diff --git a/INSTALL b/INSTALL
index e33ab96..95f3019 100644
--- a/INSTALL
+++ b/INSTALL
@@ -42,7 +42,9 @@
 - `Paramiko <http://www.lag.net/paramiko/>`_, if you want to use
   ``ganeti-listrunner``
 - `psutil Python module <https://github.com/giampaolo/psutil>`_,
-  optional python package for supporting CPU pinning under KVM
+  optional python package for supporting CPU pinning under KVM, versions
+  2.x.x only; beware that versions from 2.0.0 to before 2.2.0 had a
+  number of file handle leaks, so running at least 2.2.0 is advised
 - `fdsend Python module <https://gitorious.org/python-fdsend>`_,
   optional Python package for supporting NIC hotplugging under KVM
 - `qemu-img <http://qemu.org/>`_, if you want to use ``ovfconverter``
diff --git a/lib/backend.py b/lib/backend.py
index 9ea1c50..e597410 100644
--- a/lib/backend.py
+++ b/lib/backend.py
@@ -1104,6 +1104,7 @@
 
   return result
 
+
 def VerifyNodeNetTest(my_name, test_config):
   """Verify nodes are reachable.
 
@@ -1146,6 +1147,7 @@
                         " and ".join(fail))
   return result
 
+
 def VerifyMasterIP(my_name, test_config):
   """Verify master IP is reachable.
 
diff --git a/lib/cli.py b/lib/cli.py
index 0139a24..1a1815c 100644
--- a/lib/cli.py
+++ b/lib/cli.py
@@ -747,7 +747,7 @@
         timer += constants.CLI_WFJC_FREQUENCY
     else:
       result = cbs.WaitForJobChangeOnce(job_id, ["status"], prev_job_info,
-                                      prev_logmsg_serial, timeout=update_freq)
+                                        prev_logmsg_serial, timeout=update_freq)
     if not result:
       # job not found, go away!
       raise errors.JobLost("Job with id %s lost" % job_id)
@@ -906,6 +906,7 @@
     """
     return self.cl.CancelJob(job_id)
 
+
 class FeedbackFnJobPollReportCb(JobPollReportCbBase):
   def __init__(self, feedback_fn):
     """Initializes this class.
diff --git a/lib/cmdlib/cluster/verify.py b/lib/cmdlib/cluster/verify.py
index ef286c1..76809b6 100644
--- a/lib/cmdlib/cluster/verify.py
+++ b/lib/cmdlib/cluster/verify.py
@@ -109,8 +109,8 @@
     @type error_descriptor: tuple (string, string, string)
     @param error_descriptor: triplet describing the error (object_type,
         code, description)
-    @type obj_name: string
-    @param obj_name: name of object (instance, node ..) the error relates to
+    @type object_name: string
+    @param object_name: name of object (instance, node ..) the error relates to
     @type message_list: list of strings
     @param message_list: body of error messages
     @type log_type: string
@@ -133,13 +133,15 @@
             log_type, error_code, object_type, object_name, msg))
     else:
       if not object_name:
-        object_name  = ""
+        object_name = ""
       for msg in message_list:
         prefixed_list.append("  - %s: %s %s: %s" % (
             log_type, object_type, object_name, msg))
 
     # Report messages via the feedback_fn
-    self._feedback_fn(constants.ELOG_MESSAGE_LIST, prefixed_list) # pylint: disable=E1101,C0301
+    # pylint: disable=E1101
+    self._feedback_fn(constants.ELOG_MESSAGE_LIST, prefixed_list)
+    # pylint: enable=E1101
 
     # do not mark the operation as failed for WARN cases only
     if log_type == self.ETYPE_ERROR:
@@ -781,8 +783,8 @@
 
     if constants.NV_MASTERIP not in nresult:
       self._ErrorMsg(constants.CV_ENODENET, ninfo.name,
-                    "node hasn't returned node master IP reachability data")
-    elif nresult[constants.NV_MASTERIP] == False: # be explicit, could be None
+                     "node hasn't returned node master IP reachability data")
+    elif nresult[constants.NV_MASTERIP] == False:  # be explicit, could be None
       if ninfo.uuid == self.master_node:
         msg = "the master node cannot reach the master IP (not configured?)"
       else:
diff --git a/lib/http/server.py b/lib/http/server.py
index 8b3a4ee..9a4563e 100644
--- a/lib/http/server.py
+++ b/lib/http/server.py
@@ -423,7 +423,8 @@
           try:
             http.Handshake(sock, self.WRITE_TIMEOUT)
           except http.HttpSessionHandshakeUnexpectedEOF:
-            logging.debug("Unexpected EOF from %s:%s" % (client_addr[0], client_addr[1]))
+            logging.debug("Unexpected EOF from %s:%s",
+                          client_addr[0], client_addr[1])
             # Ignore rest
             return
 
@@ -609,8 +610,9 @@
         t_setup = time.time()
         self.request_executor(self, self.handler, connection, client_addr)
         t_end = time.time()
-        logging.debug("Request from %s:%s executed in: %.4f [setup: %.4f] [workers: %d]" % (
-            client_addr[0], client_addr[1], t_end - t_start, t_setup - t_start, len(self._children)))
+        logging.debug("Request from %s:%s executed in: %.4f [setup: %.4f] "
+                      "[workers: %d]", client_addr[0], client_addr[1],
+                      t_end - t_start, t_setup - t_start, len(self._children))
 
       except Exception: # pylint: disable=W0703
         logging.exception("Error while handling request from %s:%s",
diff --git a/lib/hypervisor/hv_kvm/__init__.py b/lib/hypervisor/hv_kvm/__init__.py
index 1e89c82..580606b 100644
--- a/lib/hypervisor/hv_kvm/__init__.py
+++ b/lib/hypervisor/hv_kvm/__init__.py
@@ -45,7 +45,17 @@
 from bitarray import bitarray
 try:
   import psutil   # pylint: disable=F0401
+  if psutil.version_info < (2, 0, 0):
+    # The psutil version seems too old, we ignore it
+    psutil_err = "too old (2.x.x needed, %s found)" % psutil.__version__
+    psutil = None
+  elif psutil.version_info >= (3,):
+    psutil_err = "too new (2.x.x needed, %s found)" % psutil.__version__
+    psutil = None
+  else:
+    psutil_err = "<no error>"
 except ImportError:
+  psutil_err = "not found"
   psutil = None
 try:
   import fdsend   # pylint: disable=F0401
@@ -885,11 +895,14 @@
 
