Run a cron job (or similar) in the background of WP after post update/create

3 comments

1. Alright, here’s some code I just whipped up. Completely untested, just wrote it right off the cuff…so don’t expect it to work 100% when you drop it in, but the core concept is there, as is a decent amount of the legwork

   add_action( 'my_filter_posts_content', 'my_filter_content' );
   add_action( 'save_post', 'my_set_content_filter' );
   
   if( !wp_next_scheduled( 'my_filter_posts_content' ) ) {
       wp_schedule_event( time(), 'hourly', 'my_filter_posts_content' );
   }
   
   function my_filter_content() {
       //check to see if posts need to be parsed
       if( get_option( 'my_updated_posts' ) == false )
           return false;
   
       //parse posts
       $ids = unserialize( get_option( 'my_updated_posts' ) );
       foreach( $ids as $v ) {
           YOUR_FUNCTION_HERE( $v );
       }
   
       //make sure no values have been added while loop was running
       $id_recheck = unserialize( get_option( 'my_updated_posts' ) );
       my_close_out_filter( $ids, $id_recheck );
   
       /*
       once all options, including any added during the running of what
       could be a long cronjob are done, remove the value and close out
       */
       delete_option( 'my_updated_posts' );
       return true;
   }
   
   function my_set_content_filter( $post_id ) {
       //get the previous value
       $ids = unserialize( get_option( 'my_updated_posts' ) );
   
       //add new value if necessary
       if( !in_array( $post_id, $ids ) ) {
           $ids[] = $post_id;
           update_option( 'my_updated_posts', serialize( $ids ) );
       }
   }
   
   function my_close_out_filter( $beginning_array, $end_array ) {
       $diff = array_diff( $beginning_array, $end_array );
       if( !empty ( $diff ) ) {
           foreach( $diff as $v ) {
               YOUR_FUNCTION_HERE( $v );
           }
       }
       my_close_out_filter( $end_array, unserialize( get_option( 'my_updated_posts' ) ) );
   }
   

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2. Please see my answer here. It’s a proof-of-concept for running a native crontab in Linux with your WP installation.

   As for WP-Cron functionality, beware of these caveats:

   • WP-Cron is a pseudo cron that is runs when WP is loaded. WP checks if a WP-Cron is scheduled or behind schedule to run and then executes the cron script.
   • If there is not adequate traffic, your cron might run really late.
   • Scheduling a WP-Cron to run during peak hours might cause some performance issues if it’s a large, intensive script.

   If you choose to go the WP-Cron route, here’s a great article to show you how to use it. You can also check out the WP functions in the Codex here.

   I prefer the reliability of a Linux crontab, especially for integral, heavy-weight cron scripts. For extremely lightweight scripts, I do use WP-Cron at times.

   Hope this helps!

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3. Would the save_post action work for you?

   <?php
   add_action( 'save_post', 'wp_save_post' );
   function wp_save_post()
   {
       // do stuff
   }
   

   You might also consider edit_post or publish_post

   You can view other actions in the Codex

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