ZDB Linked Data Service: Suspicious Multiple Requests

[thoffma]

Hi!
We (German National Library) were alerted by our system that we recieve unusual many (multiple) requests from different ip adresses who are all using the agent "TYPO3". After some mail contact with different institutions we suspect the modul libconnect to be the troublemaker.

The requests looks like this:

"GET /data/1468190-0.rdf HTTP/1.1" 200 5758 "
"GET /data/1468190-0.rdf HTTP/1.1" 200 5758 "
"GET /data/2220742-9.rdf HTTP/1.1" 200 5198 "
"GET /data/2220742-9.rdf HTTP/1.1" 200 5198 "

and so on...
We can not say since when this started.

Do you have an idea what could be the issue? Could it be an issue inside libconnect?

Thanks
Tracy (DNB)

[gjaekel]

Seems to be a duplicate of #18.

In getTitleHistory

libconnect/Classes/Domain/Repository/EzbRepository.php

Lines 709 to 722 in 3691c69

	private function getTitleHistory($zdbId)
	{
	$precursor = $this->zdb->getPrecursor($zdbId, true);
	krsort($precursor);
	$successor = $this->zdb->getSuccessor($zdbId);
	if ((empty($precursor)) && (empty($successor))) {
	return false;
	}
	return ['precursor' => $precursor, 'zdbData' => $this->zdb->getZdbData(), 'successor' => $successor];
	}

there's a call to getPrecursor and getSuccessor:

libconnect/Classes/Lib/Zdb.php

Lines 344 to 349 in 93aea90

	public function getPrecursor($zdbId, $initial = false)
	{
	//example "https://ld.zdb-services.de/data/2890450-3.rdf";
	$url = 'https://ld.zdb-services.de/data/' . $zdbId . '.rdf';
	$request = $this->setRequest($url);

libconnect/Classes/Lib/Zdb.php

Lines 437 to 441 in 93aea90

	public function getSuccessor($zdbId)
	{
	$url = 'https://ld.zdb-services.de/data/' . $zdbId . '.rdf';
	$request = $this->setRequest($url);

This both methods did a HTTP-request to the Backend ld.zdb-services.de in any case; that's the reason for a double call.

To avoid this, the result of a call to a identical backend URL might be cached and reused.