Change return type of internal rmJob

...to also provide the job itself. In this way, the function can
also be used for tasks that require temporarily removing a job
from the queue.
Signed-off-by: Klaus Aehlig <aehlig@google.com>
Reviewed-by: Petr Pudlak <pudlak@google.com>

src/Ganeti/JQScheduler.hs

@@ -300,19 +300,21 @@ enqueueNewJobs state jobs = do
   scheduleSomeJobs state
 
 -- | Pure function for removing a queued job from the job queue by
--- atomicModifyIORef. The answer is True if the job could be removed
+-- atomicModifyIORef. The answer is Just the job if the job could be removed
+-- before being handed over to execution, Nothing if it already was started
 -- and a Bad result if the job is not found in the queue.
--- and a Bad result if the job is not found in the queue.
+rmJob :: JobId -> Queue -> (Queue, Result (Maybe QueuedJob))
 rmJob jid q =
   let isJid = (jid ==) . qjId . jJob
       (found, queued') = partition isJid $ qEnqueued q
-      (found, queued') = partition isJid $ qEnqueued q
-  in if null found
-       then if any isJid $ qRunning q
-              then (q, Ok False)
-              else (q, Bad $ "Job " ++ show (fromJobId jid)
-                              ++ " unknown to the queue")
+      isRunning = any isJid $ qRunning q
+      sJid = (++) "Job " . show $ fromJobId jid
+  in case (found, isRunning) of
+    ([job], _) -> (q {qEnqueued = queued'}, Ok . Just $ jJob job)
+    (_:_, _) -> (q, Bad $ "Queue in inconsistent state."
+                           ++ sJid ++ " queued multiple times")
+    (_, True) -> (q, Ok Nothing)
+    _ -> (q, Bad $ sJid ++ " not found in queue")
 
 -- | Try to remove a queued job from the job queue. Return True, if
 -- the job could be removed from the queue before being handed over
@@ -321,6 +323,7 @@ rmJob jid q =
 dequeueJob :: JQStatus -> JobId -> IO (Result Bool)
 dequeueJob state jid = do
   result <- atomicModifyIORef (jqJobs state) $ rmJob jid
+  let result' = fmap isJust result
   logDebug $ "Result of dequeing job " ++ show (fromJobId jid)
-              ++ " is " ++ show result
-  return result
+              ++ " is " ++ show result'
+  return result'