Hello,

When we issue queries using the MWAPI [1] programatically, we sometimes get a 500 error. I would guess that happens in more than 30% of the cases. The following SPARQL query causes the error:

    SELECT DISTINCT *
    WHERE {
        SERVICE wikibase:mwapi {
            bd:serviceParam wikibase:api "EntitySearch" .
            bd:serviceParam wikibase:endpoint "www.wikidata.org" .
            bd:serviceParam wikibase:limit "once" .
            bd:serviceParam mwapi:search "integre" .
            bd:serviceParam mwapi:language "en" .
            ?subj wikibase:apiOutputItem mwapi:item .
        }
    }
    LIMIT 2000

When calling the SPARQL endpoint from e.g. Python (sparqlwrapper) or Java (rdf4j), I sometimes get the following stack trace:

    SPARQL-QUERY: queryStr=
    SELECT DISTINCT *
    WHERE {
            SERVICE wikibase:mwapi {
                bd:serviceParam wikibase:api "EntitySearch" .
            bd:serviceParam wikibase:endpoint "www.wikidata.org" .
            bd:serviceParam wikibase:limit "once" .
            bd:serviceParam mwapi:search "integre" .
            bd:serviceParam mwapi:language "en" .
            ?subj wikibase:apiOutputItem mwapi:item .
        }
    }
    LIMIT 2000
    java.util.concurrent.ExecutionException: java.util.concurrent.ExecutionException: org.openrdf.query.QueryEvaluationException: java.lang.RuntimeException: java.util.concurrent.ExecutionException: java.lang.RuntimeException: java.util.concurrent.ExecutionException: java.lang.Exception: task=ChunkTask{query=66f912d3-e0e8-4bb7-93fe-1ebb044e5ade,bopId=1,partitionId=-1,sinkId=2,altSinkId=null}, cause=java.util.concurrent.ExecutionException: java.util.concurrent.ExecutionException: java.lang.RuntimeException: java.lang.RuntimeException: MWAPI request failed
        at java.util.concurrent.FutureTask.report(FutureTask.java:122)
        at java.util.concurrent.FutureTask.get(FutureTask.java:206)
        at com.bigdata.rdf.sail.webapp.BigdataServlet.submitApiTask(BigdataServlet.java:292)
        at com.bigdata.rdf.sail.webapp.QueryServlet.doSparqlQuery(QueryServlet.java:678)
        at com.bigdata.rdf.sail.webapp.QueryServlet.doGet(QueryServlet.java:290)
        at com.bigdata.rdf.sail.webapp.RESTServlet.doGet(RESTServlet.java:240)
        at com.bigdata.rdf.sail.webapp.MultiTenancyServlet.doGet(MultiTenancyServlet.java:273)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:687)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
        at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:865)
        at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1655)
        at org.wikidata.query.rdf.blazegraph.throttling.ThrottlingFilter.doFilter(ThrottlingFilter.java:320)
        at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1642)
        at org.wikidata.query.rdf.blazegraph.throttling.SystemOverloadFilter.doFilter(SystemOverloadFilter.java:82)
        at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1642)
        at ch.qos.logback.classic.helpers.MDCInsertingServletFilter.doFilter(MDCInsertingServletFilter.java:49)
        at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1642)
        at org.wikidata.query.rdf.blazegraph.filters.QueryEventSenderFilter.doFilter(QueryEventSenderFilter.java:93)
        at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1642)
        at org.wikidata.query.rdf.blazegraph.filters.ClientIPFilter.doFilter(ClientIPFilter.java:43)
        at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1642)
        at org.wikidata.query.rdf.blazegraph.filters.RealAgentFilter.doFilter(RealAgentFilter.java:33)
        at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1634)
        at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:533)
        at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:146)
        at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:548)
        at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:132)
        at org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:257)
        at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:1595)
        at org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:255)
        at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1340)
        at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:203)
        at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:473)
        at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:1564)
        at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:201)
        at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1242)
        at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:144)
        at org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:220)
        at org.eclipse.jetty.server.handler.HandlerCollection.handle(HandlerCollection.java:126)
        at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:132)
        at org.eclipse.jetty.server.Server.handle(Server.java:503)
        at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:364)
        at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:260)
        at org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:305)
        at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:103)
