Centralize the creation of a WConfd context in Python code

This will allow easier modification of the structure of a client
identity later.

Also add a helper method for creating a WConfd context from a context.
Signed-off-by: Petr Pudlak <pudlak@google.com>
Reviewed-by: Klaus Aehlig <aehlig@google.com>

lib/config.py

@@ -39,6 +39,7 @@ import os
 import random
 import logging
 import time
+import threading
 import itertools
 
 from ganeti import errors
@@ -62,6 +63,25 @@ _config_lock = locking.SharedLock("ConfigWriter")
 _UPGRADE_CONFIG_JID = "jid-cfg-upgrade"
 
 
+def GetWConfdContext(ec_id, livelock):
+  """Prepare a context for communication with WConfd.
+
+  WConfd needs to know the identity of each caller to properly manage locks and
+  detect job death. This helper function prepares the identity object given a
+  job ID (optional) and a livelock file.
+
+  @type ec_id: int, or None
+  @param ec_id: the job ID or None, if the caller isn't a job
+  @type livelock: L{ganeti.utils.livelock.LiveLock}
+  @param livelock: a livelock object holding the lockfile needed for WConfd
+  @return: the WConfd context
+
+  """
+  return (ec_id,
+          threading.current_thread().ident,
+          livelock.lockfile.name)
+
+
 def _ValidateConfig(data):
   """Verifies that a configuration objects looks valid.
 

lib/mcpu.py

@@ -33,7 +33,6 @@ import logging
 import random
 import time
 import itertools
-import threading
 import traceback
 
 from ganeti import opcodes
@@ -309,9 +308,8 @@ class Processor(object):
     self.hmclass = hooksmaster.HooksMaster
     self._enable_locks = enable_locks
     self.wconfd = wconfd # Indirection to allow testing
-    self._wconfdcontext = (ec_id,
-                           threading.current_thread().ident,
-                           self.context.livelock.lockfile.name)
+    self._wconfdcontext = context.GetWConfdContext(ec_id)
+
 
   def _CheckLocksEnabled(self):
     """Checks if locking is enabled.

lib/server/masterd.py

@@ -488,6 +488,9 @@ class GanetiContext(object):
     assert self.__class__._instance is None, "Attempt to modify Ganeti Context"
     object.__setattr__(self, name, value)
 
+  def GetWConfdContext(self, ec_id):
+    return config.GetWConfdContext(ec_id, self.livelock)
+
   def AddNode(self, node, ec_id):
     """Adds a node to the configuration.