protected function addHistory($sEvent, $sNamespace = 'nails/common')
    {
        $sEvent     = strtoupper($sEvent);
        $sNamespace = strtoupper($sNamespace);

        if (!array_key_exists($sNamespace, $this->aHistory)) {
            $this->aHistory[$sNamespace] = [];
        }
        if (!array_key_exists($sEvent, $this->aHistory[$sNamespace])) {
            $this->aHistory[$sNamespace][$sEvent] = (object) [
                'count'      => 0,
                'timestamps' => [],
            ];
        }

        $this->aHistory[$sNamespace][$sEvent]->count++;
        $this->aHistory[$sNamespace][$sEvent]->timestamps[] = microtime(true);
        return $this;
    }