HI Gerber,
I asked this question some time ago on the DBpedia Mailing List. I
would still be very grateful if anybody could tell me the setting I
need to change in order to avoid the 502 Proxy Error. I want to fix
that for the DBpedia Live Endpoint.
The fix i made was not a Virtuoso setting, but a proxy setting.
The http://live.dbpedia.org/sparql endpoint, i think it is using a
Apache proxy as a front end.
Without having access to the error logs, it is hard for me to
speculate the exact problem, but there are two possibilities:
1. DBPedia can generate large headers due to alternate LINK in http
HEAD, so the proxy should
be configured with larger settings for header packets.
2. Apache proxy timeout is too small for using long running queries as
yours, so it times out
before getting response from the virtuoso server. This is the most
likely scenario in your case.
In both cases some simple tweaking of the apache settings, should
resolve this.
Unfortunately at this time apache.org times out on me, so i cannot
point you to the individual pages
with the exact names of the settings.
Patrick
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OpenLink Software
