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https://issues.apache.org/jira/browse/JENA-289?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13478239#comment-13478239
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Simon Helsen commented on JENA-289:
-----------------------------------
I have a question about the abort and the problem reported here. Right now, we
are looking into a workaround that if a bad query occurs and abort is
requested, we just keep requesting the abort (like every so many seconds) until
the abort works. The reason is that from the explanation above, it seems that
the abort only doesn't catch until the first result is returned (i.e. the
iterator starts). Now, we have a instance of an expensive query which we try to
abort after 30 seconds. That doesn't seem to work, so I keep calling
QueryExecution.abort() every 5 seconds. Yet, the query keeps going and after 16
minutes, we hit the OME because the journal is exploding.
I can't seem to find in the code why ARQ would not keep trying to abort if it
is requested more than once. We will try to examine where the query is hanging
during these 16 minutes, but my question was mostly to try to understand if our
strategy to keep requesting abort() on the QueryExecution (in a separate thread
of course), would eventually have to work
> Respect query timeouts in TDB implementation
> --------------------------------------------
>
> Key: JENA-289
> URL: https://issues.apache.org/jira/browse/JENA-289
> Project: Apache Jena
> Issue Type: Improvement
> Components: TDB
> Affects Versions: TDB 0.9.1
> Reporter: Mark Buquor
> Attachments: TestTimeout.java, TestTimeout.java
>
>
> In general use, we sometimes see queries throw QueryCancelledException
> several seconds/minutes after the expected timeout. This is acceptable to a
> degree, but it appears that there are cases where a rogue query could execute
> unmitigated. The attached testcase is an example of a query that will execute
> and consume CPU/heap until an OutOfMemoryError is thrown.
> Example: The following query with 10s timeouts executed for ~7 minutes before
> throwing an OOME.
> Aug 3, 2012 10:18:19 AM Executing query [limit=1,000 timeout1=10s
> timeout2=10s]: SELECT * WHERE { ?a ?b ?c . ?c ?d ?e }
> java.lang.OutOfMemoryError: GC overhead limit exceeded
> at java.util.HashSet.<init>(HashSet.java:86)
> at org.openjena.atlas.iterator.FilterUnique.<init>(FilterUnique.java:26)
> at org.openjena.atlas.iterator.Iter.distinct(Iter.java:438)
> at
> com.hp.hpl.jena.tdb.solver.StageMatchTuple.makeNextStage(StageMatchTuple.java:116)
> at
> com.hp.hpl.jena.tdb.solver.StageMatchTuple.makeNextStage(StageMatchTuple.java:44)
> at
> org.openjena.atlas.iterator.RepeatApplyIterator.hasNext(RepeatApplyIterator.java:49)
> at org.openjena.atlas.iterator.Iter$4.hasNext(Iter.java:295)
> at
> com.hp.hpl.jena.sparql.engine.iterator.QueryIterPlainWrapper.hasNextBinding(QueryIterPlainWrapper.java:54)
> at
> com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:108)
> at
> com.hp.hpl.jena.sparql.engine.iterator.QueryIterSlice.hasNextBinding(QueryIterSlice.java:76)
> at
> com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:108)
> at
> com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorWrapper.hasNextBinding(QueryIteratorWrapper.java:40)
> at
> com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:108)
> at
> com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorWrapper.hasNextBinding(QueryIteratorWrapper.java:40)
> at
> com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:108)
> at
> com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorWrapper.hasNextBinding(QueryIteratorWrapper.java:40)
> at
> com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:108)
> at
> com.hp.hpl.jena.sparql.engine.ResultSetStream.hasNext(ResultSetStream.java:72)
> at
> com.hp.hpl.jena.sparql.resultset.ResultSetApply.apply(ResultSetApply.java:41)
> at com.hp.hpl.jena.sparql.resultset.XMLOutput.format(XMLOutput.java:52)
> at
> com.hp.hpl.jena.query.ResultSetFormatter.outputAsXML(ResultSetFormatter.java:482)
> at
> com.hp.hpl.jena.query.ResultSetFormatter.outputAsXML(ResultSetFormatter.java:460)
> at TestTimout.main(TestTimout.java:84)
> Aug 3, 2012 10:25:41 AM Finished
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