[wp-trac] [WordPress Trac] #51747: wp_schedule_event fails if cron job is unfortunately running.

[WordPress Trac]

#51747: wp_schedule_event fails if cron job is unfortunately running.
------------------------------+-----------------------------
 Reporter:  Takahashi_Fumiki  |      Owner:  (none)
     Type:  enhancement       |     Status:  new
 Priority:  normal            |  Milestone:  Awaiting Review
Component:  Cron API          |    Version:  trunk
 Severity:  normal            |   Keywords:  needs-patch
  Focuses:  performance       |
------------------------------+-----------------------------
 Some feature(e.g. scheduled posts) requires `cron` parameter to be stored
 in `wp_options` as single array.
 But if wp cron job is running, this array may be overridden.
 Writing in an easier format...

 {{{
 //wp-cron.php recognize cron jobs like below.
 [
  'a',
  'b',
  'c',
  'z'
 ]
 //
 foreach( $jobs as $job ) {
   // Oh, c should be done.
   // Reschedule or unschedule events.
   wp_reschedule_event( $job->event_name, $job->args );
   // Execute.
   $job->exec();
 }
 // Result corn jobs.
 [
  'a',
  'b',
  'z',
 ]
 }}}

 If someone tries scheduling a new event simultaneously, it fails.

 {{{
 // Si
 // in wp-admin/edit.php or /wp-json/wp/v2/posts
 // with wp_insert_post or something,
 // expected cron jobs.
 [
   'a',
   'b',
   'c',
   'please_publish_my_new_post',
   'z,'
 ]
 }}}

 In this case, the actual result will be...

 {{{
 [
  'a',
  'b',
  'z'
 ]
 }}}

 Thus, the `please_publish_my_new_post` hook never happens, and the post
 will be marked as `Missed schedule`.

 == How to reproduce

 I made a plugin to reproduce this. https://github.com/kuno1/nabeatsu-of-
 the-world

 [[Image(https://raw.githubusercontent.com/kuno1/nabeatsu-of-the-
 world/main/screenshot.png)]]

 This plugin will:

 - Register WP-Cron job runs every minute. The job sometimes take very long
 time(40 sec) for execution.
 - On front end, schedule new post in every 10 seconds.
 - You will get 360 scheduled posts in 1 hour and each of them should be
 published in 5 minutes from their creation.
 - But some of them are "Missed schedule"

 == Solution

 - Scheduling and execution should be split. Scheduling matters.

 I'm working on a new patch.

 == Note

 - In some ticket( e.g. #49520, #15148 ), changing cron storage approach.
 - This frequently occurs in large sites which hold by many writers and
 posted many articles.
 - Some core jobs(e.g. removing old transients, empty trash) may also
 increase the probability.
 - Site with many customers with recurring payment(e.g. ) also have high
 probability.

-- 
Ticket URL: <https://core.trac.wordpress.org/ticket/51747>
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