root / src / Ganeti / JQScheduler.hs @ 1b3bde96
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{-| Implementation of a reader for the job queue. |
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-} |
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{- |
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Copyright (C) 2013 Google Inc. |
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This program is free software; you can redistribute it and/or modify |
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it under the terms of the GNU General Public License as published by |
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the Free Software Foundation; either version 2 of the License, or |
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(at your option) any later version. |
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This program is distributed in the hope that it will be useful, but |
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WITHOUT ANY WARRANTY; without even the implied warranty of |
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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General Public License for more details. |
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|
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You should have received a copy of the GNU General Public License |
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along with this program; if not, write to the Free Software |
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Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA |
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02110-1301, USA. |
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-} |
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module Ganeti.JQScheduler |
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( JQStatus |
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, emptyJQStatus |
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, initJQScheduler |
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, enqueueNewJobs |
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) where |
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import Control.Arrow |
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import Control.Concurrent |
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import Control.Exception |
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import Control.Monad |
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import Data.List |
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import Data.IORef |
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import Ganeti.BasicTypes |
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import Ganeti.Constants as C |
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import Ganeti.JQueue as JQ |
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import Ganeti.Logging |
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import Ganeti.Path |
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import Ganeti.Types |
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import Ganeti.Utils |
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data JobWithStat = JobWithStat { jStat :: FStat, jJob :: QueuedJob } |
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data Queue = Queue { qEnqueued :: [JobWithStat], qRunning :: [JobWithStat] } |
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{-| Representation of the job queue |
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We keep two lists of jobs (together with information about the last |
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fstat result observed): the jobs that are enqueued, but not yet handed |
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over for execution, and the jobs already handed over for execution. They |
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are kept together in a single IORef, so that we can atomically update |
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both, in particular when scheduling jobs to be handed over for execution. |
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-} |
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data JQStatus = JQStatus |
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{ jqJobs :: IORef Queue |
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} |
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emptyJQStatus :: IO JQStatus |
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emptyJQStatus = do |
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jqJ <- newIORef Queue {qEnqueued=[], qRunning=[]} |
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return JQStatus { jqJobs=jqJ } |
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-- | Apply a function on the running jobs. |
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onRunningJobs :: ([JobWithStat] -> [JobWithStat]) -> Queue -> Queue |
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onRunningJobs f queue = queue {qRunning=f $ qRunning queue} |
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-- | Apply a function on the queued jobs. |
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onQueuedJobs :: ([JobWithStat] -> [JobWithStat]) -> Queue -> Queue |
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onQueuedJobs f queue = queue {qEnqueued=f $ qEnqueued queue} |
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-- | Obtain a JobWithStat from a QueuedJob. |
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unreadJob :: QueuedJob -> JobWithStat |
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unreadJob job = JobWithStat {jJob=job, jStat=nullFStat} |
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-- | Reload interval for polling the running jobs for updates in microseconds. |
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watchInterval :: Int |
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watchInterval = C.luxidJobqueuePollInterval * 1000000 |
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-- | Maximal number of jobs to be running at the same time. |
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maxRunningJobs :: Int |
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maxRunningJobs = C.luxidMaximalRunningJobs |
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-- | Wrapper function to atomically update the jobs in the queue status. |
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modifyJobs :: JQStatus -> (Queue -> Queue) -> IO () |
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modifyJobs qstat f = atomicModifyIORef (jqJobs qstat) (flip (,) () . f) |
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-- | Reread a job from disk, if the file has changed. |
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readJobStatus :: JobWithStat -> IO (Maybe JobWithStat) |
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readJobStatus (JobWithStat {jStat=fstat, jJob=job}) = do |
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let jid = qjId job |
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qdir <- queueDir |
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let fpath = liveJobFile qdir jid |
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logDebug $ "Checking if " ++ fpath ++ " changed on disk." |
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changedResult <- try $ needsReload fstat fpath |
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:: IO (Either IOError (Maybe FStat)) |
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let changed = either (const $ Just nullFStat) id changedResult |
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case changed of |
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Nothing -> do |
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logDebug $ "File " ++ fpath ++ " not changed on disk." |
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return Nothing |
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Just fstat' -> do |
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let jids = show $ fromJobId jid |
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logInfo $ "Rereading job " ++ jids |
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readResult <- loadJobFromDisk qdir True jid |
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case readResult of |
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Bad s -> do |
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logWarning $ "Failed to read job " ++ jids ++ ": " ++ s |
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return Nothing |
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Ok (job', _) -> do |
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logDebug |
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$ "Read job " ++ jids ++ ", staus is " ++ show (calcJobStatus job') |
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return . Just $ JobWithStat {jStat=fstat', jJob=job'} |