     """
     if psutil is None:
-      raise errors.HypervisorError("psutil Python package not"
-                                   " found; cannot use CPU pinning under KVM")
+      raise errors.HypervisorError("psutil Python package %s"
+                                   "; cannot use CPU pinning"
+                                   " under KVM" % psutil_err)
 
     target_process = psutil.Process(process_id)
     if cpus == constants.CPU_PINNING_OFF:
+      # we checked this at import time
+      # pylint: disable=E1101
       target_process.set_cpu_affinity(range(psutil.cpu_count()))
     else:
       target_process.set_cpu_affinity(cpus)
diff --git a/lib/rapi/rlib2.py b/lib/rapi/rlib2.py
index 751e6ef..8514fcb 100644
--- a/lib/rapi/rlib2.py
+++ b/lib/rapi/rlib2.py
@@ -200,6 +200,7 @@
 
   return inst
 
+
 def _CheckIfConnectionDropped(sock):
   """Utility function to monitor the state of an open connection.
 
diff --git a/lib/storage/bdev.py b/lib/storage/bdev.py
index 1f95004..7c1897c 100644
--- a/lib/storage/bdev.py
+++ b/lib/storage/bdev.py
@@ -510,7 +510,6 @@
       logging.warning("lvs command returned an empty output, the LV cache will"
                       "be empty!")
       return {}
-    info = {}
     return dict([LogicalVolume._ParseLvInfoLine(line, sep) for line in out])
 
   def Attach(self, lv_info=None):
diff --git a/src/Ganeti/Confd/Server.hs b/src/Ganeti/Confd/Server.hs
index 3ff0393..a2ec0a9 100644
--- a/src/Ganeti/Confd/Server.hs
+++ b/src/Ganeti/Confd/Server.hs
@@ -58,7 +58,7 @@
 import Ganeti.BasicTypes
 import Ganeti.Errors
 import Ganeti.Daemon
-import Ganeti.JSON
+import Ganeti.JSON (containerFromList, fromContainer)
 import Ganeti.Objects
 import Ganeti.Confd.Types
 import Ganeti.Confd.Utils
diff --git a/src/Ganeti/Confd/Utils.hs b/src/Ganeti/Confd/Utils.hs
index 4e43642..ba5585f 100644
--- a/src/Ganeti/Confd/Utils.hs
+++ b/src/Ganeti/Confd/Utils.hs
@@ -59,7 +59,7 @@
 import Ganeti.Hash
 import qualified Ganeti.Constants as C
 import qualified Ganeti.Path as Path
-import Ganeti.JSON
+import Ganeti.JSON (fromJResult)
 import Ganeti.Utils
 
 -- | Type-adjusted max clock skew constant.
diff --git a/src/Ganeti/Config.hs b/src/Ganeti/Config.hs
index f67aff1..5687b54 100644
--- a/src/Ganeti/Config.hs
+++ b/src/Ganeti/Config.hs
@@ -103,7 +103,7 @@
 import qualified Ganeti.Constants as C
 import qualified Ganeti.ConstantUtils as CU
 import Ganeti.Errors
-import Ganeti.JSON
+import Ganeti.JSON (fromJResult, fromContainer, GenericContainer(..))
 import Ganeti.Objects
 import Ganeti.Types
 import qualified Ganeti.Utils.MultiMap as MM
diff --git a/src/Ganeti/DataCollectors/Lv.hs b/src/Ganeti/DataCollectors/Lv.hs
index 4846988..27a80cc 100644
--- a/src/Ganeti/DataCollectors/Lv.hs
+++ b/src/Ganeti/DataCollectors/Lv.hs
@@ -61,7 +61,7 @@
 import Ganeti.Confd.ClientFunctions
 import Ganeti.DataCollectors.CLI
 import Ganeti.DataCollectors.Types
-import Ganeti.JSON
+import Ganeti.JSON (fromJResult)
 import Ganeti.Objects
 import Ganeti.Storage.Lvm.LVParser
 import Ganeti.Storage.Lvm.Types
diff --git a/src/Ganeti/HTools/Backend/IAlloc.hs b/src/Ganeti/HTools/Backend/IAlloc.hs
index e431947..e40c3d7 100644
--- a/src/Ganeti/HTools/Backend/IAlloc.hs
+++ b/src/Ganeti/HTools/Backend/IAlloc.hs
@@ -65,7 +65,7 @@
 import Ganeti.HTools.CLI
 import Ganeti.HTools.Loader
 import Ganeti.HTools.Types
-import Ganeti.JSON
+import Ganeti.JSON (maybeFromObj, JSRecord, tryFromObj, toArray, asObjectList, readEitherString, fromJResult, fromObj, fromObjWithDefault, asJSObject, emptyContainer)
 import Ganeti.Types ( EvacMode(ChangePrimary, ChangeSecondary)
                     , adminStateFromRaw, AdminState(..))
 import Ganeti.Utils
diff --git a/src/Ganeti/HTools/Backend/Luxi.hs b/src/Ganeti/HTools/Backend/Luxi.hs
index be81a3c..639d74d 100644
--- a/src/Ganeti/HTools/Backend/Luxi.hs
+++ b/src/Ganeti/HTools/Backend/Luxi.hs
@@ -51,8 +51,9 @@
 import qualified Ganeti.HTools.Group as Group
 import qualified Ganeti.HTools.Node as Node
 import qualified Ganeti.HTools.Instance as Instance
-import Ganeti.JSON
-import Ganeti.Objects as O
+import Ganeti.JSON (fromJVal, tryFromObj, arrayMaybeFromJVal,
+                    getKeysFromContainer, Container)
+import Ganeti.Objects (PartialNicParams)
 
