I would like to be able to have instances from one of my ec2 clusters to talk to instances in another ec2 cluster in real time (not via a rdbms or messaging queue).
I'm thinking the best way to do this is with SSH (communications so far are only one way), as this communication doesn't occur very often, and it doesnt make sense to have something always open listening for requests (like a webserver, or some other specialized socket app).
1) Is there a better way of doing this than using SSH?
2) Is there a way of using amazon or plain old SSH to easily restrict SSH logins based on security group? I don't want to have to worry about creating a dynamically changing IP white list, or managing a bunch of random passwords, or storing different pem files in my DVCS. What I'd ideally like is one password or pem that is used for interinstance communication across all environments, and then set firewall rules that prevent SSH access for any machine that is not in the designated security group.