wp-network-cron.php

<?php

require( 'wp-load.php' ); // Make sure to set the correct path to wp-load.php file

set_time_limit( 300 ); // Optional, yet might be necessary depending on the server configuration

// BEGIN Configuration
$admin_email = 'email@example.com';
$max_log_size_bytes = 1024 * 1024; // 1 MB
$log_file = '/home/user/multisite-cron.log';
$timestamp = date( 'Y-m-d H:i:s' );
$sleep_time = 3;
// END Configuration

$errors = [];

file_put_contents( $log_file, "\n\n[$timestamp] Starting WP Multisite cron execution\n", FILE_APPEND );

if ( is_multisite() ) {
	$sites = get_sites();

	foreach ( $sites as $site ) {
		$site_url = get_site_url( $site->blog_id );
		$command  = $site_url . '/wp-cron.php?doing_wp_cron';

		// Optional: switch_to_blog for future use
		//switch_to_blog( $site->blog_id );
		//wp_suspend_cache_addition( true );

		$response = wp_remote_get( $command, [
			'timeout'  => 15,
			'blocking' => false,
		] );

		if ( is_wp_error( $response ) ) {
			$error_message = $response->get_error_message();
			$errors[] = "[$timestamp] [ERROR] {$site_url}: $error_message";
			file_put_contents( $log_file, end($errors) . "\n", FILE_APPEND );
		} else {
			file_put_contents( $log_file, "[$timestamp] [OK] Triggered cron for {$site_url}\n", FILE_APPEND );
		}

		// Optional: switch_to_blog for future use
		//wp_suspend_cache_addition( false );
		//restore_current_blog();

		sleep( $sleep_time );
	}
}

file_put_contents( $log_file, "[$timestamp] Finished WP Multisite cron execution\n", FILE_APPEND );

// Email alert on failures
if ( ! empty( $errors ) ) {
	$subject = 'WP Multisite Cron Failures';
	$body = "Some WP Cron requests failed:\n\n" . implode( "\n", $errors );
	wp_mail( $admin_email, $subject, $body );
}

// Email alert on log size
$log_size = file_exists( $log_file ) ? filesize( $log_file ) : 0;

if ( $log_size >= $max_log_size_bytes ) {
	$subject = 'WP Multisite Cron Log Size Warning';
	$body = "The cron log file has reached " . round( $log_size / 1024, 2 ) . " KB.\n\nConsider rotating or cleaning the log:\n{$log_file}";
	wp_mail( $admin_email, $subject, $body );
}