        at org.eclipse.jetty.io.ChannelEndPoint$2.run(ChannelEndPoint.java:118)
        at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.runTask(EatWhatYouKill.java:333)
        at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.doProduce(EatWhatYouKill.java:310)
        at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.tryProduce(EatWhatYouKill.java:168)
        at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.run(EatWhatYouKill.java:126)
        at org.eclipse.jetty.util.thread.ReservedThreadExecutor$ReservedThread.run(ReservedThreadExecutor.java:366)
        at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:765)
        at org.eclipse.jetty.util.thread.QueuedThreadPool$2.run(QueuedThreadPool.java:683)
        at java.lang.Thread.run(Thread.java:748)
    Caused by: java.util.concurrent.ExecutionException: org.openrdf.query.QueryEvaluationException: java.lang.RuntimeException: java.util.concurrent.ExecutionException: java.lang.RuntimeException: java.util.concurrent.ExecutionException: java.lang.Exception: task=ChunkTask{query=66f912d3-e0e8-4bb7-93fe-1ebb044e5ade,bopId=1,partitionId=-1,sinkId=2,altSinkId=null}, cause=java.util.concurrent.ExecutionException: java.util.concurrent.ExecutionException: java.lang.RuntimeException: java.lang.RuntimeException: MWAPI request failed
        at java.util.concurrent.FutureTask.report(FutureTask.java:122)
        at java.util.concurrent.FutureTask.get(FutureTask.java:192)
        at com.bigdata.rdf.sail.webapp.QueryServlet$SparqlQueryTask.call(QueryServlet.java:889)
        at com.bigdata.rdf.sail.webapp.QueryServlet$SparqlQueryTask.call(QueryServlet.java:695)
        at com.bigdata.rdf.task.ApiTaskForIndexManager.call(ApiTaskForIndexManager.java:68)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        ... 1 more
    Caused by: org.openrdf.query.QueryEvaluationException: java.lang.RuntimeException: java.util.concurrent.ExecutionException: java.lang.RuntimeException: java.util.concurrent.ExecutionException: java.lang.Exception: task=ChunkTask{query=66f912d3-e0e8-4bb7-93fe-1ebb044e5ade,bopId=1,partitionId=-1,sinkId=2,altSinkId=null}, cause=java.util.concurrent.ExecutionException: java.util.concurrent.ExecutionException: java.lang.RuntimeException: java.lang.RuntimeException: MWAPI request failed
        at com.bigdata.rdf.sail.Bigdata2Sesame2BindingSetIterator.hasNext(Bigdata2Sesame2BindingSetIterator.java:188)
        at info.aduna.iteration.IterationWrapper.hasNext(IterationWrapper.java:68)
        at org.openrdf.query.QueryResults.report(QueryResults.java:155)
        at org.openrdf.repository.sail.SailTupleQuery.evaluate(SailTupleQuery.java:76)
        at com.bigdata.rdf.sail.webapp.BigdataRDFContext$TupleQueryTask.doQuery(BigdataRDFContext.java:1722)
        at com.bigdata.rdf.sail.webapp.BigdataRDFContext$AbstractQueryTask.innerCall(BigdataRDFContext.java:1579)
        at com.bigdata.rdf.sail.webapp.BigdataRDFContext$AbstractQueryTask.call(BigdataRDFContext.java:1544)
        at com.bigdata.rdf.sail.webapp.BigdataRDFContext$AbstractQueryTask.call(BigdataRDFContext.java:757)
        ... 4 more
    Caused by: java.lang.RuntimeException: java.util.concurrent.ExecutionException: java.lang.RuntimeException: java.util.concurrent.ExecutionException: java.lang.Exception: task=ChunkTask{query=66f912d3-e0e8-4bb7-93fe-1ebb044e5ade,bopId=1,partitionId=-1,sinkId=2,altSinkId=null}, cause=java.util.concurrent.ExecutionException: java.util.concurrent.ExecutionException: java.lang.RuntimeException: java.lang.RuntimeException: MWAPI request failed
        at com.bigdata.relation.accesspath.BlockingBuffer$BlockingIterator.checkFuture(BlockingBuffer.java:1523)
        at com.bigdata.relation.accesspath.BlockingBuffer$BlockingIterator._hasNext(BlockingBuffer.java:1710)
        at com.bigdata.relation.accesspath.BlockingBuffer$BlockingIterator.hasNext(BlockingBuffer.java:1563)
        at com.bigdata.striterator.AbstractChunkedResolverator._hasNext(AbstractChunkedResolverator.java:365)
        at com.bigdata.striterator.AbstractChunkedResolverator.hasNext(AbstractChunkedResolverator.java:341)
        at com.bigdata.rdf.sail.Bigdata2Sesame2BindingSetIterator.hasNext(Bigdata2Sesame2BindingSetIterator.java:134)
        ... 11 more
    Caused by: java.util.concurrent.ExecutionException: java.lang.RuntimeException: java.util.concurrent.ExecutionException: java.lang.Exception: task=ChunkTask{query=66f912d3-e0e8-4bb7-93fe-1ebb044e5ade,bopId=1,partitionId=-1,sinkId=2,altSinkId=null}, cause=java.util.concurrent.ExecutionException: java.util.concurrent.ExecutionException: java.lang.RuntimeException: java.lang.RuntimeException: MWAPI request failed
        at java.util.concurrent.FutureTask.report(FutureTask.java:122)
        at java.util.concurrent.FutureTask.get(FutureTask.java:192)
        at com.bigdata.relation.accesspath.BlockingBuffer$BlockingIterator.checkFuture(BlockingBuffer.java:1454)
        ... 16 more
    Caused by: java.lang.RuntimeException: java.util.concurrent.ExecutionException: java.lang.Exception: task=ChunkTask{query=66f912d3-e0e8-4bb7-93fe-1ebb044e5ade,bopId=1,partitionId=-1,sinkId=2,altSinkId=null}, cause=java.util.concurrent.ExecutionException: java.util.concurrent.ExecutionException: java.lang.RuntimeException: java.lang.RuntimeException: MWAPI request failed