 {-# ANN module "HLint: ignore Eta reduce" #-}
 
diff --git a/src/Ganeti/HTools/Backend/MonD.hs b/src/Ganeti/HTools/Backend/MonD.hs
index d7d8b4c..be420a5 100644
--- a/src/Ganeti/HTools/Backend/MonD.hs
+++ b/src/Ganeti/HTools/Backend/MonD.hs
@@ -78,7 +78,7 @@
 import Ganeti.HTools.Loader (ClusterData(..))
 import Ganeti.HTools.Types
 import Ganeti.HTools.CLI
-import Ganeti.JSON
+import Ganeti.JSON (fromJVal, tryFromObj, JSRecord, loadJSArray, maybeParseMap)
 import Ganeti.Logging.Lifted (logWarning)
 import Ganeti.Utils (exitIfBad)
 
diff --git a/src/Ganeti/HTools/Backend/Rapi.hs b/src/Ganeti/HTools/Backend/Rapi.hs
index 03d158c..218411c 100644
--- a/src/Ganeti/HTools/Backend/Rapi.hs
+++ b/src/Ganeti/HTools/Backend/Rapi.hs
@@ -53,7 +53,7 @@
 import Ganeti.BasicTypes
 import Ganeti.HTools.Loader
 import Ganeti.HTools.Types
-import Ganeti.JSON
+import Ganeti.JSON (loadJSArray, JSRecord, tryFromObj, fromJVal, maybeFromObj, fromJResult, tryArrayMaybeFromObj, readEitherString, fromObjWithDefault, asJSObject, emptyContainer)
 import qualified Ganeti.HTools.Group as Group
 import qualified Ganeti.HTools.Node as Node
 import qualified Ganeti.HTools.Instance as Instance
diff --git a/src/Ganeti/JQScheduler/Filtering.hs b/src/Ganeti/JQScheduler/Filtering.hs
index 34e55bb..c031415 100644
--- a/src/Ganeti/JQScheduler/Filtering.hs
+++ b/src/Ganeti/JQScheduler/Filtering.hs
@@ -56,7 +56,7 @@
 import Ganeti.JQScheduler.Types
 import Ganeti.JQueue (QueuedJob(..))
 import Ganeti.JQueue.Lens
-import Ganeti.JSON
+import Ganeti.JSON (nestedAccessByKeyDotted)
 import Ganeti.Objects (FilterRule(..), FilterAction(..), FilterPredicate(..),
                        filterRuleOrder)
 import Ganeti.OpCodes (OpCode)
diff --git a/src/Ganeti/JQueue.hs b/src/Ganeti/JQueue.hs
index a3f9da2..736fce6 100644
--- a/src/Ganeti/JQueue.hs
+++ b/src/Ganeti/JQueue.hs
@@ -122,7 +122,7 @@
 import Ganeti.Errors (ErrorResult, ResultG)
 import Ganeti.JQueue.Lens (qoInputL, validOpCodeL)
 import Ganeti.JQueue.Objects
-import Ganeti.JSON
+import Ganeti.JSON (fromJResult, fromObjWithDefault)
 import Ganeti.Logging
 import Ganeti.Luxi
 import Ganeti.Objects (ConfigData, Node)
diff --git a/src/Ganeti/JSON.hs b/src/Ganeti/JSON.hs
index a666ba2..86323ba 100644
--- a/src/Ganeti/JSON.hs
+++ b/src/Ganeti/JSON.hs
@@ -549,4 +549,4 @@
 
 -- | Maybe obtain a map from a JSON object.
 maybeParseMap :: J.JSON a => J.JSValue -> Maybe (Map.Map String a)
-maybeParseMap = liftM fromContainer . readContainer <=< asJSObject
+maybeParseMap =liftM fromContainer . readContainer <=< asJSObject
diff --git a/src/Ganeti/Luxi.hs b/src/Ganeti/Luxi.hs
index 4439cef..831e859 100644
--- a/src/Ganeti/Luxi.hs
+++ b/src/Ganeti/Luxi.hs
@@ -73,7 +73,7 @@
 import Ganeti.BasicTypes
 import Ganeti.Constants
 import Ganeti.Errors
-import Ganeti.JSON
+import Ganeti.JSON (fromJResult, fromJVal, fromObj, Tuple5(..), MaybeForJSON(..), TimeAsDoubleJSON(..))
 import Ganeti.UDSServer
 import Ganeti.Objects
 import Ganeti.OpParams (pTagsObject)
diff --git a/src/Ganeti/Objects.hs b/src/Ganeti/Objects.hs
index 4b92561..065aaa8 100644
--- a/src/Ganeti/Objects.hs
+++ b/src/Ganeti/Objects.hs
@@ -130,7 +130,7 @@
 import qualified AutoConf
 import qualified Ganeti.Constants as C
 import qualified Ganeti.ConstantUtils as ConstantUtils
-import Ganeti.JSON
+import Ganeti.JSON (DictObject(..), Container, emptyContainer, GenericContainer)
 import Ganeti.Objects.BitArray (BitArray)
 import Ganeti.Objects.Disk
 import Ganeti.Objects.Maintenance
diff --git a/src/Ganeti/Objects/BitArray.hs b/src/Ganeti/Objects/BitArray.hs
index f121ba4..62b45c4 100644
--- a/src/Ganeti/Objects/BitArray.hs
+++ b/src/Ganeti/Objects/BitArray.hs
@@ -63,7 +63,7 @@
 import qualified Text.JSON as J
 
 import Ganeti.BasicTypes
-import Ganeti.JSON
+import Ganeti.JSON (readEitherString)
 
 -- | A fixed-size, space-efficient array of bits.
 data BitArray = BitArray
diff --git a/src/Ganeti/Objects/Disk.hs b/src/Ganeti/Objects/Disk.hs
index 4e95749..f6b3cbb 100644
--- a/src/Ganeti/Objects/Disk.hs
+++ b/src/Ganeti/Objects/Disk.hs
@@ -83,7 +83,7 @@
   showsPrec _ (LogicalVolume g v) =
     showString g . showString "/" . showString v
 
