Last modified: 2014-05-15 13:37:59 UTC
For some entities using Wikidata's Special:EntityData linked data URIs return HTTP 503. $ curl -I https://www.wikidata.org/wiki/Special:EntityData/Q30.json HTTP/1.1 503 Service Unavailable $ curl -I https://www.wikidata.org/wiki/Special:EntityData/Q30.nt HTTP/1.1 503 Service Unavailable $ curl -I https://www.wikidata.org/wiki/Special:EntityData/Q30.rdf HTTP/1.1 503 Service Unavailable Access via api.php works fine: $ curl -I "https://www.wikidata.org/w/api.php?action=wbgetentities&ids=q30&format=json" HTTP/1.1 200 OK Other examples: * Q30 * Q148 * Q145
Hypothesis: large entities trigger an Out Out Memory error, because SpecialEntityData uses output buffering on the JSON, effectively doubling the memory footprint of the serialized entity.
So, according to Chris & Chad, since this error doesn't show in fatal.log, it's not an OutOfMemory error. And it's not a timeout either. We'll need assistance from someone with shell access to identify the problem.
the error is: Request: GET http://www.wikidata.org/wiki/Special:EntityData/Q30.json, from 10.64.0.102 via cp1065 cp1065 ([10.64.0.102]:3128), Varnish XID 2665166859<br/>Forwarded for: 87.138.110.76, 91.198.174.103, 208.80.154.77, 10.64.0.102<br/>Error: 503, Service Unavailable at Thu, 06 Feb 2014 17:30:26 GMT seems to come from varnish. Maybe we are hitting some memory or other limit?
According to Katie, it's a problem with Varnish: [18:31] <aude> DanielK_WMDE: it says "Varnish XID 2665166859" [18:32] <aude> tells me it probably is varnish [18:33] <aude> it's a text varnish cache [18:33] <aude> cp1065.eqiad.wmnet So I suppose we'll have to ask Mark about it.
This indeed is a varnish problem, fetching the data directly from one of the apache's works fine (and fast).
Varnish 503s with this error message: 170 FetchError c straight insufficient bytes which I think is a problem with compression that we've seen before. See if this varies whether or not you send an Accept-Encoding header of gzip/deflate or not?
Change 131746 had a related patch set uploaded by Hoo man: Don't set Content-Length in EntityDataRequestHandler https://gerrit.wikimedia.org/r/131746
Change 131746 merged by jenkins-bot: Don't set Content-Length in EntityDataRequestHandler https://gerrit.wikimedia.org/r/131746
