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Cron data structure and parser for Haskell

License: Other

Haskell 100.00%

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Add @reboot non-standard schedule

Have you considered adding the @reboot schedule? Looking at the code it would be a bit intrusive, because it breaks the assumption that all @foo can be reduced to a timespec.

If I made a pull request, would you be interested in this?

Exposing System.Cron.Schedule.forkJob

I know this package is just "data structure and parser" by definition, but found the scheduling feature is useful.
So I want to reuse it for one of my applications which parses the schedule specification in a different format.
In such a use case, addJob, runSchedule, etc are unnecessary: calling forkJob directly with Jobs parsed by the application is sufficient and more efficient.
Can you expose System.Cron.Schedule.forkJob?

Missing test suite files

test/System/CronSpec.hs:4:8:
    Could not find module ‘SpecHelper’
    Use -v to see a list of the files searched for.

Compatibility with stackage (older transformers library)

I use stackage for everything, and I really wanted to use cron, so I forked it and made cron-compat which uses the transformers and mtl compatibility shims to add ExceptT to older versions. I mostly just wanted to put this here so that if anyone finds themselves in the same boat, they can just reuse my fork instead of redoing that work.

cron-0.3.1 can't compile its test suite

Apparently, the release tarball on Hackage is incomplete:

Preprocessing test suite 'test' for cron-0.3.1...

test/Main.hs:8:18:
    Could not find module ‘SpecHelper’
    Use -v to see a list of the files searched for.

test/Main.hs:9:18:
    Could not find module ‘System.Test.Cron’
    Use -v to see a list of the files searched for.

test/Main.hs:10:18:
    Could not find module ‘System.Test.Cron.Parser’
    Perhaps you meant
      System.Cron.Parser (from cron-0.3.1@cron_CFXF91iTeegJXloOfnE9xl)
    Use -v to see a list of the files searched for.

test/Main.hs:11:18:
    Could not find module ‘System.Test.Cron.Schedule’
    Perhaps you meant
      System.Cron.Schedule (from cron-0.3.1@cron_CFXF91iTeegJXloOfnE9xl)
    Use -v to see a list of the files searched for.

parseTimeOrError: no parse of "2020-02-24 11:60" (since LTS-15.1 migration)

Since upgrading to LTS-15.1 (which ships GHC 8.8.2), I experienced troubles with some scheduled jobs that are triggered every hour.
I get the following exception:

stacktrace-exe: parseTimeOrError: no parse of "2020-02-24 11:60"
CallStack (from HasCallStack):
  error, called at libraries/time/lib/Data/Time/Format/Parse.hs:82:12 in time-1.9.3:Data.Time.Format.Parse

The full stacktrace:

*** Exception (reporting due to +RTS -xc): (THUNK_2_0), stack trace: 
  System.Cron.Schedule.readTime',
  called from System.Cron.Schedule.findNextMinuteDelay.next,
  called from System.Cron.Schedule.findNextMinuteDelay,
  called from System.Cron.Schedule.forkJob,
  called from System.Cron.Schedule.execSchedule,
  called from Main.main
stacktrace-exe: parseTimeOrError: no parse of "2020-02-24 11:60"
CallStack (from HasCallStack):
  error, called at libraries/time/lib/Data/Time/Format/Parse.hs:82:12 in time-1.9.3:Data.Time.Format.Parse

I managed to reproduce the issue starting a project from scratch (with a stack init) as below:

main :: IO ()
main = do
  let Right cs1 = parseCronSchedule everyHour
  print $ describe defaultOpts cs1
  tids <- execSchedule $ addJob job1 everyHour
  print tids
  _ <- getLine
  pure ()

job1 :: IO ()
job1 = do
  currentTime <- getCurrentTime
  print currentTime

everyHour :: Text
everyHour = pack "0 * * * *"

For the record, the job ran fine before upgrading to LTS-15.1.
Do you have any idea about it?

Thank you in advance!