--- | Check the constraints for a VG/LV names (except the \@\/dev\/\@ check).
+-- | Check the constraints for VG\/LV names (except the @\/dev\/@ check).
 instance Validatable LogicalVolume where
   validate (LogicalVolume g v) = do
       let vgn = "Volume group name"
diff --git a/src/Ganeti/OpParams.hs b/src/Ganeti/OpParams.hs
index a965df3..83fd2c4 100644
--- a/src/Ganeti/OpParams.hs
+++ b/src/Ganeti/OpParams.hs
@@ -324,7 +324,7 @@
 import Ganeti.THH
 import Ganeti.THH.Field
 import Ganeti.Utils
-import Ganeti.JSON
+import Ganeti.JSON (GenericContainer)
 import Ganeti.Types
 import qualified Ganeti.Query.Language as Qlang
 
diff --git a/src/Ganeti/Query/Common.hs b/src/Ganeti/Query/Common.hs
index 6f8e126..31c40d6 100644
--- a/src/Ganeti/Query/Common.hs
+++ b/src/Ganeti/Query/Common.hs
@@ -67,7 +67,7 @@
 import qualified Ganeti.Constants as C
 import Ganeti.Config
 import Ganeti.Errors
-import Ganeti.JSON
+import Ganeti.JSON (GenericContainer(..), fromContainer, TimeAsDoubleJSON(..))
 import Ganeti.Objects
 import Ganeti.Rpc
 import Ganeti.Query.Language
diff --git a/src/Ganeti/Query/Filter.hs b/src/Ganeti/Query/Filter.hs
index cddc4d8..0d36ff2 100644
--- a/src/Ganeti/Query/Filter.hs
+++ b/src/Ganeti/Query/Filter.hs
@@ -84,7 +84,7 @@
 import Ganeti.Query.Language
 import Ganeti.Query.Types
 import Ganeti.Utils.Monad (anyM, allM)
-import Ganeti.JSON
+import Ganeti.JSON (fromJVal)
 
 -- | Compiles a filter based on field names to one based on getters.
 compileFilter :: FieldMap a b
diff --git a/src/Ganeti/Query/Instance.hs b/src/Ganeti/Query/Instance.hs
index 4d2e660..8ea2c0f 100644
--- a/src/Ganeti/Query/Instance.hs
+++ b/src/Ganeti/Query/Instance.hs
@@ -59,7 +59,7 @@
 import qualified Ganeti.Constants as C
 import qualified Ganeti.ConstantUtils as C
 import Ganeti.Errors
-import Ganeti.JSON
+import Ganeti.JSON (MaybeForJSON(..), fromContainer)
 import Ganeti.Objects
 import Ganeti.Query.Common
 import Ganeti.Query.Language
diff --git a/src/Ganeti/Query/Network.hs b/src/Ganeti/Query/Network.hs
index 1fda614..3ef0803 100644
--- a/src/Ganeti/Query/Network.hs
+++ b/src/Ganeti/Query/Network.hs
@@ -47,7 +47,7 @@
 import Data.Maybe (fromMaybe, mapMaybe)
 import Data.List (find, intercalate)
 
-import Ganeti.JSON
+import Ganeti.JSON (fromContainer)
 import Ganeti.Network
 import Ganeti.Objects
 import qualified Ganeti.Objects.BitArray as BA
diff --git a/src/Ganeti/Query/Node.hs b/src/Ganeti/Query/Node.hs
index 698e209..f431ade 100644
--- a/src/Ganeti/Query/Node.hs
+++ b/src/Ganeti/Query/Node.hs
@@ -43,13 +43,12 @@
 
 import Data.List (intercalate)
 import Data.Maybe
-import qualified Data.Map as Map
 import qualified Text.JSON as J
 
 import Ganeti.Config
 import Ganeti.Common
 import Ganeti.Objects
-import Ganeti.JSON
+import Ganeti.JSON (jsonHead)
 import Ganeti.Rpc
 import Ganeti.Types
 import Ganeti.Query.Language
@@ -306,10 +305,10 @@
   let hvs = [getDefaultHypervisorSpec cfg |
              queryDomainRequired hypervisorFields fields]
       good_nodes = nodesWithValidConfig cfg nodes
-      storage_units = if queryDomainRequired storageFields fields
-                        then getStorageUnitsOfNodes cfg good_nodes
-                        else Map.fromList
-                          (map (\n -> (uuidOf n, [])) good_nodes)
-  rpcres <- executeRpcCall good_nodes (RpcCallNodeInfo storage_units hvs)
+      storage_units n = if queryDomainRequired storageFields fields
+                        then getStorageUnitsOfNode cfg n
+                        else []
+  rpcres <- executeRpcCalls
+      [(n, RpcCallNodeInfo (storage_units n) hvs) | n <- good_nodes]
   return $ fillUpList (fillPairFromMaybe rpcResultNodeBroken pickPairUnique)
       nodes rpcres
diff --git a/src/Ganeti/Query/Query.hs b/src/Ganeti/Query/Query.hs
index 7ccc4db..ace0f8f 100644
--- a/src/Ganeti/Query/Query.hs
+++ b/src/Ganeti/Query/Query.hs
@@ -82,7 +82,7 @@
 import Ganeti.Config
 import Ganeti.Errors
 import Ganeti.JQueue
-import Ganeti.JSON
+import Ganeti.JSON (Container, GenericContainer(..))
 import Ganeti.Locking.Allocation (OwnerState, LockRequest(..), OwnerState(..))
 import Ganeti.Locking.Locks (GanetiLocks, ClientId, lockName)
 import Ganeti.Logging
diff --git a/src/Ganeti/Query/Server.hs b/src/Ganeti/Query/Server.hs
index 89c8b60..aefe129 100644
--- a/src/Ganeti/Query/Server.hs
+++ b/src/Ganeti/Query/Server.hs
@@ -458,19 +458,8 @@
                         else showJSON (False, genericResult id (const "") res))
               $ annotated_results
 
-handleCall _ _ cfg (WaitForJobChange jid fields prev_job prev_log tmout) = do
-  let compute_fn = computeJobUpdate cfg jid fields prev_log
-  qDir <- queueDir
-  -- verify if the job is finalized, and return immediately in this case
-  jobresult <- loadJobFromDisk qDir False jid
-  case jobresult of
-    Bad s -> return . Bad $ JobLost s
-    Ok (job, _) | not (jobFinalized job) -> do
-      let jobfile = liveJobFile qDir jid
-      answer <- watchFile jobfile (min tmout C.luxiWfjcTimeout)
-                  (prev_job, JSArray []) compute_fn
-      return . Ok $ showJSON answer
-    _ -> liftM (Ok . showJSON) compute_fn
+handleCall _ _ cfg (WaitForJobChange jid fields prev_job prev_log tmout) =
+  waitForJobChange jid prev_job tmout $ computeJobUpdate cfg jid fields prev_log
 
 handleCall _ _ cfg (SetWatcherPause time) = do
   let mcs = Config.getMasterOrCandidates cfg
@@ -569,6 +558,30 @@
 