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-- | Update a job in the job queue, if it is still there. This is the |
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-- pure function for inserting a previously read change into the queue. |
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-- as the change contains its time stamp, we don't have to worry about a |
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-- later read change overwriting a newer read state. If this happens, the |
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-- fstat value will be outdated, so the next poller run will fix this. |
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updateJobStatus :: JobWithStat -> [JobWithStat] -> [JobWithStat] |
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updateJobStatus job' = |
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let jid = qjId $ jJob job' in |
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map (\job -> if qjId (jJob job) == jid then job' else job) |
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-- | Update a single job by reading it from disk, if necessary. |
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updateJob :: JQStatus -> JobWithStat -> IO () |
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updateJob state jb = do |
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jb' <- readJobStatus jb |
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maybe (return ()) (modifyJobs state . onRunningJobs . updateJobStatus) jb' |
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-- | Sort out the finished jobs from the monitored part of the queue. |
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-- This is the pure part, splitting the queue into a remaining queue |
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-- and the jobs that were removed. |
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sortoutFinishedJobs :: Queue -> (Queue, [QueuedJob]) |
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sortoutFinishedJobs queue = |
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let (fin, run') = partition (jobFinalized . jJob) . qRunning $ queue |
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in (queue {qRunning=run'}, map jJob fin) |
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-- | Actually clean up the finished jobs. This is the IO wrapper around |
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-- the pure `sortoutFinishedJobs`. |
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cleanupFinishedJobs :: JQStatus -> IO () |
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cleanupFinishedJobs qstate = do |
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finished <- atomicModifyIORef (jqJobs qstate) sortoutFinishedJobs |
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let showJob = show . ((fromJobId . qjId) &&& calcJobStatus) |
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jlist = commaJoin $ map showJob finished |
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unless (null finished) |
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. logInfo $ "Finished jobs: " ++ jlist |
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-- | Decide on which jobs to schedule next for execution. This is the |
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-- pure function doing the scheduling. |
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selectJobsToRun :: Queue -> (Queue, [QueuedJob]) |
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selectJobsToRun queue = |
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let n = maxRunningJobs - length (qRunning queue) |
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(chosen, remain) = splitAt n (qEnqueued queue) |
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in (queue {qEnqueued=remain, qRunning=qRunning queue ++ chosen} |
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, map jJob chosen) |
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-- | Requeue jobs that were previously selected for execution |
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-- but couldn't be started. |
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requeueJobs :: JQStatus -> [QueuedJob] -> IOError -> IO () |
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requeueJobs qstate jobs err = do |
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let jids = map qjId jobs |
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jidsString = commaJoin $ map (show . fromJobId) jids |
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rmJobs = filter ((`notElem` jids) . qjId . jJob) |
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logWarning $ "Starting jobs failed: " ++ show err |
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logWarning $ "Rescheduling jobs: " ++ jidsString |
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modifyJobs qstate (onRunningJobs rmJobs) |
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modifyJobs qstate (onQueuedJobs . (++) $ map unreadJob jobs) |
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-- | Schedule jobs to be run. This is the IO wrapper around the |
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-- pure `selectJobsToRun`. |
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scheduleSomeJobs :: JQStatus -> IO () |
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scheduleSomeJobs qstate = do |
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chosen <- atomicModifyIORef (jqJobs qstate) selectJobsToRun |
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unless (null chosen) . logInfo . (++) "Starting jobs: " . commaJoin |
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$ map (show . fromJobId . qjId) chosen |
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result <- try $ JQ.startJobs chosen |
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either (requeueJobs qstate chosen) return result |
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-- | Format the job queue status in a compact, human readable way. |
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showQueue :: Queue -> String |
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showQueue (Queue {qEnqueued=waiting, qRunning=running}) = |
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let showids = show . map (fromJobId . qjId . jJob) |
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in "Waiting jobs: " ++ showids waiting |
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++ "; running jobs: " ++ showids running |
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-- | Time-based watcher for updating the job queue. |
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onTimeWatcher :: JQStatus -> IO () |
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onTimeWatcher qstate = forever $ do |
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threadDelay watchInterval |
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logDebug "Job queue watcher timer fired" |
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jobs <- readIORef (jqJobs qstate) |
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mapM_ (updateJob qstate) $ qRunning jobs |
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cleanupFinishedJobs qstate |
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jobs' <- readIORef (jqJobs qstate) |
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logInfo $ showQueue jobs' |
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scheduleSomeJobs qstate |
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-- | Set up the job scheduler. This will also start the monitoring |
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-- of changes to the running jobs. |
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initJQScheduler :: JQStatus -> IO () |
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initJQScheduler qstate = do |
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logInfo "Starting time-based job queue watcher" |
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_ <- forkIO $ onTimeWatcher qstate |
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return () |
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-- | Enqueue new jobs. This will guarantee that the jobs will be executed |
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-- eventually. |
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enqueueNewJobs :: JQStatus -> [QueuedJob] -> IO () |
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enqueueNewJobs state jobs = do |
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logInfo . (++) "New jobs enqueued: " . commaJoin |
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$ map (show . fromJobId . qjId) jobs |
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let jobs' = map unreadJob jobs |
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modifyJobs state (onQueuedJobs (++ jobs')) |
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scheduleSomeJobs state |