gistfile1.php

	/**
	 * Acquires an indexing lock if possible.
	 *
	 * @return boolean
	 */
	private function acquireLock()
	{
		$redis = $this->getRedis();

		if ($redis->setNX(self::LOCK_KEY, $this->getTimeout())) {
			return true;
		}

		$redis->watch(self::LOCK_KEY);

		$lockExpiration = $redis->get(self::LOCK_KEY);
		if ($lockExpiration < time()) {
			try {
				$redis->multi();
				$this->updateLockTimeout();
				$redis->exec();

				return true;
			} catch (Predis\Transaction\AbortedMultiExecException $e) {
				return false;
			}
		}

		$redis->unwatch();
		return false;
	} 

	/**
	 * Updates the indexing lock timeout.
	 */
	private function updateLockTimeout()
	{
		$this->getRedis()->set(self::LOCK_KEY, $this->getTimeout());
	}