Checking the activity of subsites

Regarding WP subsites, usage stats can be compiled. If you cannot find a plugin to help you do this, it may need to be custom coded, but it is possible.

Regarding server resources, I’m not 100% sure but likely no, because all traffic is routed through the one WP installation. You could ask your host for confirmation to be certain.

Here is a custom starter plugin that shows CPU, RAM, WordPress Installation size, and Last login date/time:

<?php
/**
 * Plugin Name: Subsite Info Dashboard Widget
 * Plugin URI: https://www.deviant.media
 * Description: Adds a dashboard widget that displays subsite information.
 * Version: 1.0
 * Author: Albert Bretado
 * Author URI: https://www.deviant.media
 */

if (!function_exists('get_dirsize')) {
  function get_dirsize($dir) {
    $size = 0;
    $it = new RecursiveIteratorIterator(new RecursiveDirectoryIterator($dir));
    while ($it->valid()) {
      if (!$it->isDot()) {
        $size += $it->getSize();
      }
      $it->next();
    }
    return $size;
  }
}

function system_info_dashboard_widget() {
  global $wpdb;
  
  $blogs = $wpdb->get_results("SELECT blog_id FROM {$wpdb->blogs}", ARRAY_A);
  
  foreach ($blogs as $blog) {
    switch_to_blog($blog['blog_id']);
    
    $load = sys_getloadavg();
    $cpu = round($load[0], 2);
    $ram = round((memory_get_usage() / 1024 / 1024), 2);
    
    $wordpress_dir = ABSPATH;
    $wordpress_size = round((get_dirsize($wordpress_dir) / 1024 / 1024), 2);
    
    $last_login = '';
    $admins = get_users(array('role' => 'administrator'));
    foreach ($admins as $admin) {
      $last_login_timestamp = get_user_meta($admin->ID, 'last_login', true);
      if ($last_login_timestamp !== '') {
        $last_login = date('Y-m-d H:i:s', $last_login_timestamp);
        break;
      }
    }
    if ($last_login == '') {
      $last_login = 'N/A';
    }
    ?>
    <div class="system-info">
      <h2><?php echo get_bloginfo('name'); ?></h2>
      <p><strong>CPU Usage:</strong> <?php echo $cpu; ?>%</p>
      <p><strong>RAM Usage:</strong> <?php echo $ram; ?> MB</p>
      <p><strong>WordPress Size:</strong> <?php echo $wordpress_size; ?>MB</p>
      <p><strong>Last Login:</strong> <?php echo $last_login; ?></p>
    </div>
    <?php
    restore_current_blog();
  }
}

function set_last_login($user_login) {
  $user = get_user_by('login', $user_login);
  $user_id = $user->ID;
  update_user_meta($user_id, 'last_login', current_time('timestamp'));
}

function add_system_info_dashboard_widget() {
  if (is_network_admin()) {
    wp_add_dashboard_widget('system_info_dashboard_widget', 'System Info', 'system_info_dashboard_widget');
  }
}
add_action('wp_login', 'set_last_login', 10, 2);
add_action('wp_network_dashboard_setup', 'add_system_info_dashboard_widget');

Feel free to adjust as you see fit.

@abretado1985

Thank you very much for this.
The last login works but the resource usages give the same value for each site. For example, all sub-sites appear as 500 mb, and I think these resource usages are the main site’s resource usage.

@bcworkz

Thank you for your reply. Do you know of a plugin for this?

You could try some of these plugins. I’m not that confident their stats are broken out by subsite.