Promise in core-js doesn't work with domain in nodejs

[Jiaji Zhou]

I use domain in nodejs to store data related to an async chain. Below is the code to demonstrate the concept.

in index.js

require('babel/register');
require('./server');

in server.js

import express from 'express';
import domain from 'domain';
import crypto from 'crypto';

const app = express();

app.use((req, res, next) => {
  const requestDomain = domain.create();
  requestDomain.add(req);
  requestDomain.add(res);
  requestDomain.trackingId = crypto.randomBytes(16).toString('hex');
  requestDomain.run(() => {
    next();
  });
});

app.get('/user/:id', (req, res) => {
  const trackingId = process.domain.trackingId;
  new Promise((resolve) => {
    setTimeout(resolve, 1000);
  }).then(() => {
    if (process.domain.trackingId !== trackingId) {
      throw new Error('ahhh, domain messed up!');
    }
    res.status(200).json({
      user: req.params.id,
    });
  }).catch((err) => {
    console.log(err.message);
    res.status(500).json(err.stack);
  });
});

app.listen(3000, () => {
  console.log('server started');
});

So the idea is when a request is being handled by express, a trackingId will be generated and bound to a domain scoped to the current request. According to nodejs' documentation process.domain will then always refer to that domain object during the whole async process chain.

In the code I added a check to verify that the trackingId is the same after the promise is resolved. However when I use the Promise provided by babel (core-js implementation) the Error will be thrown. So actually, somehow the Promise breaks the domain scope.

I then replace the Promise implementation with the bluebird one, everything then works well. Essentially, I changed the index.js to

require('babel/register');
global.Promise = require('bluebird');
require('./server');

So it looks like the Promise in core-js has some problem with nodejs' domain. Although I currently have a workaround on this, I think it might be good if someone can look at it.

[Denis Pushkarev]

Problems with domains probable, but I can't reproduce it with your example - process.domain.trackingId === trackingId in io.js with replaced Promise. Please, write simple reproduceble example or change current and I will fix it.

[Jiaji Zhou]

Hi @zloirock ,
Thanks for looking into this. Sorry that the description is not clear enough.
The example will reproduce when you use a concurrent client to stress it.

Below, I give a self-contained test file.

var domain = require('domain');
var core = require('core-js/library');
var crypto = require('crypto');
var Promise = require('bluebird');

console.log(process.version);

function runInDomain(fn) {
    var d = domain.create();
    d.run(fn);
}

var counter = 0;

function test() {
    runInDomain(function() {
        process.domain.trackingId = crypto.randomBytes(16).toString('hex');
        var trackingId = process.domain.trackingId;
        console.log('>' + trackingId);
        // NOTE: replace core.Promise with Promise, the error will disappear.
        new core.Promise(function(resolve) {
            setTimeout(resolve, 100);
        }).then(function() {
            console.log('<' + process.domain.trackingId);
            if (trackingId !== process.domain.trackingId) {
                console.log('error!');
            }
            counter++;
        });
    });
}

var loop = 5;

for (var i = 0; i < loop; ++i) {
    test();
}

setTimeout(function() {
    if (counter !== loop) {
        console.log('error, count not match');
    }
    console.log(counter);
}, 1000);

I tested it with node v0.10, 0.12, iojs 3.2.0, all show the same result. One example below.

$ node test
v0.10.39
>49888ebe680e1cdfe8825adc7d0055ae
>738516ee1d0dba70e3d72e2e8adf698b
>43c6f69e9540290ba0845c8af6927b61
>0053bf12104b660b946cd9b1e84e7b0f
>19c2f270905533ccebd0cfefe20d3805
<49888ebe680e1cdfe8825adc7d0055ae
<49888ebe680e1cdfe8825adc7d0055ae
error!
<49888ebe680e1cdfe8825adc7d0055ae
error!
<49888ebe680e1cdfe8825adc7d0055ae
error!
<49888ebe680e1cdfe8825adc7d0055ae
error!
5

Result after I replace with bluebird Promise

$ node test
v0.10.39
>980ef244549447a874b4b62b45fe3f1b
>19006bc9b4872d950957e41fcb592a92
>d3d536bf058dcb68e82fef1cbf136d64
>fb8d3c8fba1cfc55e7989a258e3706a9
>5b56f5823009500b860e9d5f15004ff3
<980ef244549447a874b4b62b45fe3f1b
<19006bc9b4872d950957e41fcb592a92
<d3d536bf058dcb68e82fef1cbf136d64
<fb8d3c8fba1cfc55e7989a258e3706a9
<5b56f5823009500b860e9d5f15004ff3
5

[Denis Pushkarev]

Thanks! This commit should fix current problem. IIRC with domains possible another problems, any ideas about it?

[Jiaji Zhou]

The fix works great! Thanks!
I don't have more cases that are broken due to domains. I'll create issue here if I found more problems.