For the autoscaling lab, the package "stress" seems to now require the EPEL repo if you are using Amazon Linux 2. I changed the userdata script as follows:
yum update -y
sudo yum install -y /tmp/epel-release-latest-7.noarch.rpm
yum install -y stress
/usr/bin/stress –cpu 8 –timeout 10m
Ahhh, yes. Thanks Dave! Just pushed an update.