An instance in a fleet was interrupted although it was in full protection

Hello

Is it possible to interrupt an instance on Spot in a fleet although it was in full protection?

In short yes.

“Spot Instances can be interrupted with two minutes’ notification when AWS needs the capacity back” - https://docs.aws.amazon.com/gamelift/latest/developerguide/spot-tasks.html

Thats the trade-off with Spot. You are getting the EC2 spare capacity in a region at very reduced price. As that spare capacity is consumed then EC2 begins to take back the spot instances.

There is nothing that GameLift can do to prevent this as EC2 is terminating the instance here and not GameLift. GameLift has some advice about using spot effectively here : https://docs.aws.amazon.com/gamelift/latest/developerguide/queues-design.html#queues-design-spot

You can mitigate some of this by tracking metrics about instance types and interruption rates (see the GameLift fleet metrics around InstanceInterruptions and GameSessionInterruptions) and being flexible on spot types. FleetIQ attempts to shield you from spot interruptions by tracking interruption rate across instance types and region and intelligently placing sessions either on your on demand or spot fleets.

The ideal workaround for games that want to use spot but have shorter session times is to be able to use spot blocks: https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/spot-requests.html#fixed-duration-spot-instances. However GameLift does not support this feature and EC2 only has very fixed spot block times at this moment. Also spot blocks cost more than just spot on its own.

Hope thats useful.