[PATCH master 3/5] Factor out instance existence checks

['Hrvoje Ribicic' via ganeti-devel]

These checks were repeated in the code, and will have to be reused for
the instance renames.

Signed-off-by: Hrvoje Ribicic <r...@google.com>
---
 lib/cmdlib/instance.py       | 14 ++++----------
 lib/cmdlib/instance_utils.py | 15 +++++++++++++++
 2 files changed, 19 insertions(+), 10 deletions(-)

diff --git a/lib/cmdlib/instance.py b/lib/cmdlib/instance.py
index 1a6d08b..a9d2843 100644
--- a/lib/cmdlib/instance.py
+++ b/lib/cmdlib/instance.py
@@ -65,7 +65,7 @@ from ganeti.cmdlib.instance_utils import 
BuildInstanceHookEnvByObject, \
   ReleaseLocks, CheckNodeVmCapable, CheckTargetNodeIPolicy, \
   GetInstanceInfoText, RemoveDisks, CheckNodeFreeMemory, \
   CheckInstanceBridgesExist, CheckNicsBridgesExist, UpdateMetadata, \
-  CheckCompressionTool
+  CheckCompressionTool, CheckInstanceExistence
 import ganeti.masterd.instance
 
 
@@ -578,10 +578,7 @@ class LUInstanceCreate(LogicalUnit):
 
     # this is just a preventive check, but someone might still add this
     # instance in the meantime, and creation will fail at lock-add time
-    if self.op.instance_name in\
-      [inst.name for inst in self.cfg.GetAllInstancesInfo().values()]:
-      raise errors.OpPrereqError("Instance '%s' is already in the cluster" %
-                                 self.op.instance_name, errors.ECODE_EXISTS)
+    CheckInstanceExistence(self, self.op.instance_name)
 
     self.add_locks[locking.LEVEL_INSTANCE] = self.op.instance_name
 
@@ -1900,11 +1897,8 @@ class LUInstanceRename(LogicalUnit):
                                    (hostname.ip, new_name),
                                    errors.ECODE_NOTUNIQUE)
 
-    instance_names = [inst.name for
-                      inst in self.cfg.GetAllInstancesInfo().values()]
-    if new_name in instance_names and new_name != instance.name:
-      raise errors.OpPrereqError("Instance '%s' is already in the cluster" %
-                                 new_name, errors.ECODE_EXISTS)
+    if new_name != instance.name:
+      CheckInstanceExistence(self, new_name)
 
   def Exec(self, feedback_fn):
     """Rename the instance.
diff --git a/lib/cmdlib/instance_utils.py b/lib/cmdlib/instance_utils.py
index 6674a76..f9545d0 100644
--- a/lib/cmdlib/instance_utils.py
+++ b/lib/cmdlib/instance_utils.py
@@ -744,3 +744,18 @@ def BuildDiskEnv(idx, disk):
   ret["INSTANCE_DISK%d_MODE" % idx] = mode
 
   return ret
+
+
+def CheckInstanceExistence(lu, instance_name):
+  """Raises an error if an instance with the given name exists already.
+
+  @type instance_name: string
+  @param instance_name: The name of the instance.
+
+  To be used in the locking phase.
+
+  """
+  if instance_name in \
+     [inst.name for inst in lu.cfg.GetAllInstancesInfo().values()]:
+    raise errors.OpPrereqError("Instance '%s' is already in the cluster" %
+                               instance_name, errors.ECODE_EXISTS)
-- 
2.0.0.526.g5318336