public function update()
    {
        $now = new \DateTime();

        foreach ($this->toUpdate as $providerName => $urls) {
            foreach ($urls as $url) {
                $shares = $this->providers[$providerName]['provider']->getShares($url);

                $this->cache->save($this->getId($providerName, $url), array($shares, $now));
            }
        }
    }