Pubjet | پاب‌جت

On payamema.ir, this plugin caused repeated MySQL lock contention and service outages.

Root cause:

• Cron jobs are registered on every frontend request via:

  add_action('wp', [$this, 'registerCron'], 15);

• Even with wp_next_scheduled() and a short-lived transient lock, concurrent requests (users + wp-cron + wp-cli) race and repeatedly call wp_schedule_event().

Impact:

• The wp_options.cron option grows very large.
• Multiple simultaneous UPDATE wp_options SET option_value = ... WHERE option_name='cron'
• InnoDB row-level lock contention on wp_options
• Dozens of queries stuck in updating / waiting for handler commit
• High MySQL memory usage → site slowdown / downtime

Evidence:

• Hundreds of duplicated timestamps for pubjet_schedule_delete_logs in the cron option.
• MySQL processlist showing ~50 concurrent updating queries on wp_options.

Correct fix:

• Cron jobs must be registered only on plugin activation, not on every request.
• registerCron() should be called via register_activation_hook()
• Runtime cron registration on wp is not production-safe.

This issue directly caused database locks and outages on a live news website.

سلام

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