Excessive re-request of same resource when slash (`/`) uris redirect to the same page

[jeswr]

Issue type:

• :snail: Performance issue

---

Description:

During link traversal the same resource seens to be re-requested many times in particular if I run the following script

// import { QueryEngine } from '@comunica/query-sparql';
import { getOwlClasses, getProperties, predictAllClasses } from './utils';
import { QueryEngine } from '@comunica/query-sparql-link-traversal';
import { DataFactory as DF } from 'n3';

async function main() {
  const engine = new QueryEngine();

  const WAYBACK_URL = 'http://wayback.archive-it.org/';

  function addWayback(action: any): any {
    const request = new Request(action.input, action.init);
    return {
      input: new Request(new URL(`/${request.url}`, WAYBACK_URL), request),
    };
  }

  const results = await engine.queryBindings(`
  PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
  PREFIX foaf: <http://xmlns.com/foaf/0.1/>

  SELECT ?type WHERE {
    foaf:Group (rdfs:subClassOf*/^rdfs:domain/rdfs:range)* ?type
  }`,
    {
      sources: [
        "http://xmlns.com/foaf/spec/20140114.rdf"
      ],
      lenient: true,
      httpProxyHandler: {
        async getProxy(request) {
          const res = await fetch(request.input, { method: 'HEAD' });
          console.log(res.status)
          if (res.status !== 200) {
            const newRequest = addWayback(request);
            const res = await fetch(newRequest.input, { method: 'HEAD' });
            console.log(res.status, res.url)
            if (res.status === 200) {
              console.log('new request', newRequest.input.toString())
              return newRequest;
            }
          }
          console.log('res', request.input.toString(), res.url)
          return request;
        }
      }
    }
  )
  const arr = await results.toArray();
  console.log(arr.map(r => r.get('type')))
}

main();

Then as a response I get the likes of

res http://xmlns.com/foaf/0.1/interest http://xmlns.com/foaf/0.1/
200
res http://xmlns.com/foaf/0.1/icqChatID http://xmlns.com/foaf/0.1/
200
res http://xmlns.com/foaf/0.1/topic_interest http://xmlns.com/foaf/0.1/
200
res http://xmlns.com/foaf/0.1/sha1 http://xmlns.com/foaf/0.1/
200
res http://xmlns.com/foaf/0.1/workInfoHomepage http://xmlns.com/foaf/0.1/
200
res http://xmlns.com/foaf/0.1/currentProject http://xmlns.com/foaf/0.1/
200
res http://xmlns.com/foaf/0.1/Document http://xmlns.com/foaf/0.1/
200
res http://xmlns.com/foaf/0.1/msnChatID http://xmlns.com/foaf/0.1/
200
res http://xmlns.com/foaf/0.1/logo http://xmlns.com/foaf/0.1/
200
res http://xmlns.com/foaf/0.1/theme http://xmlns.com/foaf/0.1/
200
res http://xmlns.com/foaf/0.1/img http://xmlns.com/foaf/0.1/
200
res http://xmlns.com/foaf/0.1/publications http://xmlns.com/foaf/0.1/
200
res http://xmlns.com/foaf/0.1/knows http://xmlns.com/foaf/0.1/
200
res http://xmlns.com/foaf/0.1/page http://xmlns.com/foaf/0.1/
200
res http://xmlns.com/foaf/0.1/topic http://xmlns.com/foaf/0.1/
200
res http://xmlns.com/foaf/0.1/pastProject http://xmlns.com/foaf/0.1/
200
res http://xmlns.com/foaf/0.1/Agent http://xmlns.com/foaf/0.1/
200
res http://xmlns.com/foaf/0.1/name http://xmlns.com/foaf/0.1/
200
res http://xmlns.com/foaf/0.1/fundedBy http://xmlns.com/foaf/0.1/
200
res http://xmlns.com/foaf/0.1/workplaceHomepage http://xmlns.com/foaf/0.1/
200
res http://xmlns.com/foaf/0.1/aimChatID http://xmlns.com/foaf/0.1/

It seems to me that it would be fairly safe in this instance to see that the response URL for http://xmlns.com/foaf/0.1/interest is http://xmlns.com/foaf/0.1/ and then use that cached resource for all future URLs starting with http://xmlns.com/foaf/0.1/ (or if you want to be safe to a headers request only on future URLs to confirm they redirect to the cached page) - I think it would also be safe to have a greater parellisation on the headers requests compared to get requests.

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Environment:

[github-actions[bot]]

Thanks for reporting!

[rubensworks]

Let's merge this issue into #61, as it seems to describe the same problem AFAICS.