First draft at hook to control wp-cron.php endpoint.

[peterwilsoncc]

• Introduces a filter to allow developers to enable/disable the wp-cron.php endpoint, wp_cron_endpoint_enabled.
• The default value of the constant DISABLE_WP_CRON is defined and set to false if the endpoint is disabled.
• Modifies wp-cron.php endpoint:
  • Adds a header indicating whether jobs are spawned or bypassed
  • Modifies when the request fast-finishes running to allow said header to be sent.

Trac ticket: https://core.trac.wordpress.org/ticket/64157

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[westonruter]

Instead of a custom header, what about:

Suggested change

	header( 'X-WP-Cron: Bypass' );
	status_header( 403 );

[peterwilsoncc]

I'm happy to do this if batcache caches 403 responses (pending adding output to the page, as discussed on the ticket).

[westonruter]

Can't these headers be left right here? They're now sent in two different places below.

[peterwilsoncc]

There's a slight change: if requests are bypassed the no-caching headers aren't sent as it's safe to cache the endpoint as it doesn't need to hit the database.

[westonruter]

Ah, right. Good point

[westonruter]

This would seem like a good place to send status_header( 400 ). I'm not sure when this ! empty( $_POST ) || defined( 'DOING_AJAX' ) || defined( 'DOING_CRON' ) condition would happen normally.

[westonruter]

Instead of sending this here, what if below where it does:

if ( empty( $crons ) ) {
	die();
}

It could be changed to:

if ( empty( $crons ) ) {
	status_header( 304 );
	die();
} else {
	status_header( 200 );
}

[peterwilsoncc]

I'm unsure. It's still a successful request if the cron array is empty, it just happens that there are no jobs to spawn. It would also require the DB request be made before the fast finish.