.com')
    resolve(response.statusCode);
  });
});

var domain = require('domain');

var x = 0;

var f = function() {
  var id = ++x;
  console.log('%d waiting',id);

  var d = domain.create();

  process.domain = d;
  process.domain.x = 1;
  p.then(function(result) {
    console.log('%d continues',id);
    console.log('result = %d', result); 
    console.log('process.domain? %s', !! process.domain);
  });
};

f();
process.nextTick(f);
setTimeout(f, 100);
setTimeout(f, 1000); // set the timeout high, so that it surely fires after google.com has loaded

Output:

1 waiting
2 waiting
3 waiting
done loading google.com
1 continues
result = 200
process.domain? false
2 continues
result = 200
process.domain? false
3 continues
result = 200
process.domain? false
4 waiting
4 continues
result = 200
process.domain? true

As you can see, only the continuation that was created after the Promise had already been resolved works correctly.

[stefanpenner]

thanks for reporting this.

related solution on another library: petkaantonov/bluebird#152
Seems like implementing that here is the correct step

I should have time an evening this week, but if someone beats me to it, I'll be forever indebted.

[domenic]

There's a simpler solution, just call process.nextTick every time instead of saving in a var.

[stefanpenner]

@domenic orly?

[stefanpenner]

@domenic im a domain noob, but I don't think that is a problem as process.nextTick isn't being saved to a var, unless closing of process itself is the problem. I believe it's the optimization of 1 nextTick per run to completion.

[stefanpenner]

I believe I have a clear grasp on the issue and the solution. I'll likely through together a good set of tests, and work on this at some point when i have time.

[stefanpenner]

Sorry I haven't gotten to this yet, I will try to soon.

[stefanpenner]

as domains are stability 2 and the performance implications of doing this naively are non-trivial this is honestly pretty low priority for me.

[stefanpenner]

@domenic i'll implement this if you tell me i should (with good reason)

[domenic]

Nah

---

From: Stefan Pennermailto:notifications@github.com
Sent: ý2014-ý09-ý30 02:08
To: tildeio/rsvp.jsmailto:rsvp.js@noreply.github.com
Cc: Domenic Denicolamailto:domenic@domenicdenicola.com
Subject: Re: [rsvp.js] Node domains only work when then-ing resolved promised (#239)

@domenichttps://github.com/domenic i'll implement this if you tell me i should

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Reply to this email directly or view it on GitHubhttps://github.com//issues/239#issuecomment-57253984.