Check that instance exists before confirm. queries

Currently we ask the user for confirmation, and only after (try to)
remove, failover or migrate the instance. This doesn't work nicely if
the instance doesn't exist, so we make a query for the instance before
the prompt, which will throw an error in case it doesn't exist.

Side-note: the way the query works today is not really nice. It would be
better if we could query explicitly for a missing instance name, so that
this is done cleaner (explicit check) instead of side-effect (throw
exception). We do add code for this explicit check, except that today it
won't be used actually.

Reviewed-by: ultrotter

diff --git a/scripts/gnt-instance b/scripts/gnt-instance
index 9aa3e5f..57091e6 100755 (executable)
--- a/scripts/gnt-instance
+++ b/scripts/gnt-instance
@@ -176,6 +176,27 @@ def _TransformPath(user_input):
   return result_path
 
 
+def _EnsureInstancesExist(client, names):
+  """Check for and ensure the given instance names exist.
+
+  This function will raise an OpPrereqError in case they don't
+  exist. Otherwise it will exit cleanly.
+
+  @type client: L{luxi.Client}
+  @param client: the client to use for the query
+  @type names: list
+  @param names: the list of instance names to query
+  @raise errors.OpPrereqError: in case any instance is missing
+
+  """
+  # TODO: change LUQueryInstances to that it actually returns None
+  # instead of raising an exception, or devise a better mechanism
+  result = client.QueryInstances(names, ["name"])
+  for orig_name, row in zip(names, result):
+    if row[0] is None:
+      raise errors.OpPrereqError("Instance '%s' does not exist" % orig_name)
+
+
 def ListInstances(opts, args):
   """List instances and their properties.
 
@@ -559,8 +580,11 @@ def RemoveInstance(opts, args):
   """
   instance_name = args[0]
   force = opts.force
+  cl = GetClient()
 
   if not force:
+    _EnsureInstancesExist(cl, [instance_name])
+
     usertext = ("This will remove the volumes of the instance %s"
                 " (including mirrors), thus removing all the data"
                 " of the instance. Continue?") % instance_name
@@ -569,7 +593,7 @@ def RemoveInstance(opts, args):
 
   op = opcodes.OpRemoveInstance(instance_name=instance_name,
                                 ignore_failures=opts.ignore_failures)
-  SubmitOrSend(op, opts)
+  SubmitOrSend(op, opts, cl=cl)
   return 0
 
 
@@ -811,10 +835,13 @@ def FailoverInstance(opts, args):
   @return: the desired exit code
 
   """
+  cl = GetClient()
   instance_name = args[0]
   force = opts.force
 
   if not force:
+    _EnsureInstancesExist(cl, [instance_name])
+
     usertext = ("Failover will happen to image %s."
                 " This requires a shutdown of the instance. Continue?" %
                 (instance_name,))
@@ -823,7 +850,7 @@ def FailoverInstance(opts, args):
 
   op = opcodes.OpFailoverInstance(instance_name=instance_name,
                                   ignore_consistency=opts.ignore_consistency)
-  SubmitOrSend(op, opts)
+  SubmitOrSend(op, opts, cl=cl)
   return 0
 
 
@@ -839,10 +866,13 @@ def MigrateInstance(opts, args):
   @return: the desired exit code
 
   """
+  cl = GetClient()
   instance_name = args[0]
   force = opts.force
 
   if not force:
+    _EnsureInstancesExist(cl, [instance_name])
+
     if opts.cleanup:
       usertext = ("Instance %s will be recovered from a failed migration."
                   " Note that the migration procedure (including cleanup)" %
@@ -858,7 +888,7 @@ def MigrateInstance(opts, args):
 
   op = opcodes.OpMigrateInstance(instance_name=instance_name, live=opts.live,
                                  cleanup=opts.cleanup)
-  SubmitOpCode(op)
+  SubmitOpCode(op, cl=cl)
   return 0