EC2 Instance Hibernating when it shouldnt be able to.

Question

Hi, I've seen some behaviour I dont understand and am wondering if can be explained please.

**EC2 Windows instance.  **
* EBS not encrypted. 
* Stop-hibernate behavior - Disabled.

Instance stopped on 18th.  Restarted on 20th.
Triggering of Lambda based upon CloudWatch Logs receiving a 6005 event from Windows system log fails to launch.

Investigation shows that there was no such event as the instance didnt actually start from cold.  What is seen is the following:

*The system has returned from a low power state.

Sleep Time: ‎2023‎-‎01‎-‎18T20:46:45.052207200Z
Wake Time: ‎2023‎-‎01‎-‎20T11:16:45.233015100Z

Wake Source: Unknown*

So the instance was hibernated?  How?  What am I missing?

It's not an issue as I've used the EventBridge to pickup on 'EC2 Instance State-change Notification' now which is much nicer, but I'm still curious as to what happened.

Cheers

Answer

Try checking the Stop-hibernate behavior settings of your ec2 instance; it may be going into hibernate when stopped. Another reason could be that windows instances have their inbuilt power management feature which we can configure to hibernate the machine after a specific amount of time. You can also check this and the windows system logs. Also from the event bridge configure the cloudwatch rule, for instance, state change so that you will get notified of these events.

EC2 Instance Hibernating when it shouldnt be able to.

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