[tdwg-tag] LSIDs: web based (HTTP) resolvers and web crawlers

Roderic Page r.page at bio.gla.ac.uk
Mon Apr 27 15:30:02 CEST 2009 

Dear Nicky,

Ouch!

I'm not sure I fully understand how 30* redirects work with respect to  
web crawlers, but I'm not sure they will help in this case.

If the TDWG LSID resolver is a full blown resolver, then for each  
request from the crawler it will be doing the full LSID resolution  
(three calls, one for authority WSDL, one for service WSDL, one for  
metadata). It may cache the WSDLs, but it will still do at least one  
call to the service (unless it has cached the metadata as well).

Is the solution to add TDWG to your robots.txt file, and have the LSID  
resolver respect the settings in that file? TDWG could also implement  
metadata caching so it wouldn't need to hammer you so much (i.e., when  
a crawler hit TDWG, TDWG would reply with the cached metadata).

Perhaps LSID services such as IPNI's could also implement etag  
headers, which would help avoid excessive traffic from TDWG when  
caching (TDWG could regularly cache metadata form IPNI, respecting the  
robots.txt files, and first checking whether the metadata had changed  
using etag and/or last modified headers).

I assume the DOI resolve has similar issues. It's robots.txt file  
looks like this:

Crawl-delay: 5
Request-rate: 1/5


Hope this makes sense, my understanding of the HTTP headers/redirects/ 
robots.txt is not particularly deep.

Regards

Rod




On 27 Apr 2009, at 13:54, Nicola Nicolson wrote:

> Hi,
>
> Further to my last design question re LSID HTTP proxies (thanks for  
> the responses), I wanted to raise the issue of HTTP LSID proxies and  
> crawlers, in particular the crawl delay part of the robots exclusion  
> protocol.
>
> I'll outline a situation we had recently:
>
> The GBIF portal and ZipCodeZoo site both inclde IPNI LSIDs in the  
> pages. These are presented in their proxied form using the TDWG LSID  
> resolver (eg http://lsid.tdwg.org/urn:lsid:ipni.org:names:783030-1).  
> Using the TDWG resolver to access the data for an IPNI LSID does not  
> issue any kind of HTTP redirect, instead the web resolver uses the  
> LSID resolution steps to get the data and presents it in its own  
> response (ie returning a HTTP 200 OK response).
>
> The problem happens when one of these sites that includes proxied  
> IPNI LSIDs is crawled by a search engine. The proxied links appear  
> to belong to tdwg.org, so whatever crawl delay is agreed between  
> TDWG and the crawler in question is used. The crawler has no  
> knowledge that behind the scenes the TDWG resolver is hitting  
> ipni.org. We (ipni.org) have agreed our own crawl limits with Google  
> and the other major search engines using directives in robots.txt  
> and directly agreed limits with Google (who don't use the robots.txt  
> directly).
>
> On a couple of occasions in the past we have had to deny access to  
> the TDWG LSID resolver as it has been responsible for far more  
> traffic than we can support (up to 10 times the crawl limits we have  
> agreed with search engine bots) - this due to the pages on the GBIF  
> portal and / or zipcodezoo being crawled by a search engine, which  
> in turn triggers a high volume of requests from TDWG to IPNI. The  
> crawler itself has no knowledge that it is in effect accessing data  
> held at ipni.org rather than tdwg.org as the HTTP response is HTTP  
> 200.
>
> One of Rod's emails recently mentioned that we need a resolver to  
> act like a tinyurl or bit.ly. I have pasted below the HTTP headers  
> for an HTTP request to the TDWG LSID resolver, and to tinyurl /  
> bit.ly. To the end user it looks as though tdwg.org is the true  
> location of the LSID resource, whereas with the tinyurl and bitly  
> both just redirect traffic.
>
> I'm just posting this for discussion really - if we are to mandate  
> use of a web based HTTP resolver/proxies, it should really issue 30*  
> redirects so that established crawl delays between producer and  
> consumer will be used. The alternative would be for the HTTP  
> resolver to read and process the directives in robots.txt, but this  
> would be difficult to implement as it is not in itself a crawler,  
> just a gateway.
>
> I'm sure that if proxied forms of LSIDs become more prevalent this  
> problem will become more widespread, so now - with the on-going  
> attempt to define what services a GUID resolver should provide -  
> might be a good time to plan how to fix this.
>
> cheers,
> Nicky
>
> [nn00kg at kvstage01 ~]$ curl -I http://lsid.tdwg.org/urn:lsid:ipni.org:names:783030-1
> HTTP/1.1 200 OK
> Via: 1.1 KISA01
> Connection: close
> Proxy-Connection: close
> Date: Mon, 27 Apr 2009 11:41:55 GMT
> Content-Type: application/xml
> Server: Apache/2.2.3 (CentOS)
>
> [nn00kg at kvstage01 ~]$ curl -I http://tinyurl.com/czkquy
> HTTP/1.1 301 Moved Permanently
> Via: 1.1 KISA01
> Connection: close
> Proxy-Connection: close
> Date: Mon, 27 Apr 2009 12:16:38 GMT
> Location: http://www.ipni.org/ipni/plantNameByVersion.do?id=783030-1&version=1.4&output_format=lsid-metadata&show_history=true
> Content-type: text/html
> Server: TinyURL/1.6
> X-Powered-By: PHP/5.2.9
>
> [nn00kg at kvstage01 ~]$ curl -I http://bit.ly/KO1Ko
> HTTP/1.1 301 Moved Permanently
> Via: 1.1 KISA01
> Connection: Keep-Alive
> Proxy-Connection: Keep-Alive
> Content-Length: 287
> Date: Mon, 27 Apr 2009 12:19:48 GMT
> Location: http://www.ipni.org/ipni/plantNameByVersion.do?id=783030-1&version=1.4&output_format=lsid-metadata&show_history=true
> Content-Type: text/html;charset=utf-8
> Server: nginx/0.7.42
> Allow: GET, HEAD, POST
>
>
>
> - Nicola Nicolson
> - Science Applications Development,
> - Royal Botanic Gardens, Kew,
> - Richmond, Surrey, TW9 3AB, UK
> - email: n.nicolson at rbgkew.org.uk
> - phone: 020-8332-5766
> _______________________________________________
> tdwg-tag mailing list
> tdwg-tag at lists.tdwg.org
> http://lists.tdwg.org/mailman/listinfo/tdwg-tag

---------------------------------------------------------
Roderic Page
Professor of Taxonomy
DEEB, FBLS
Graham Kerr Building
University of Glasgow
Glasgow G12 8QQ, UK

Email: r.page at bio.gla.ac.uk
Tel: +44 141 330 4778
Fax: +44 141 330 2792
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Home page: http://taxonomy.zoology.gla.ac.uk/rod/rod.html






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