Problem is caused by the incorrect assumption the EC2Computer.getNode() will always return non-null. In fact this can return null if the actual instance has gone away (see the comments in Computer). But even if these were fixed, there are assumptions in the EC2 code that the EC2Computer.describeInstance() will be non-null, when this may not be the case. Need to go through all of this and make sure it's right.

Jan 25, 2012 10:38:56 PM hudson.slaves.NodeProvisioner update
WARNING: Provisioned slave Test AMI (ami-47e8b602) failed to launch
java.util.concurrent.ExecutionException: java.lang.NullPointerException
at java.util.concurrent.FutureTask$Sync.innerGet(FutureTask.java:222)
at java.util.concurrent.FutureTask.get(FutureTask.java:83)
at hudson.plugins.ec2.EC2Cloud$1.call(EC2Cloud.java:229)
at hudson.plugins.ec2.EC2Cloud$1.call(EC2Cloud.java:215)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
at java.util.concurrent.FutureTask.run(FutureTask.java:138)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:662)
Caused by: java.lang.NullPointerException
at hudson.plugins.ec2.EC2Computer._describeInstance(EC2Computer.java:98)
at hudson.plugins.ec2.EC2Computer.updateInstanceDescription(EC2Computer.java:68)
at hudson.plugins.ec2.ssh.EC2UnixLauncher.connectToSsh(EC2UnixLauncher.java:174)
at hudson.plugins.ec2.ssh.EC2UnixLauncher.launch(EC2UnixLauncher.java:53)
at hudson.plugins.ec2.EC2ComputerLauncher.launch(EC2ComputerLauncher.java:42)
at hudson.slaves.SlaveComputer$1.call(SlaveComputer.java:194)
... 5 more