[wp-trac] [WordPress Trac] #41098: Some cron scheduling events are ignored

[WordPress Trac]

#41098: Some cron scheduling events are ignored
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 Reporter:  bor0          |      Owner:
     Type:  defect (bug)  |     Status:  new
 Priority:  normal        |  Milestone:  Awaiting Review
Component:  Cron API      |    Version:  trunk
 Severity:  normal        |   Keywords:
  Focuses:                |
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 The problem appears when two different events are scheduled at the same
 time.

 It's a bit hard to reproduce, but if one plugin is continuously scheduling
 events (e.g. recurrent schedule every 5 mins, but they execute for 5
 mins), another plugin's scheduling events might be completely ignored.

 I believe this is because there is no lock mechanism in the schedule
 functions where we write to the `cron` option in the database.

 What happens in the code is:

 Continuous (plugin #1): wp-cron.php has `wp_unschedule_event` in a loop
 (which may overwrite `cron` option in the database)

 Random (plugin #2): Call `wp_schedule_event` to update `cron` option, but
 plugin #1 may have overwritten it already.

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Ticket URL: <https://core.trac.wordpress.org/ticket/41098>
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