 {-# ANN handleCall "HLint: ignore Too strict if" #-}
 
+-- | Special-case handler for WaitForJobChange RPC call for fields == ["status"]
+-- that doesn't require the use of ConfigData
+handleWaitForJobChangeStatus :: JobId -> JSValue -> JSValue -> Int
+                                -> IO (ErrorResult JSValue)
+handleWaitForJobChangeStatus jid prev_job prev_log tmout =
+  waitForJobChange jid prev_job tmout $ computeJobUpdateStatus jid prev_log
+
+-- | Common WaitForJobChange functionality shared between handleCall and
+-- handleWaitForJobChangeStatus
+waitForJobChange :: JobId -> JSValue -> Int -> IO (JSValue, JSValue)
+                          -> IO (ErrorResult JSValue)
+waitForJobChange jid prev_job tmout compute_fn = do
+  qDir <- queueDir
+  -- verify if the job is finalized, and return immediately in this case
+  jobresult <- loadJobFromDisk qDir False jid
+  case jobresult of
+    Bad s -> return . Bad $ JobLost s
+    Ok (job, _) | not (jobFinalized job) -> do
+      let jobfile = liveJobFile qDir jid
+      answer <- watchFile jobfile (min tmout C.luxiWfjcTimeout)
+                  (prev_job, JSArray []) compute_fn
+      return . Ok $ showJSON answer
+    _ -> liftM (Ok . showJSON) compute_fn
+
 -- | Query the status of a job and return the requested fields
 -- and the logs newer than the given log number.
 computeJobUpdate :: ConfigData -> JobId -> [String] -> JSValue
@@ -591,6 +604,26 @@
   logDebug $ "Updates for job " ++ sjid ++ " are " ++ encode (rfields, rlogs)
   return (JSArray rfields, rlogs)
 
+-- | A version of computeJobUpdate hardcoded to only return logs and the status
+-- field. By hardcoding this we avoid using the luxi Query infrastructure and
+-- the ConfigData value it requires.
+computeJobUpdateStatus :: JobId -> JSValue -> IO (JSValue, JSValue)
+computeJobUpdateStatus jid prev_log = do
+  qdir <- queueDir
+  loadResult <- loadJobFromDisk qdir True jid
+  let sjid = show $ fromJobId jid
+  logDebug $ "Inspecting status of job " ++ sjid
+  let (rfields, rlogs) = case loadResult of
+       Ok (job, _) -> (J.JSArray [status], newlogs)
+          where status  = showJSON $ calcJobStatus job -- like "status" jobField
+                oplogs  = map qoLog (qjOps job)        -- like "oplog" jobField
+                newer   = case J.readJSON prev_log of
+                  J.Ok n -> (\(idx, _time, _type, _msg) -> n < idx)
+                  _      -> const True
+                newlogs = showJSON $ concatMap (filter newer) oplogs
+       _ -> (JSArray[JSNull], JSArray [])
+  logDebug $ "Updates for job " ++ sjid ++ " are " ++ encode (rfields, rlogs)
+  return (rfields, rlogs)
 
 type LuxiConfig = (Lock, JQStatus, ConfigReader)
 
@@ -598,10 +631,20 @@
     :: LuxiConfig
     -> LuxiOp
     -> IO (Bool, GenericResult GanetiException JSValue)
-luxiExec (qlock, qstat, creader) args = do
-  cfg <- creader
-  result <- handleCallWrapper qlock qstat cfg args
-  return (True, result)
+luxiExec (qlock, qstat, creader) args =
+  case args of
+    -- Special case WaitForJobChange handling to avoid passing a ConfigData to
+    -- a potentially long-lived thread. ConfigData uses lots of heap, and
+    -- multiple handler threads retaining different versions of ConfigData
+    -- increases luxi's memory use for concurrent jobs that modify config.
+    WaitForJobChange jid fields prev_job prev_log tmout
+      | fields == ["status"] -> do
+        result <- handleWaitForJobChangeStatus jid prev_job prev_log tmout
+        return (True, result)
+    _ -> do
+     cfg <- creader
+     result <- handleCallWrapper qlock qstat cfg args
+     return (True, result)
 
 luxiHandler :: LuxiConfig -> U.Handler LuxiOp IO JSValue
 luxiHandler cfg = U.Handler { U.hParse         = decodeLuxiCall
diff --git a/src/Ganeti/Rpc.hs b/src/Ganeti/Rpc.hs
index ddd947c..838575f 100644
--- a/src/Ganeti/Rpc.hs
+++ b/src/Ganeti/Rpc.hs
@@ -111,7 +111,8 @@
 import Control.Monad
 import qualified Data.ByteString.Lazy.Char8 as BL
 import qualified Data.Map as Map
-import Data.Maybe (fromMaybe, mapMaybe)
+import Data.List (zipWith4)
+import Data.Maybe (mapMaybe)
 import qualified Text.JSON as J
 import Text.JSON.Pretty (pp_value)
 import qualified Data.ByteString.Base64.Lazy as Base64
@@ -128,7 +129,7 @@
 import Ganeti.Codec
 import Ganeti.Curl.Multi
 import Ganeti.Errors
-import Ganeti.JSON
+import Ganeti.JSON (ArrayObject(..), GenericContainer(..))
 import Ganeti.Logging
 import Ganeti.Objects
 import Ganeti.Runtime
@@ -179,8 +180,8 @@
   -- | Calculate the timeout value for the call execution.
   rpcCallTimeout :: a -> Int
   -- | Prepare arguments of the call to be send as POST.
-  rpcCallData :: Node -> a -> String
-  rpcCallData _ = J.encode . J.JSArray . toJSArray
+  rpcCallData :: a -> String
+  rpcCallData = J.encode . J.JSArray . toJSArray
   -- | Whether we accept offline nodes when making a call.
   rpcCallAcceptOffline :: a -> Bool
 
@@ -213,12 +214,12 @@
 
 -- | Create HTTP request for a given node provided it is online,
 -- otherwise create empty response.
-prepareHttpRequest :: (RpcCall a) => Int -> [CurlOption] -> Node -> a
-                   -> ERpcError HttpClientRequest
-prepareHttpRequest port opts node call
+prepareHttpRequest :: (RpcCall a) => Int -> [CurlOption] -> Node
+                   -> String -> a -> ERpcError HttpClientRequest
+prepareHttpRequest port opts node reqdata call
   | rpcCallAcceptOffline call || not (nodeOffline node) =
       Right HttpClientRequest { requestUrl  = prepareUrl port node call
-                              , requestData = rpcCallData node call
+                              , requestData = reqdata
                               , requestOpts = opts ++ curlOpts
                               }
   | otherwise = Left OfflineNodeError
@@ -275,9 +276,13 @@
                . liftM (fromIntegral . servicePort)
                $ getServiceByName C.noded "tcp"
 
