Azure Function Queue Trigger sometimes doesn't scale and one instance processing all queue messages

Question

I have Azure Functions v1 (Consumption plan) triggered with queue. Function take message from queue, get blob (blob url is in queue), make Http request and that's all.

We depends on that functions automatically scales when necessary so queue is ideally empty. Everything works just fine, multiple instances processing queue and then all of sudden all instances (except one) stop working and only one is left and processing queue (which takes about 7 hours).

On picture below is with red line marked that. Before and after everything scale just right.

Do you have any idea how this is possible, what happened with scaling?

@RohitSaigal sorry I should mention that - it is consumption plan. — Adam Lihm
– Adam Lihm, Commented Mar 11, 2019 at 14:56
Can you check and confirm that there is no errors in the function execution from the logs ? — Ketan
– Ketan, Commented Mar 15, 2019 at 15:50
1up for the fact we experience the same thing. No mentions anywhere else of this problem and support saying this is an issue on their side but no in depth details of what it is or how they're tackling it. Stopping and starting does sometimes work. We also have to redeploy (delete the service and start again) sometimes to kick the scaling back in. Just nice to know we're not alone — no1spirite
– no1spirite, Commented Oct 8, 2019 at 8:09
@no1spirite Well it is quite sad from Azure Functions team, that they still didn't figure this out. We didn't experience this issue anymore, after they confirmed us, that is their problem. But we have another issue that scaling up takes so long, we have to change technology and now Azure Queue is processed inside Worker Role, where we have full control about scaling and so far so good. — Adam Lihm
– Adam Lihm, Commented Oct 8, 2019 at 19:31

Adam Lihm · Accepted Answer · 2019-03-31 21:52:28Z

1

So after communication with support they confirmed that problem was on their side. But if you experience similar trouble stop and start functions help (not restart).

answered Mar 31, 2019 at 21:52

Adam Lihm

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