I have recently been spinning up a lot of t1.micro instances on Amazon's EC2 service. I'm deliberately using minimal / default images, and I need to install Java on them from scratch. There have been reports (and I have experienced myself) that the Java install process hangs indefinitely when installing either Oracle's JRE/JDK or OpenJDK on a t1.micro running Ubuntu. I have been able to install Java successfully by explicitly requiring a 64-bit version of the OS.
Here's how you can do that in your Pallet node-spec: