Implement ChangeJobPriority in luxid

For jobs still queued, we ask the queue to change the priority,
and replicate the changed job. For jobs that have already been
started, we have to contact the job directly, which, at the moment,
means forwarding the request to masterd.
Signed-off-by: Klaus Aehlig <aehlig@google.com>
Reviewed-by: Petr Pudlak <pudlak@google.com>

src/Ganeti/Query/Server.hs

@@ -33,6 +33,7 @@ import Control.Applicative
 import Control.Concurrent
 import Control.Exception
 import Control.Monad (forever, when, zipWithM, liftM)
+import Control.Monad.IO.Class
 import Data.Bits (bitSize)
 import qualified Data.Set as Set (toList)
 import Data.IORef
@@ -57,7 +58,8 @@ import Ganeti.Logging
 import Ganeti.Luxi
 import qualified Ganeti.Query.Language as Qlang
 import qualified Ganeti.Query.Cluster as QCluster
-import Ganeti.Path (queueDir, jobQueueLockFile, jobQueueDrainFile)
+import Ganeti.Path ( queueDir, jobQueueLockFile, jobQueueDrainFile
+                   , defaultMasterSocket)
 import Ganeti.Rpc
 import Ganeti.Query.Query
 import Ganeti.Query.Filter (makeSimpleFilter)
@@ -303,6 +305,24 @@ handleCall _ _ cfg (SetDrainFlag value) = do
   _ <- executeRpcCall mcs $ RpcCallSetDrainFlag value
   return . Ok . showJSON $ True
 
+handleCall _ qstat cfg (ChangeJobPriority jid prio) = do
+  maybeJob <- setJobPriority qstat jid prio
+  case maybeJob of
+    Bad s -> return . Ok $ showJSON (False, s)
+    Ok (Just job) -> runResultT $ do
+      let mcs = Config.getMasterCandidates cfg
+      qDir <- liftIO queueDir
+      liftIO $ replicateManyJobs qDir mcs [job]
+      return $ showJSON (True, "Priorities of pending opcodes for job "
+                               ++ show (fromJobId jid) ++ " have been changed"
+                               ++ " to " ++ show prio)
+    Ok Nothing -> runResultT $ do
+      -- Job has already started; so we have to forward the request
+      -- to the job, currently handled by masterd.
+      socketpath <- liftIO defaultMasterSocket
+      cl <- liftIO $ getLuxiClient socketpath
+      ResultT $ callMethod (ChangeJobPriority jid prio) cl
+
 handleCall _ qstat  cfg (CancelJob jid) = do
   let jName = (++) "job " . show $ fromJobId jid
   dequeueResult <- dequeueJob qstat jid