        at com.bigdata.rdf.sail.RunningQueryCloseableIterator.checkFuture(RunningQueryCloseableIterator.java:59)
        at com.bigdata.rdf.sail.RunningQueryCloseableIterator.close(RunningQueryCloseableIterator.java:73)
        at com.bigdata.rdf.sail.RunningQueryCloseableIterator.hasNext(RunningQueryCloseableIterator.java:82)
        at com.bigdata.striterator.ChunkedWrappedIterator.hasNext(ChunkedWrappedIterator.java:197)
        at com.bigdata.striterator.AbstractChunkedResolverator$ChunkConsumerTask.call(AbstractChunkedResolverator.java:222)
        at com.bigdata.striterator.AbstractChunkedResolverator$ChunkConsumerTask.call(AbstractChunkedResolverator.java:197)
        ... 4 more
    Caused by: java.util.concurrent.ExecutionException: java.lang.Exception: task=ChunkTask{query=66f912d3-e0e8-4bb7-93fe-1ebb044e5ade,bopId=1,partitionId=-1,sinkId=2,altSinkId=null}, cause=java.util.concurrent.ExecutionException: java.util.concurrent.ExecutionException: java.lang.RuntimeException: java.lang.RuntimeException: MWAPI request failed
        at com.bigdata.util.concurrent.Haltable.get(Haltable.java:273)
        at com.bigdata.bop.engine.AbstractRunningQuery.get(AbstractRunningQuery.java:1516)
        at com.bigdata.bop.engine.AbstractRunningQuery.get(AbstractRunningQuery.java:104)
        at com.bigdata.rdf.sail.RunningQueryCloseableIterator.checkFuture(RunningQueryCloseableIterator.java:46)
        ... 9 more
    Caused by: java.lang.Exception: task=ChunkTask{query=66f912d3-e0e8-4bb7-93fe-1ebb044e5ade,bopId=1,partitionId=-1,sinkId=2,altSinkId=null}, cause=java.util.concurrent.ExecutionException: java.util.concurrent.ExecutionException: java.lang.RuntimeException: java.lang.RuntimeException: MWAPI request failed
        at com.bigdata.bop.engine.ChunkedRunningQuery$ChunkTask.call(ChunkedRunningQuery.java:1367)
        at com.bigdata.bop.engine.ChunkedRunningQuery$ChunkTaskWrapper.run(ChunkedRunningQuery.java:926)
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at com.bigdata.concurrent.FutureTaskMon.run(FutureTaskMon.java:63)
        at com.bigdata.bop.engine.ChunkedRunningQuery$ChunkFutureTask.run(ChunkedRunningQuery.java:821)
        ... 3 more
    Caused by: java.util.concurrent.ExecutionException: java.util.concurrent.ExecutionException: java.lang.RuntimeException: java.lang.RuntimeException: MWAPI request failed
        at java.util.concurrent.FutureTask.report(FutureTask.java:122)
        at java.util.concurrent.FutureTask.get(FutureTask.java:192)
        at com.bigdata.bop.engine.ChunkedRunningQuery$ChunkTask.call(ChunkedRunningQuery.java:1347)
        ... 8 more
    Caused by: java.util.concurrent.ExecutionException: java.lang.RuntimeException: java.lang.RuntimeException: MWAPI request failed
        at java.util.concurrent.FutureTask.report(FutureTask.java:122)
        at java.util.concurrent.FutureTask.get(FutureTask.java:206)
        at com.bigdata.bop.controller.ServiceCallJoin$ChunkTask.doServiceCallWithConstant(ServiceCallJoin.java:351)
        at com.bigdata.bop.controller.ServiceCallJoin$ChunkTask.call(ServiceCallJoin.java:303)
        at com.bigdata.bop.controller.ServiceCallJoin$ChunkTask.call(ServiceCallJoin.java:215)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at com.bigdata.bop.engine.ChunkedRunningQuery$ChunkTask.call(ChunkedRunningQuery.java:1346)
        ... 8 more
    Caused by: java.lang.RuntimeException: java.lang.RuntimeException: MWAPI request failed
        at com.bigdata.bop.controller.ServiceCallJoin$ChunkTask$ServiceCallTask.doServiceCall(ServiceCallJoin.java:757)
        at com.bigdata.bop.controller.ServiceCallJoin$ChunkTask$ServiceCallTask.call(ServiceCallJoin.java:616)
        at com.bigdata.bop.controller.ServiceCallJoin$ChunkTask$ServiceCallTask.call(ServiceCallJoin.java:552)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        ... 3 more
    Caused by: java.lang.RuntimeException: MWAPI request failed
        at org.wikidata.query.rdf.blazegraph.mwapi.MWApiServiceCall$ContinueIterator.doSearchRequest(MWApiServiceCall.java:488)
        at org.wikidata.query.rdf.blazegraph.mwapi.MWApiServiceCall$ContinueIterator.<init>(MWApiServiceCall.java:453)
        at org.wikidata.query.rdf.blazegraph.mwapi.MWApiServiceCall$MultiSearchIterator.doNextSearch(MWApiServiceCall.java:391)
        at org.wikidata.query.rdf.blazegraph.mwapi.MWApiServiceCall$MultiSearchIterator.<init>(MWApiServiceCall.java:352)
        at org.wikidata.query.rdf.blazegraph.mwapi.MWApiServiceCall.call(MWApiServiceCall.java:160)
        at org.wikidata.query.rdf.blazegraph.mwapi.MWApiServiceCall.call(MWApiServiceCall.java:66)
        at com.bigdata.bop.controller.ServiceCallJoin$ChunkTask$ServiceCallTask.doBigdataServiceCall(ServiceCallJoin.java:770)
        at com.bigdata.bop.controller.ServiceCallJoin$ChunkTask$ServiceCallTask.doServiceCall(ServiceCallJoin.java:707)
        ... 6 more
    Caused by: java.util.concurrent.TimeoutException
        at org.eclipse.jetty.client.util.InputStreamResponseListener.get(InputStreamResponseListener.java:216)
        at org.wikidata.query.rdf.blazegraph.mwapi.MWApiServiceCall$ContinueIterator.doSearchRequest(MWApiServiceCall.java:477)
        ... 13 more

