Hi,
we have noticed a high CPU usage when a client send a SPARQL query
which returns a large result set and the client goes away when we
are streaming back the response.
I think I might have found the reason why the high CPU usage persist
even after the client went away.
We use ResultSetFormatter.outputAsXML(OutputStream outStream,
ResultSet qresults) which is then using IndentedWriter:
java.io.IOException.<init>(String)
simple.http.MonitoredOutputStream.ensureOpen()
simple.http.MonitoredOutputStream.write(byte[], int, int)
simple.http.ResponseStream.write(byte[], int, int)
java.io.PrintWriter.write(int)
org.openjena.atlas.io.IndentedWriter.write(char)
org.openjena.atlas.io.IndentedWriter.padInt()
org.openjena.atlas.io.IndentedWriter.lineStart()
org.openjena.atlas.io.IndentedWriter.printOneChar(char)
org.openjena.atlas.io.IndentedWriter.print(Object)
org.openjena.atlas.io.IndentedWriter.println(Object)
com.hp.hpl.jena.sparql.resultset.XMLOutputResultSet.printResource(Resource)
com.hp.hpl.jena.sparql.resultset.XMLOutputResultSet.printBindingValue(RDFNode)
com.hp.hpl.jena.sparql.resultset.XMLOutputResultSet.binding(String, RDFNode)
com.hp.hpl.jena.sparql.resultset.ResultSetApply.apply()
com.hp.hpl.jena.sparql.resultset.XMLOutput.format(OutputStream, ResultSet)
com.hp.hpl.jena.query.ResultSetFormatter.outputAsXML(OutputStream, ResultSet,
String)
com.hp.hpl.jena.query.ResultSetFormatter.outputAsXML(OutputStream, ResultSet)
If an IOException is generated, for example, because the client which
we were streaming the response to went away, the exception is swallowed
by the write method in IndentedWriter:
private void write(char ch)
{ try { out.write(ch) ; } catch (IOException ex) {} }
The problem does not depend on the particular web framework used.
I think Fuseki is affected by the same problem, but I have not time to replicate
it with Fuseki yet.
Am I missing something here?
Thank you,
Paolo
