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Can anyone explain why when I launch a new T2.micro instance, it occasionally (perhaps 1 in 50) starts with a CPU credit balance of zero, instead of the 30 it is meant to have?

I've attached screenshots of the CPU credit balances from two machines I launched nearly simultaneously from an Autoscaling group.

Normal startup - 30 credits initially

Abnormal startup - 0 credits

It isn't a massive deal, but it is upsetting my monitoring system to see near-zero cpu credits!

  • 1
    Are you starting many T2 instances during the same 24h period? docs.aws.amazon.com/AWSEC2/latest/UserGuide/… – Håkan Lindqvist Dec 3 '15 at 10:45
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    Spot on, I'd never noticed that footnote before! We launch ~6 instances every time someone pushes a code change, so we can easily exceed 100 in a busy day. Post as an answer and the kudos is all yours ;-) – Ian Bamforth Dec 3 '15 at 11:13
18

Amazon notes in their documentation on T2 (burstable) instances that while these instances normally have 30 CPU credits initially, there are limits to how this initial credit will be applied.

  • There are limits to how many T2 instances will launch or start with the initial CPU credit, which by default is set to 100 launches or starts of any T2 instance per account, per 24-hour period, per region. If you'd like to increase this limit, you can file a customer support limit increase request by using the Amazon EC2 Instance Request Form. If your account does not launch or start more than 100 T2 instances in 24 hours, this limit will not affect you.
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  • Yes that's the issue I also ran into. It's a ridiculous setting, it means you pay the full price and receive a tiny fraction of the usual worth. – John Nov 22 '17 at 1:05
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    @John Like the documentation states, you can file a ticket to get the limit raised. I would assume the limit exists to discourage people from large-scale automating using T2 instances for their initial CPU credit only. – Håkan Lindqvist Nov 22 '17 at 7:14

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