I use the following Python script to call the service, I assume http maybe also works:

    from SPARQLWrapper import SPARQLWrapper, JSON

    queryString = """
    SELECT DISTINCT *
    WHERE {
        SERVICE wikibase:mwapi {
            bd:serviceParam wikibase:api "EntitySearch" .
            bd:serviceParam wikibase:endpoint "www.wikidata.org" .
            bd:serviceParam wikibase:limit "once" .
            bd:serviceParam mwapi:search "integre" .
            bd:serviceParam mwapi:language "en" .
            ?subj wikibase:apiOutputItem mwapi:item .
        }
    }
    LIMIT 2000
    """


    sparql = SPARQLWrapper("https://query.wikidata.org/sparql", returnFormat=JSON)
    sparql.setQuery(queryString)
    results = sparql.query().convert()
    print(results)

Can we do something about this? Why does it throw a "java.util.concurrent.TimeoutException" on your side? Thank you very much for this service, it is very useful for us.

Best,

[1]: https://www.mediawiki.org/wiki/Wikidata_Query_Service/User_Manual/MWAPI
    
 Jan-Christoph Klie, M. Sc.
 Doctoral Researcher
 Ubiquitous Knowledge Processing (UKP) Lab
 FB 20 / Department of Computer Science
 Technische Universität Darmstadt
 Hochschulstr. 10, 64289 Darmstadt, Germany
 phone +49 (0)6151 16-25297 room S2|02|B111
 https://www.ukp.tu-darmstadt.de