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Size discrepancy between queue.workersList().length and queue.running() #1428

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dstibrany opened this issue Jun 6, 2017 · 1 comment
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@dstibrany
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@dstibrany dstibrany commented Jun 6, 2017

What version of async are you using?
2.4.1
Which environment did the issue occur in (Node version/browser version)
Node v4.6.0
What did you expect to happen?
queue.workersList().length should be the same size as queue.running()
What was the actual result?
They sometimes are not the same length.

I'm observing a discrepancy between queue.workersList().length and queue.running(). It looks like lib/internal/queue.js line 60 may be the culprit. Shouldn't we always be splicing exactly one element here instead of potentially many elements. So replacing:

workersList.splice(index)

with

workersList.splice(index, 1)

@hargasinski
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@hargasinski hargasinski commented Jun 7, 2017

Hey Dave, thanks for the report!

I believe you are right. According to the QueueObject docs workersList() should return

the array of items currently being processed.

which is not the case right now:

var q = async.queue(function(task, cb) {
    async.setImmediate(function() {
        console.log(`Processing ${task.name}`);
        console.log(q.workersList());
        console.log(q.running());
        cb();
    });
}, 2);

q.push({name: 'foo'});
q.push({name: 'bar'});
q.push({name: 'baz'});

gives

Processing foo
[ { data: { name: 'foo' },
    callback: [Function: noop],
    next: null,
    prev: null },
  { data: { name: 'bar' },
    callback: [Function: noop],
    prev: null,
    next: null } ]
2
Processing bar
[ { data: { name: 'baz' },
    callback: [Function: noop],
    prev: null,
    next: null } ]
2
Processing baz
[ { data: { name: 'baz' },
    callback: [Function: noop],
    prev: null,
    next: null } ]
1

as opposed to the expected (with workersList.splice(index, 1)):

Processing foo
[ { data: { name: 'foo' },
    callback: [Function: noop],
    next: null,
    prev: null },
  { data: { name: 'bar' },
    callback: [Function: noop],
    prev: null,
    next: null } ]
2
Processing bar
[ { data: { name: 'bar' },
    callback: [Function: noop],
    prev: null,
    next: null },
  { data: { name: 'baz' },
    callback: [Function: noop],
    prev: null,
    next: null } ]
2
Processing baz
[ { data: { name: 'baz' },
    callback: [Function: noop],
    prev: null,
    next: null } ]
1

Thanks for debugging the issue.

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