--- | Execute multiple RPC calls in parallel
+-- | Execute multiple distinct RPC calls in parallel
 executeRpcCalls :: (Rpc a b) => [(Node, a)] -> IO [(Node, ERpcError b)]
-executeRpcCalls nodeCalls = do
+executeRpcCalls = executeRpcCalls' . map (\(n, c) -> (n, c, rpcCallData c))
+
+-- | Execute multiple RPC calls in parallel
+executeRpcCalls' :: (Rpc a b) => [(Node, a, String)] -> IO [(Node, ERpcError b)]
+executeRpcCalls' nodeCalls = do
   port <- getNodedPort
   cert_file <- P.nodedCertFile
   client_cert_file_name <- P.nodedClientCertFile
@@ -287,16 +292,16 @@
   let client_cert_file = if client_file_exists
                          then client_cert_file_name
                          else cert_file
-      (nodes, calls) = unzip nodeCalls
+      (nodes, calls, datas) = unzip3 nodeCalls
       opts = map (getOptionsForCall cert_file client_cert_file) calls
-      opts_urls = zipWith3 (\n c o ->
-                         case prepareHttpRequest port o n c of
+      opts_urls = zipWith4 (\n c d o ->
+                         case prepareHttpRequest port o n d c of
                            Left v -> Left v
                            Right request ->
                              Right (CurlPostFields [requestData request]:
                                     requestOpts request,
                                     requestUrl request)
-                    ) nodes calls opts
+                    ) nodes calls datas opts
   -- split the opts_urls list; we don't want to pass the
   -- failed-already nodes to Curl
   let (lefts, rights, trail) = splitEithers opts_urls
@@ -311,8 +316,10 @@
   return pairedList
 
 -- | Execute an RPC call for many nodes in parallel.
+-- NB this computes the RPC call payload string only once.
 executeRpcCall :: (Rpc a b) => [Node] -> a -> IO [(Node, ERpcError b)]
-executeRpcCall nodes call = executeRpcCalls . zip nodes $ repeat call
+executeRpcCall nodes call = executeRpcCalls' [(n, call, rpc_data) | n <- nodes]
+  where rpc_data = rpcCallData call
 
 -- | Helper function that is used to read dictionaries of values.
 sanitizeDictResults :: [(String, J.Result a)] -> ERpcError [(String, a)]
@@ -431,7 +438,7 @@
   rpcCallName _          = "all_instances_info"
   rpcCallTimeout _       = rpcTimeoutToRaw Urgent
   rpcCallAcceptOffline _ = False
-  rpcCallData _ call     = J.encode (
+  rpcCallData call       = J.encode (
     map fst $ rpcCallAllInstInfoHypervisors call,
     GenericContainer . Map.fromList $ rpcCallAllInstInfoHypervisors call)
 
@@ -486,7 +493,7 @@
   rpcCallName _          = "instance_console_info"
   rpcCallTimeout _       = rpcTimeoutToRaw Urgent
   rpcCallAcceptOffline _ = False
-  rpcCallData _ call     = J.encode .
+  rpcCallData call       = J.encode .
     GenericContainer $ Map.fromList (rpcCallInstConsInfoInstanceInfo call)
 
 instance Rpc RpcCallInstanceConsoleInfo RpcResultInstanceConsoleInfo where
@@ -522,7 +529,7 @@
 
 -- | Returns node information
 $(buildObject "RpcCallNodeInfo" "rpcCallNodeInfo"
-  [ simpleField "storage_units" [t| Map.Map String [StorageUnit] |]
+  [ simpleField "storage_units" [t| [StorageUnit] |]
   , simpleField "hypervisors" [t| [ (Hypervisor, HvParams) ] |]
   ])
 
@@ -557,10 +564,8 @@
   rpcCallName _          = "node_info"
   rpcCallTimeout _       = rpcTimeoutToRaw Urgent
   rpcCallAcceptOffline _ = False
-  rpcCallData n call     = J.encode
-    ( fromMaybe (error $ "Programmer error: missing parameter for node named "
-                         ++ nodeName n)
-          $ Map.lookup (uuidOf n) (rpcCallNodeInfoStorageUnits call)
+  rpcCallData call       = J.encode
+    ( rpcCallNodeInfoStorageUnits call
     , rpcCallNodeInfoHypervisors call
     )
 
@@ -582,7 +587,7 @@
   rpcCallName _          = "version"
   rpcCallTimeout _       = rpcTimeoutToRaw Urgent
   rpcCallAcceptOffline _ = True
-  rpcCallData _          = J.encode
+  rpcCallData            = J.encode
 
 instance Rpc RpcCallVersion RpcResultVersion where
   rpcResultFill _ res = fromJSValueToRes res RpcResultVersion
@@ -651,7 +656,7 @@
   rpcCallName _          = "export_list"
   rpcCallTimeout _       = rpcTimeoutToRaw Fast
   rpcCallAcceptOffline _ = False
-  rpcCallData _          = J.encode
+  rpcCallData            = J.encode
 
 instance Rpc RpcCallExportList RpcResultExportList where
   rpcResultFill _ res = fromJSValueToRes res RpcResultExportList
@@ -671,7 +676,7 @@
   rpcCallName _          = "jobqueue_update"
   rpcCallTimeout _       = rpcTimeoutToRaw Fast
   rpcCallAcceptOffline _ = False
-  rpcCallData _ call     = J.encode
+  rpcCallData call       = J.encode
     ( rpcCallJobqueueUpdateFileName call
     , toCompressed $ rpcCallJobqueueUpdateContent call
     )
diff --git a/src/Ganeti/Storage/Drbd/Types.hs b/src/Ganeti/Storage/Drbd/Types.hs
index a60c510..1fb9073 100644
--- a/src/Ganeti/Storage/Drbd/Types.hs
+++ b/src/Ganeti/Storage/Drbd/Types.hs
@@ -54,7 +54,7 @@
 import Text.JSON
 import Text.Printf
 
