Convert LUConnectConsole to concurrency

For ConnectConsole we just need to lock the instance we're connecting
to. We make a few rpcs to its primary node, but node daemons can now
handle multiple queries and nodes cannot be removed till they have
instances on them anyway. Note that since we return the ssh command, and
that's executed outside of the ganeti daemon, without any locks held,
the instance can then be subject to operations while we're connected to
it, but that was the previous behavior as well.

Reviewed-by: iustinp

diff --git a/lib/cmdlib.py b/lib/cmdlib.py
index 2fecf32..ca7ff68 100644 (file)
--- a/lib/cmdlib.py
+++ b/lib/cmdlib.py
@@ -3354,6 +3354,10 @@ class LUConnectConsole(NoHooksLU):
 
   """
   _OP_REQP = ["instance_name"]
+  REQ_BGL = False
+
+  def ExpandNames(self):
+    self._ExpandAndLockInstance()
 
   def CheckPrereq(self):
     """Check prerequisites.
@@ -3361,12 +3365,9 @@ class LUConnectConsole(NoHooksLU):
     This checks that the instance is in the cluster.
 
     """
-    instance = self.cfg.GetInstanceInfo(
-      self.cfg.ExpandInstanceName(self.op.instance_name))
-    if instance is None:
-      raise errors.OpPrereqError("Instance '%s' not known" %
-                                 self.op.instance_name)
-    self.instance = instance
+    self.instance = self.cfg.GetInstanceInfo(self.op.instance_name)
+    assert self.instance is not None, \
+      "Cannot retrieve locked instance %s" % self.op.instance_name
 
   def Exec(self, feedback_fn):
     """Connect to the console of an instance