Revision 155df343

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

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