-import Ganeti.JSON
+import Ganeti.JSON (optFieldsToObj, optionalJSField)
 
 --TODO: consider turning deviceInfos into an IntMap
 -- | Data type contaning all the data about the status of DRBD.
diff --git a/src/Ganeti/Storage/Utils.hs b/src/Ganeti/Storage/Utils.hs
index 9cfdd7e..f7191f3 100644
--- a/src/Ganeti/Storage/Utils.hs
+++ b/src/Ganeti/Storage/Utils.hs
@@ -33,7 +33,7 @@
 -}
 
 module Ganeti.Storage.Utils
-  ( getStorageUnitsOfNodes
+  ( getStorageUnitsOfNode
   , nodesWithValidConfig
   ) where
 
@@ -45,7 +45,6 @@
 import Control.Monad
 import Data.List (nub)
 import Data.Maybe
-import qualified Data.Map as M
 
 -- | Get the cluster's default storage unit for a given disk template
 getDefaultStorageKey :: ConfigData -> DiskTemplate -> Maybe StorageKey
@@ -94,8 +93,3 @@
   let clusterSUs = getClusterStorageUnitRaws cfg
       es = fromJust (getExclusiveStorage cfg n)
   in  map (addParamsToStorageUnit es) clusterSUs
-
--- | Get the storage unit map for all nodes
-getStorageUnitsOfNodes :: ConfigData -> [Node] -> M.Map String [StorageUnit]
-getStorageUnitsOfNodes cfg ns =
-  M.fromList (map (\n -> (uuidOf n, getStorageUnitsOfNode cfg n)) ns)
diff --git a/src/Ganeti/THH.hs b/src/Ganeti/THH.hs
index 4cb610e..4bc7e88 100644
--- a/src/Ganeti/THH.hs
+++ b/src/Ganeti/THH.hs
@@ -104,7 +104,7 @@
 import qualified Text.JSON as JSON
 import Text.JSON.Pretty (pp_value)
 
-import Ganeti.JSON
+import Ganeti.JSON (readJSONWithDesc, fromObj, DictObject(..), ArrayObject(..), maybeFromObj, mkUsedKeys, showJSONtoDict, readJSONfromDict, branchOnField, addField, allUsedKeys)
 import Ganeti.PartialParams
 import Ganeti.PyValue
 import Ganeti.THH.PyType
@@ -310,15 +310,16 @@
 -- | Checks that a given field is not optional (for object types or
 -- fields which should not allow this case).
 checkNonOptDef :: (Monad m) => Field -> m ()
-checkNonOptDef (Field { fieldIsOptional = OptionalOmitNull
-                      , fieldName = name }) =
-  fail $ "Optional field " ++ (T.unpack name) ++ " used in parameter declaration"
-checkNonOptDef (Field { fieldIsOptional = OptionalSerializeNull
-                      , fieldName = name }) =
-  fail $ "Optional field " ++ (T.unpack name) ++ " used in parameter declaration"
-checkNonOptDef (Field { fieldDefault = (Just _), fieldName = name }) =
-  fail $ "Default field " ++ (T.unpack name) ++ " used in parameter declaration"
-checkNonOptDef _ = return ()
+checkNonOptDef field
+  | fieldIsOptional field == OptionalOmitNull       = failWith kOpt
+  | fieldIsOptional field == OptionalSerializeNull  = failWith kOpt
+  | isJust (fieldDefault field)                     = failWith kDef
+  | otherwise                                       = return ()
+  where failWith kind = fail $ kind ++ " field " ++ name
+                                    ++ " used in parameter declaration"
+        name = T.unpack (fieldName field)
+        kOpt = "Optional"
+        kDef = "Default"
 
 -- | Construct a function that parses a field value. If the field has
 -- a custom 'fieldRead', it's applied to @o@ and used. Otherwise
@@ -328,8 +329,9 @@
         -> Q Exp   -- ^ The resulting function that parses a JSON message
 parseFn field o =
   let fnType = [t| JSON.JSValue -> JSON.Result $(fieldType field) |]
-      expr = maybe [| readJSONWithDesc $(stringE . T.unpack $ fieldName field) |]
-                   (`appE` o) (fieldRead field)
+      expr = maybe
+               [| readJSONWithDesc $(stringE . T.unpack $ fieldName field) |]
+               (`appE` o) (fieldRead field)
   in sigE expr fnType
 
 -- | Produces the expression that will de-serialise a given
@@ -806,7 +808,7 @@
 genOpConsFields :: OpCodeConstructor -> Clause
 genOpConsFields (cname, _, _, fields, _) =
   let op_id = deCamelCase cname
-      fieldnames f = (T.unpack . fieldName $ f):(map T.unpack $ fieldExtraKeys f)
+      fieldnames f = map T.unpack $ fieldName f:fieldExtraKeys f
       fvals = map (LitE . StringL) . sort . nub $ concatMap fieldnames fields
   in Clause [LitP (StringL op_id)] (NormalB $ ListE fvals) []
 
diff --git a/src/Ganeti/THH/Field.hs b/src/Ganeti/THH/Field.hs
index 6047ca4..9b444e9 100644
--- a/src/Ganeti/THH/Field.hs
+++ b/src/Ganeti/THH/Field.hs
@@ -57,7 +57,7 @@
 import System.Posix.Types (FileMode, ProcessID)
 import System.Time (ClockTime(..))
 
