The roller script takes a AMI name as a parameter and performs a rolling
update on the selected auto scaling group.
First the auto scaling group will be updated to use the new AMI and its
MinSize, MaxSize and DesiredCapacity values are increase by 1. Once
scaled out, roller terminates the remaining instances with the old launch
configuration and waits that a new instance with the new launch configruation
gets ready. This step will be repeated till all old instances are terminated.
Finally the auto scaling capacity will be set to its original state.
npm install -g a-rollerroller --region aws-region --group "Auto scaling group name" --ami "AMI name"