Cross library interleaving can cause node 10's nextTick limit to be hit.

[taras]

On Node 0.10.33, using RSVP causes deprecation error: (node) warning: Recursive process.nextTick detected. This will break in the next version of node. Please use setImmediate for recursive deferral.

This issue seems to appear and disappear under strange circumstances:

• (node) warning: Recursive process.nextTick detected. This will break in the next version of node. Please use setImmediate for recursive deferral. ember-cli/ember-cli#1859
• (node) warning: Recursive process.nextTick detected. ember-cli/ember-cli#2658

This PR replaces process.nextTick with setImmediate. All tests pass.

[stefanpenner]

nextTick actually isn't deprecated and node 11 has removed this limit. Although setImmediate may not be correct here, we may need to use it in node 10..

[stefanpenner]

cc @domenic

[stefanpenner]

So the issue you see is multiple different RSVP's interacting with each other. This could also be caused by multiple different promises libraries interacting with each other in specific ways.

var A = require('rsvp1').Promise;
var B = require('rsvp2').Promise;

A.resolve().then(function() {
  console.log('first nextTick');
  B.resolve().then(function() {
    console.log('second nextTick');
    A.resolve().then(function() {
      console.log('third nextTick');
    });
  });
});

@taras ^^ if looped 500 or so times will cause the error to happen, likely a great test case to add.

this problem can happen quickly in for example broccoli were depending on the topology of node_modules, we can easily have a large number of rsvp's floating around

[stefanpenner]

I wonder actually if joliss/promise-map-series#4 may mitigate this problem.

I'll have to investigate the exact scenario in broccoli in broccoli that builds this specific problem

[stefanpenner]

via @domenic

in node 11:

nodejs/node@0761c90
nodejs/node@0761c90

[stefanpenner]

i suspect everyone else also has this problem, even though asap guards. It can't possibly guard when interleaving with other libraries occurs.

bluebird:
https://github.com/petkaantonov/bluebird/blob/master/src/schedule.js#L5-L9
https://github.com/petkaantonov/bluebird/blob/master/src/async.js#L55-L67

when:
https://github.com/cujojs/when/blob/25b3c0ad06292d3d46ca27966cc026407eaa2184/lib/env.js#L25

asap:
https://github.com/kriskowal/asap/blob/master/raw.js#L86-L96

[stefanpenner]

@taras i have a test scenario you can implement.

[taras]

@stefanpenner got it, I'll work on that.

[stefanpenner]

@taras thank you sir :)

[stefanpenner]

btw the sky is falling :P

[stefanpenner]

lets do this only if node is < 0.11.0

[taras]

This deprecation was introduced in 0.10.0. Should I make this change for 0.10.x?

[taras]

It took me too long to figure out that "the sky is falling" means that it's time sensitive :) I'm working on it now.

[taras]

I'm having a hard time replicating the error with your code example. Can you give me a gist with code that you used to cause the deprecation to show up?

[taras]

@stefanpenner I pushed a bit of WIP code to show you what I've been trying.

Note: I'm manually copying the dist/rsvp.js to dist/rsvp-2.js to give me another module to work with.

[stefanpenner]

var A = require('rsvp1').Promise;

A.resolve().then(function() {
  console.log('first nextTick');
   process.nextTick(function() { // <-- should be sufficient i think
    A.resolve().then(function() {
      console.log('third nextTick');
    });
  });
});

[taras]

Here is the test that I tried, but I wasn't able to get it show the deprecation warning.

describe("on node 0.10.x, using process.nextTick recursively shows deprecation warning. setImmediate should be used instead.", function() {
  // (node) warning: Recursive process.nextTick detected. This will break in the next version of node. Please use setImmediate for recursive deferral.

  specify("should not throw an error", function (done) {
    var promises = [];

    for (var i = 0; i < 1000; i++) {
      var promise = new Promise(function(resolve){
        RSVP.resolve().then(function() {
          process.nextTick(function() { // <-- should be sufficient i think
            RSVP.resolve().then(function() {
              process.nextTick(function(){
                RSVP.resolve().then(function() {
                  resolve();
                });
              })
            });
          });
        });
      });
      promises.push(promise);
    }

    RSVP.all(promises)
        .then(function(){
          done();
        });
  });

});

[stefanpenner]

ya that inner tree needs to have a depth of 1000, not repeating the whole thing 1000 times.

[taras]

Got it.

The following code causes warnings to be displayed.

describe("on node 0.10.x, using process.nextTick recursively shows deprecation warning. setImmediate should be used instead.", function() {
  // (node) warning: Recursive process.nextTick detected. This will break in the next version of node. Please use setImmediate for recursive deferral.

  specify("should not throw an error", function (done) {
    var depth = 0;
    var nextTick = function(promise) {
      if (depth < 500) {
        promise.then(function(){
          process.nextTick(function(){
            console.log('nextTick: ' + depth);
            depth++;
            nextTick(promise);
          })
        });
      }
      return promise;
    };

    nextTick(RSVP.resolve())
        .then(function(){
          done();
        });
  });
});

When I apply this code to async.js, the warnings go away.

function useNextTick() {
  var nextTick = process.nextTick;
  // node version 0.10.x displays a deprecation warning when nextTick is used recursively
  // setImmediate should be used instead instead
  var version = process.versions.node.match(/^(?:(\d+)\.)?(?:(\d+)\.)?(\*|\d+)$/);
  if (Array.isArray(version) && version[1] === '0' && version[2] === '10') {
    nextTick = setImmediate;
  }
  return function() {
    nextTick(flush);
  };
}

Now, I gotta figure out how to capture output.

[taras]

I don't need to capture output to get deprecation errors because that test will cause RangeError: Maximum call stack size exceeded when setImmediate is not used.

If that's ok, then you can look at the code.

[taras]

Grr... it looks like the test doesn't run 500 times with setImmediate. I'm going to look into it further. Sorry.

[taras]

@stefanpenner ok, I got it sorted out. I verified that my new test code creates a recursion 1000 levels deep. With original code, the test fails because an exception is thrown. The tests passes on the new code.

I also added node 0.11.x to travis.

[stefanpenner]

@taras awesome this looks fantastic. I really appreciate you digging into this!

[taras]

It's my pleasure. Glad I could help out.

[soulcutter]

Great tag team work, big ups for getting to the bottom of this.