The ec2-plugin will treat a still-launching node as idle (because it has no jbs running) and will thus shut it down if its idle timeout expires.

This means that if the idle timeout for a node is shorter than the time it takes to do one-off configuration on first launch, it will be shut down before it finishes starting up, aborting any init script that might be in progress.

That's a clear bug - a node isn't idle when it's launching, and shouldn't be idled out until it's first made a connection with its slave agent.