[wp-trac] [WordPress Trac] #42660: Single event scheduler

[WordPress Trac]

#42660: Single event scheduler
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 Reporter:  skarabeq           |       Owner:
     Type:  defect (bug)       |      Status:  closed
 Priority:  normal             |   Milestone:
Component:  Cron API           |     Version:  4.9
 Severity:  normal             |  Resolution:  invalid
 Keywords:  reporter-feedback  |     Focuses:
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Changes (by dd32):

 * status:  new => closed
 * resolution:   => invalid
 * severity:  major => normal
 * milestone:  Awaiting Review =>


Comment:

 Replying to [comment:10 skarabeq]:
 > @ocean90 with this code:
 >
 > {{{#!php
 > <?php
 > if ( ! wp_next_scheduled( 'single_action' ) ) {
 >         wp_schedule_single_event( strtotime( '2017-11-22 11:00' ),
 'single_action' );
 > }
 > }}}
 >
 > isn't works like as expect. Still triggered event on every refresh on
 website (doesn't matter where I'm)

 I think what is happening here is:
 - Pageload 1: See's there's no `single_action` scheduled, so queues it up.
 Later in the pageload it sees there's crons that need running, so it
 spawns the cron process.
  - Cron pageload runs in background. removes cron entry.
 - Pagelaod 2: The cron run has already processed the cron and removed its
 entry from the database, so `wp_next_scheduled( 'single_action' )` is once
 again `false`, so it queues it up again to run
   - Cron pageload runs in the background again
 rinse repeat.

 In your case, you should -conditionally- call `wp_schedule_single_event()`
 when a certain circumstance is true (For example, `if ( isset( $_POST
 ['schedule-the-cron'] ) ) { wp_schedule_single_event( time(),
 'single_action' ); }`).

 This is a hastily written, and insecure, but here's an example plugin
 which shows an implementation where the cron only fires once, in response
 to a user action triggering it to run:
 https://gist.github.com/dd32/d1091e4f6316dba126814b5d3ce559bb

 I hope this helps set you on the right direction.
 I'm marking this ticket as invalid as there's nothing which can be used to
 point to a core bug, discussion can still occur while the ticket is
 closed, please do not re-open the ticket unless you have information which
 can be used to reproduce a bug in core.

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Ticket URL: <https://core.trac.wordpress.org/ticket/42660#comment:12>
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