controls-web/data/latency-monitor.php

<?php // phpcs:ignoreFile

require __DIR__ . '/../includes/db.php';

$appTimeZone = new DateTimeZone('America/Chicago');
$errorMessage = null;
$devices = [];

try {
    $connection = controls_db_connect();
} catch (Throwable $exception) {
    $connection = null;
    $errorMessage = $exception->getMessage();
}

if ($connection instanceof mysqli) {
    $sql = <<<SQL
SELECT d.id,
       d.host,
       d.label,
       latest.status,
       latest.latency_ms,
       latest.checked_at
FROM monitoring_devices AS d
LEFT JOIN (
    SELECT l1.device_id,
           l1.status,
           l1.latency_ms,
           l1.checked_at
    FROM monitoring_latency_log AS l1
    INNER JOIN (
        SELECT device_id, MAX(checked_at) AS max_checked
        FROM monitoring_latency_log
        GROUP BY device_id
    ) AS recent ON recent.device_id = l1.device_id AND recent.max_checked = l1.checked_at
) AS latest ON latest.device_id = d.id
WHERE d.is_active = 1
ORDER BY d.label;
SQL;

    try {
        $result = $connection->query($sql);
        if ($result instanceof mysqli_result) {
            while ($row = $result->fetch_assoc()) {
                if (!empty($row['checked_at'])) {
                    $timestamp = DateTimeImmutable::createFromFormat(
                        'Y-m-d H:i:s',
                        $row['checked_at'],
                        new DateTimeZone('UTC')
                    );
                    if ($timestamp instanceof DateTimeImmutable) {
                        $timestamp = $timestamp->setTimezone($appTimeZone);
                        $row['checked_at_formatted'] = $timestamp->format('M j, Y g:i:s A T');
                    }
                }

                $devices[] = $row;
            }
            $result->free();
        }
    } catch (Throwable $exception) {
        $errorMessage = $exception->getMessage();
    } finally {
        $connection->close();
    }
}

ob_start();
?>

<header class="panel-header">
  <h2>Device latency status</h2>
  <p>Latest response times collected by the latency watcher service.</p>
</header>

<?php if (!empty($errorMessage ?? null)) : ?>
  <div class="panel-error">
    <strong>Unable to load data:</strong>
    <span><?php echo htmlspecialchars($errorMessage); ?></span>
  </div>
<?php elseif (empty($devices)) : ?>
  <div class="panel-loading">
    <span>No latency samples have been recorded yet.</span>
    <span>Verify the watcher is running and devices are configured.</span>
  </div>
<?php else : ?>
  <div class="latency-table-wrapper">
    <table class="latency-table">
      <thead>
        <tr>
          <th scope="col">Device</th>
          <th scope="col">Host</th>
          <th scope="col">Status</th>
          <th scope="col">Latency (ms)</th>
          <th scope="col">Last checked</th>
        </tr>
      </thead>
      <tbody>
        <?php foreach ($devices as $device) : ?>
          <?php
            $status = $device['status'] ?? null;
            $latency = $device['latency_ms'] ?? null;
            $statusLabel = 'Unknown';
            $statusClass = 'status-pill--unknown';

            $trendUrl = 'trends/live/autochart.php?'
                . http_build_query([
                    'primary' => 'latency:' . $device['id'],
                    'primary_label' => $device['label'],
                    'autostart' => '1',
                    'interval' => '5000',
                ]);

            if ($status === 'up') {
                $statusLabel = 'Online';
                $statusClass = 'status-pill--up';
            } elseif ($status === 'down') {
                $statusLabel = 'Offline';
                $statusClass = 'status-pill--down';
            }
          ?>
          <tr>
            <td data-label="Device">
              <a class="latency-link" href="<?php echo htmlspecialchars($trendUrl, ENT_QUOTES, 'UTF-8'); ?>" target="_blank" rel="noopener">
                <?php echo htmlspecialchars($device['label']); ?>
              </a>
            </td>
            <td data-label="Host"><?php echo htmlspecialchars($device['host']); ?></td>
            <td data-label="Status">
              <span class="status-pill <?php echo $statusClass; ?>">
                <?php echo htmlspecialchars($statusLabel); ?>
              </span>
            </td>
            <td data-label="Latency">
              <?php echo $latency !== null ? number_format((float) $latency, 0) : '—'; ?>
            </td>
            <td data-label="Last checked">
              <?php echo htmlspecialchars($device['checked_at_formatted'] ?? '—'); ?>
            </td>
          </tr>
        <?php endforeach; ?>
      </tbody>
    </table>
  </div>
<?php endif; ?>

<footer class="latency-footnote">
  <p>
    Results update whenever <code>monitoring/latency_watcher.py</code> records a sample.
    Configure devices in the <code>monitoring_devices</code> table and ensure the watcher
    has database access.
  </p>
</footer>

<?php
$payload = ob_get_clean();
$etag = '"' . md5($payload) . '"';
$clientEtag = isset($_SERVER['HTTP_IF_NONE_MATCH']) ? trim($_SERVER['HTTP_IF_NONE_MATCH']) : null;

if ($clientEtag && $clientEtag === $etag) {
    header('HTTP/1.1 304 Not Modified');
    header('Cache-Control: no-cache, must-revalidate');
    header('ETag: ' . $etag);
    exit;
}

header('Cache-Control: no-cache, must-revalidate');
header('Content-Type: text/html; charset=utf-8');
header('ETag: ' . $etag);

echo $payload;