0.4.0 doesn't compile with GHC <7.10

... although advertised tested-with in the cabal file. (And bounds were allowing to build it).

src/System/Cron/Types.hs:153:55:
    Not in scope: ‘<$>’
    Perhaps you meant ‘<>’ (imported from Data.Monoid)

src/System/Cron/Types.hs:374:63:
    Not in scope: ‘<$>’
    Perhaps you meant ‘<>’ (imported from Data.Monoid)

Consider using base-compat.

Publish back on Hackage/Stackage

Current version is no longer available on Stackage nightly (thus high risk of not being available once GHC 8.8 lands there), it would be awesome to fix the build if need be then publish back please.

Passing UTCTime to Job

Thanks in advance of my request for a really useful scheduling library.

Is there any scope to extend cron so that the time it has been scheduled for is passed to the job?

Ie so the Job definition becomes something like:

data Job = Job CronSchedule (UTCTime -> IO ())

This way, systems relying on cron can be tested independently of the current wall clock time...
I realise this would break plenty of code, but maybe there is a way to add it without doing so?

Maybe something like:

data Job = Job CronSchedule (IO ())
| JobWithTime CronSchedule (UTCTime -> IO ())

I'm using a fork at https://github.com/joehealy/cron/tree/pass_time_to_jobs to achieve this, but without the backwards compatibility.

Failure to parse a schedule line should throw an exception

In a web app I'm building, I have the following lines with crontab entries that do not parse correctly:

-- Somwhere far far away in an IO monad
_ <- execSchedule $ do
  addJob (heartbeat app)                       "*   *   *   *   *"
  addJob (pushCalendarUpdatesToOffice365 app)  "*/5 *   *   *   *"
pushLogStr (loggerSet $ appLogger app) $ "All cronjobs have been scheduled"

For some reason (that I'm still looking into), these don't parse correctly. However, my concern is not just about the failure to parse but about what happens after a failure. I see the following stdout when I run this:

ParseError "Failed reading: takeWhile1"
All cronjobs have been scheduled

So, execSchedule doesn't throw an exception in IO when something goes wrong, and I think that it would be better behavior if it did. This would make it more likely that people (cough cough... me) would discover mistakes at load time. Let me know what you think of this.

Is this repo still maintained?

Hi,

Thank you for this library, we currently use it in my team and it works like a charm 😄

I was wondering if this library is still maintained? Reasons why I ask:

Build is failed on the badge (https://travis-ci.org/MichaelXavier/cron)
Latest Hackage upload was on November 2017 while there were several commits since
cron is not included in the next Stackage release (as is), I suspect because of the repeated build failures caused by MonadFail changes (which is a shame since I see a commit to fix this very issue in October 2019)

I hope this issue/question doesn't appear as rude 😅 I want to know if we need to fork it, or find an alternative (I did not find one yet), in anticipation of the next major GHC release 8.8 on Stack.

Cheers!

Test suite failure

      returns the first minute in the future that matches:               FAIL (8.09s)
        *** Failed! (after 19 tests and 1 shrink): 
        Exception:
          test/System/Test/Cron.hs:276:15-92: Irrefutable pattern failed for pattern Just actual
        CronSchedule * * * * *
        1858-11-17 13:50:59.579131947983 UTC
        Exception thrown while printing test case:
          test/System/Test/Cron.hs:276:15-92: Irrefutable pattern failed for pattern Just actual

        Use --quickcheck-replay '90 TFGenR 00000010C895C77300000000000F4240000000000000E0BC00000001FB8896C0 0 536869888 29 0' to reproduce.
      a schedule that produces Just for one t will produce it for any t: OK (0.11s)
        +++ OK, passed 100 tests.

fails to build in ghc-9.6 stackage nightly

       Building library for cron-0.7.0..                                                                                [282/157179]
       [10 of 12] Compiling System.Cron.Schedule                                                                                    
                                                                                                                                    
