Listing of instances to be terminated before the prompt

Will list the EC2 instances before detroying the cluster.
This was added because it can be scary to destroy EC2
instances without knowing which one will be impacted.

Author: Jean-Martin Archer

ec2/spark_ec2.py

@@ -223,7 +223,7 @@ def launch_cluster(conn, opts, cluster_name):
     sys.exit(1)
   if opts.key_pair is None:
     print >> stderr, "ERROR: Must provide a key pair name (-k) to use on instances."
-    sys.exit(1)    
+    sys.exit(1)
   print "Setting up security groups..."
   master_group = get_or_make_group(conn, cluster_name + "-master")
   slave_group = get_or_make_group(conn, cluster_name + "-slaves")
@@ -691,12 +691,18 @@ def real_main():
     setup_cluster(conn, master_nodes, slave_nodes, opts, True)
 
   elif action == "destroy":
-    response = raw_input("Are you sure you want to destroy the cluster " +
-        cluster_name + "?\nALL DATA ON ALL NODES WILL BE LOST!!\n" +
+    (master_nodes, slave_nodes) = get_existing_cluster(
+        conn, opts, cluster_name, die_on_error=False)
+
+    print "Are you sure you want to destroy the cluster " + \
+      cluster_name + "?\nThe following instances will be terminated:"
+    for inst in master_nodes + slave_nodes:
+      print inst
+
+    response = raw_input("ALL DATA ON ALL NODES WILL BE LOST!!\n" +
         "Destroy cluster " + cluster_name + " (y/N): ")
+
     if response == "y":
-      (master_nodes, slave_nodes) = get_existing_cluster(
-          conn, opts, cluster_name, die_on_error=False)
       print "Terminating master..."
       for inst in master_nodes:
         inst.terminate()