private function findWorkerTenderProcessesForTube($tube)
    {
        $processes = array();
        $command = "ps ax ";
        $command .= "|grep php ";
        $command .= "|grep -v stop ";
        $command .= "|grep worker-tender ";
        if ($tube !== '') {
            $command .= "|grep " . escapeshellarg('use-tube=' . $tube);
        }
        $data = exec($command);
        $lines = explode("\n", $data);
        foreach ($lines as $line) {
            $line = trim($line);
            $parts = explode(" ", $line);
            if ($parts[0] === '') {
                continue;
            }
            $processes[] = intval($parts[0]);
        }

        return $processes;

    }