async.queue and concurrency

[fprivitera]

if I change onthefly the q.concurrency (of var q=async.queue(... ) ) there is no change happening.

are there any other workarounds?

thanks

[aearly]

Is this related to #512 ? As far as I know, there's no clean way to change the concurrency on the fly.

[fprivitera]

no,
it is different : If I create a queue q with concurrency 5 and later I
change to q.concurrency=10, q.running() is still <=5.

On Sat, Apr 18, 2015 at 9:23 PM, Alexander Early notifications@github.com
wrote:

Is this related to #512 #512 ? As
far as I know, there's no clean way to change the concurrency on the fly.

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Reply to this email directly or view it on GitHub
#747 (comment).

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[fprivitera]

why we don't add a function on async.queue like this?

setConcurrency: function(c) {
        q.concurrency=c
        if (!q.paused && workers < q.concurrency && q.tasks.length) {
                var end=q.concurrency-workers
                    for (var i =0;i<end;i++) {
                        q.process()
                    }
                }
            }

[justincy]

@fprivitera is half right. The concurrency is only updated when new items are pushed onto the queue. That behavior can be fixed without adding the proposed setConcurrency function.

[justincy]

The concurrency is only updated when new items are pushed onto the queue.

I need to revise that statement to say "The concurrency can only be updated on the same event loop in which an item was added to the queue. And it can only be decreased, not increased."

I just added a failing test case. There was previously a test case for changing concurrency but it didn't correctly test situations where the concurrency can't be changed.

[aearly]

I think @justincy 's fix is good enough for now. If you want the queue to immediately take into account the new concurrency, you can manually call q.pause(); q.resume() to add more workers after settings the concurrency..