       /var/stackage/work/unpack-dir/unpacked/cron-0.7.0-a644a72eef6377a56613b423ddc438ab324361759876a64cec8ed479374a36ff/src/System
/Cron/Schedule.hs:142:30: error: [GHC-88464]
           Variable not in scope: forever :: IO b0 -> IO ()                                                                         
           |                     
       142 | forkJob (Job s a) = forkIO $ forever $ do                                                                              
           |                              ^^^^^^^                                                                                   
                                 
       /var/stackage/work/unpack-dir/unpacked/cron-0.7.0-a644a72eef6377a56613b423ddc438ab324361759876a64cec8ed479374a36ff/src/System
/Cron/Schedule.hs:145:13: error: [GHC-88464]
           Variable not in scope: when :: Bool -> t0 -> IO b0                                                                       
           |                     
       145 |             when (scheduleMatches s timeAt) (void $ forkIO a)
           |             ^^^^
                                 
       /var/stackage/work/unpack-dir/unpacked/cron-0.7.0-a644a72eef6377a56613b423ddc438ab324361759876a64cec8ed479374a36ff/src/System
/Cron/Schedule.hs:145:46: error: [GHC-88464]
           Variable not in scope: void :: IO ThreadId -> t0                                                                         
           |                     
       145 |             when (scheduleMatches s timeAt) (void $ forkIO a)
           |                                              ^^^^

Incorrect timing for combinations of StepField and RangeField

When you do this:

1-59/2 * * * *

it treats it as though you did this

*/2 * * * *

please add method to calculate the next time when a crontab is expected to match

I'd like to build a tool that checks, whether all my crontabs did run as expected. For this I need to know, when a crontab is actually expected to run after a given timestamp.

System.Cron.Describe does not accept time zone settings

I'd like to display the cron description in the local timezone. So,

At 02:00 AM, every 3 days

would be (in my time zone, settable w/ the opts monoid)

At 09:00 PM, every 3 days

Also, being able to remove the leading zeros would be nice (in the hours component)

Error compiling with GHC 7.10

[3 of 3] Compiling System.Cron.Schedule ( src/System/Cron/Schedule.hs, dist/build/System/Cron/Schedule.o )

src/System/Cron/Schedule.hs:109:32:
    Ambiguous occurrence ‘defaultTimeLocale’
    It could refer to either ‘Data.Time.defaultTimeLocale’,
                             imported from ‘Data.Time’ at src/System/Cron/Schedule.hs:53:1-26
                             (and originally defined in ‘time-1.5.0.1:Data.Time.Format.Locale’)
                          or ‘System.Locale.defaultTimeLocale’,
                             imported from ‘System.Locale’ at src/System/Cron/Schedule.hs:56:1-30

src/System/Cron/Schedule.hs:110:39:
    Ambiguous occurrence ‘defaultTimeLocale’
    It could refer to either ‘Data.Time.defaultTimeLocale’,
                             imported from ‘Data.Time’ at src/System/Cron/Schedule.hs:53:1-26
                             (and originally defined in ‘time-1.5.0.1:Data.Time.Format.Locale’)
                          or ‘System.Locale.defaultTimeLocale’,
                             imported from ‘System.Locale’ at src/System/Cron/Schedule.hs:56:1-30

src/System/Cron/Schedule.hs:112:30:
    Ambiguous occurrence ‘defaultTimeLocale’
    It could refer to either ‘Data.Time.defaultTimeLocale’,
                             imported from ‘Data.Time’ at src/System/Cron/Schedule.hs:53:1-26
                             (and originally defined in ‘time-1.5.0.1:Data.Time.Format.Locale’)
                          or ‘System.Locale.defaultTimeLocale’,
                             imported from ‘System.Locale’ at src/System/Cron/Schedule.hs:56:1-30

I think this is related to https://ghc.haskell.org/trac/ghc/wiki/Migration/7.10?version=9#time-1.5.0.1

Surviving exceptions

See my PR
#19

Cron job is sometimes triggered twice in a row

Hello

First of all, thank you for this very useful library I recently started to work with.

