async.queue pause/resume concurrency problem

[i3fox]

In the async.queue I found an issue related to restart after a pause (resume) and I try to fix.
It's not simple to explain, please follow these steps:

1. for concurrency tasks are in execution
2. I pause the queue and wait for the execution of tasks finishes
3. I resume queue
4. Queue restarts but concurrency does not work: only one task is running.

Example of problem:

var async = require("async");
var q = async.queue(function (task, callback) {
    console.log('hello ' + task.name);
    setTimeout(function() {
        callback();
    }, 2000);
}, 5);

q.pause();
q.push({name: '1'});
q.push({name: '2'});
q.push({name: '3'});
q.push({name: '4'});
q.push({name: '5'});
q.push({name: '6'});
q.push({name: '7'});
q.push({name: '8'});
q.push({name: '9'});
q.push({name: '10'});

setTimeout(function () {
    q.resume();
    }, 2500);

[aearly]

Wait -- this calls process() for each task left in the queue, even if there's 2500+ of them? Surely there's a better way to fix the concurrency. Mabye only call process() n times where n = concurrency.

[i3fox]

I think you are right, if the queue contains many tasks the cycle can be heavy.
Could be so:

for (var i = 0; i < q.tasks.length && i < q.concurrency; i++) {
    async.setImmediate(q.process);
}

[aearly]

That would work a lot better.

[caolan]

Can you please add a failing test for this. I think it's a legitimate issue, I just want the patch to be accompanied by a test case.

[elliotbonneville]

Looks like this bug is (still?) appearing in NPM's package, v0.9.0. Any updates since then?

[ralgara]

Still an issue in 0.9.0. In #508, @caolan suggests against calling the callback synchronously. I suppose this means wrapping the callback in either setImmediate or process.nextTick. I have tried both to no avail. Any intention to merge this pull request?

[aearly]

I just added a couple tests for this and it seems to work fine. Am I testing what is causing the issue properly?