-import Ganeti.JSON
+import Ganeti.JSON (TimeAsDoubleJSON(..))
 import Ganeti.THH
 
 -- * Internal functions
diff --git a/src/Ganeti/THH/RPC.hs b/src/Ganeti/THH/RPC.hs
index 1cb63ec..25388df 100644
--- a/src/Ganeti/THH/RPC.hs
+++ b/src/Ganeti/THH/RPC.hs
@@ -55,7 +55,7 @@
 
 import Ganeti.BasicTypes
 import Ganeti.Errors
-import Ganeti.JSON
+import Ganeti.JSON (fromJResultE, fromJVal)
 import Ganeti.THH.Types
 import qualified Ganeti.UDSServer as US
 
diff --git a/src/Ganeti/Types.hs b/src/Ganeti/Types.hs
index 437e62a..8da06d4 100644
--- a/src/Ganeti/Types.hs
+++ b/src/Ganeti/Types.hs
@@ -201,7 +201,7 @@
 import System.Time (ClockTime)
 
 import qualified Ganeti.ConstantUtils as ConstantUtils
-import Ganeti.JSON
+import Ganeti.JSON (Container, HasStringRepr(..))
 import qualified Ganeti.THH as THH
 import Ganeti.Utils
 
diff --git a/src/Ganeti/UDSServer.hs b/src/Ganeti/UDSServer.hs
index 8478e2d..7008d08 100644
--- a/src/Ganeti/UDSServer.hs
+++ b/src/Ganeti/UDSServer.hs
@@ -97,7 +97,7 @@
 
 import Ganeti.BasicTypes
 import Ganeti.Errors (GanetiException(..), ErrorResult)
-import Ganeti.JSON
+import Ganeti.JSON (fromJResult, fromJVal, fromJResultE, fromObj)
 import Ganeti.Logging
 import Ganeti.THH
 import Ganeti.Utils
diff --git a/src/Ganeti/WConfd/Ssconf.hs b/src/Ganeti/WConfd/Ssconf.hs
index b8c83c0..3900578 100644
--- a/src/Ganeti/WConfd/Ssconf.hs
+++ b/src/Ganeti/WConfd/Ssconf.hs
@@ -53,7 +53,7 @@
 import Ganeti.BasicTypes
 import Ganeti.Config
 import Ganeti.Constants
-import Ganeti.JSON
+import Ganeti.JSON (fromContainer, lookupContainer)
 import Ganeti.Objects
 import Ganeti.Ssconf
 import Ganeti.Utils
diff --git a/test/hs/Test/Ganeti/OpCodes.hs b/test/hs/Test/Ganeti/OpCodes.hs
index 4d2167e..603c394 100644
--- a/test/hs/Test/Ganeti/OpCodes.hs
+++ b/test/hs/Test/Ganeti/OpCodes.hs
@@ -638,7 +638,7 @@
       extra_hs = hs_ops \\ py_ops
   HUnit.assertBool ("Missing OpCodes from the Haskell code:\n" ++
                     unlines extra_py) (null extra_py)
-  HUnit.assertBool ("Extra OpCodes in the Haskell code code:\n" ++
+  HUnit.assertBool ("Extra OpCodes in the Haskell code:\n" ++
                     unlines extra_hs) (null extra_hs)
 
 -- | Custom HUnit test case that forks a Python process and checks
diff --git a/test/hs/Test/Ganeti/Rpc.hs b/test/hs/Test/Ganeti/Rpc.hs
index 86b3ece..bdb83ac 100644
--- a/test/hs/Test/Ganeti/Rpc.hs
+++ b/test/hs/Test/Ganeti/Rpc.hs
@@ -73,13 +73,6 @@
   num_storage_units <- choose (0, 5)
   vectorOf num_storage_units genStorageUnit
 
-genStorageUnitMap :: Gen (Map.Map String [StorageUnit])
-genStorageUnitMap = do
-  num_nodes <- choose (0,5)
-  node_uuids <- vectorOf num_nodes genName
-  storage_units_list <- vectorOf num_nodes genStorageUnits
-  return $ Map.fromList (zip node_uuids storage_units_list)
-
 -- FIXME: Generate more interesting hvparams
 -- | Generate Hvparams
 genHvParams :: Gen Objects.HvParams
@@ -101,7 +94,7 @@
   arbitrary = Rpc.RpcCallInstanceList <$> arbitrary
 
 instance Arbitrary Rpc.RpcCallNodeInfo where
-  arbitrary = Rpc.RpcCallNodeInfo <$> genStorageUnitMap <*> genHvSpecs
+  arbitrary = Rpc.RpcCallNodeInfo <$> genStorageUnits <*> genHvSpecs
 
 -- | Generates per-instance console info params for the 'InstanceConsoleInfo'
 -- call.
diff --git a/test/py/mocks.py b/test/py/mocks.py
index 406caca..b48125b 100644
--- a/test/py/mocks.py
+++ b/test/py/mocks.py
@@ -113,6 +113,7 @@
 
 class FakeContext(object):
   """Fake context object"""
+  # pylint: disable=W0613
 
   def __init__(self):
     self.cfg = FakeConfig()
@@ -124,9 +125,10 @@
   def GetRpc(self, cfg):
     return None
 
-  def GetWConfdContext(self, _ec_id):
+  def GetWConfdContext(self, ec_id):
     return (None, None, None)
 
+
 class FakeGetentResolver(object):
   """Fake runtime.GetentResolver"""
 
@@ -154,6 +156,7 @@
   def LookupGid(self, gid):
     return "group%s" % gid
 
+
 class FakeLU(object):
   HPATH = "fake-lu"
   HTYPE = None
@@ -161,7 +164,7 @@
   def __init__(self, processor, op, cfg, rpc_runner, prereq_err):
     self.proc = processor
     self.cfg = cfg
-    self.op  = op
+    self.op = op
     self.rpc = rpc_runner
     self.prereq_err = prereq_err
 
@@ -170,7 +173,7 @@
     self.dont_collate_locks = dict.fromkeys(locking.LEVELS, False)
     self.add_locks = {}
 
-    self.LogWarning = processor.LogWarning
+    self.LogWarning = processor.LogWarning # pylint: disable=C0103
 
   def CheckArguments(self):
     pass
@@ -184,7 +187,6 @@
   def CheckPrereq(self):
     if self.prereq_err:
       raise self.prereq_err
-    pass
 
   def Exec(self, feedback_fn):
     pass
@@ -196,7 +198,9 @@
     return {}
 
   def PreparePostHookNodes(self, post_hook_node_uuids):
+    # pylint: disable=W0613
     return []
 
   def HooksCallBack(self, phase, hook_results, feedback_fn, lu_result):
+    # pylint: disable=W0613
     return lu_result
diff --git a/test/py/testutils_ssh.py b/test/py/testutils_ssh.py
index fa3b35d..e700e47 100644
--- a/test/py/testutils_ssh.py
+++ b/test/py/testutils_ssh.py
@@ -564,7 +564,7 @@
         uuid=old_node_data.uuid,
         key=new_key,
         is_potential_master_candidate=old_node_data
-            .is_potential_master_candidate,
+          .is_potential_master_candidate,
         is_master_candidate=old_node_data.is_master_candidate,
         is_master=old_node_data.is_master)