I am experiencing some troubles when scheduling a simple job to start every minutes as it sometimes starts two threads within the same second.

ThreadId 20 at 2019-12-13 13:37:59.999691 UTC
ThreadId 21 at 2019-12-13 13:38:00.001119 UTC

I tried to reproduce in a standalone / simple example which is the following:

module Example where

import           Control.Concurrent (myThreadId)
import           Data.Time          (getCurrentTime)
import           System.Cron

runApplication :: IO ()
runApplication = do
  threadIds <- execSchedule setupCronJob
  putStrLn $ "Scheduling job " <> show threadIds <> " is running"
  _ <- getLine
  -- to stop only when the user types
  pure ()

setupCronJob :: Schedule ()
setupCronJob = addJob runJob "* * * * *"

runJob :: IO ()
runJob = do
  threadId <- myThreadId
  currentTime <- getCurrentTime
  putStrLn $ show threadId <> " at " <> show currentTime

This example triggers a job which prints the threadId with the current execution time and I get the following output:

Scheduling job [ThreadId 12] is running
ThreadId 13 at 2019-12-13 13:31:00.004439 UTC
ThreadId 14 at 2019-12-13 13:32:00.003727 UTC
ThreadId 15 at 2019-12-13 13:33:00.003082 UTC
ThreadId 16 at 2019-12-13 13:34:00.000189 UTC
ThreadId 17 at 2019-12-13 13:35:00.001204 UTC
ThreadId 18 at 2019-12-13 13:36:00.002054 UTC
ThreadId 19 at 2019-12-13 13:37:00.001719 UTC
ThreadId 20 at 2019-12-13 13:37:59.999691 UTC
ThreadId 21 at 2019-12-13 13:38:00.001119 UTC
ThreadId 22 at 2019-12-13 13:39:00.003116 UTC
ThreadId 23 at 2019-12-13 13:40:00.00399 UTC
ThreadId 24 at 2019-12-13 13:41:00.00291 UTC
ThreadId 25 at 2019-12-13 13:42:00.001187 UTC
ThreadId 26 at 2019-12-13 13:43:00.002664 UTC

I sometimes need to wait around 10 minutes to get this error.

I experience this issue in a MacOs Mojave as another colleague of mine but others don't get it in a Linux based OS.

Did anybody experienced the same behavior or do you have any hint to help on this topic?

Thank you in advance!

Support for mtl 2.2?

Would it be possible to get a version of this package that supports recent releases of mtl: http://packdeps.haskellers.com/feed?needle=cron-compat? Maybe
http://hackage.haskell.org/package/mtl-compat can help achieve that?

The leap second caused a scheduled job to run twice

I have a job that is scheduled to run at 0 0 1 * *, i.e. at midnight at the beginning of each month. This worked as expected until this past January 1, when the job ran twice. PostgreSQL reports that the task ran at the following times:

2016-12-31 23:59:59.070603+00
2017-01-01 00:00:00.006794+00

For comparison, the most recent normal run happened at 2016-12-01 00:00:00.006968+00.

I assume that the culprit was the leap second that was inserted at the end of 2016-12-31: there was a 23:59:60 on that day.

This happened under Ubuntu 14.04.5. The machine uses NTP (with, I believe, whatever the default Ubuntu configuration is) to keep its time in sync.

Interpreting the schedule in a certain time zone

My server is set to UTC. I have a haskell-cron application that should interpret its times in U.S. Eastern Standard Time (UTC-5) instead—for example, 0 0 * * * would specify a task that should run daily at 5:00 AM UTC. Is there a straightforward way to do this?

(I tried playing around in GHCi with the TZ environment variable set to US/Eastern, but the times were still interpreted in UTC.)

[Idea] Non-overlapping cron jobs

Hi!

It would be nice for a library to have a flag for non-overlapping jobs where frequently triggered jobs are not triggered again if one of the previously started jobs hasn't finished yet. This is useful in data processing flows where processing actions take longer than the scheduled "timeout".

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