/*
* $Header$
* $Revision: 982 $
* $Date: 2006-12-08 18:42:51 +1000 (Fri, 08 Dec 2006) $
*
* ====================================================================
*
* The Apache Software License, Version 1.1
*
* Copyright (c) 2003-2009 The JRDF Project. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. The end-user documentation included with the redistribution, if
* any, must include the following acknowlegement:
* "This product includes software developed by the
* the JRDF Project (http://jrdf.sf.net/)."
* Alternately, this acknowlegement may appear in the software itself,
* if and wherever such third-party acknowlegements normally appear.
*
* 4. The names "The JRDF Project" and "JRDF" must not be used to endorse
* or promote products derived from this software without prior written
* permission. For written permission, please contact
* newmana@users.sourceforge.net.
*
* 5. Products derived from this software may not be called "JRDF"
* nor may "JRDF" appear in their names without prior written
* permission of the JRDF Project.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the JRDF Project. For more
* information on JRDF, please see <http://jrdf.sourceforge.net/>.
*
*/
package org.jrdf.query.server.distributed;
import org.jrdf.query.answer.Answer;
import org.jrdf.query.answer.StreamingAnswerSparqlParser;
import org.jrdf.query.answer.StreamingAnswerSparqlParserImpl;
import org.jrdf.query.answer.StreamingAnswerSparqlParserSelectAnswer;
import org.jrdf.query.client.CallableQueryClient;
import org.jrdf.query.client.CallableQueryClientImpl;
import org.jrdf.query.client.QueryClient;
import org.jrdf.query.client.SparqlAnswerHandler;
import static org.jrdf.util.param.ParameterUtil.checkNotNull;
import java.net.URI;
import java.util.Collection;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Future;
import java.util.concurrent.ScheduledThreadPoolExecutor;
/**
* @author Yuan-Fang Li
* @version :$
*/
public class DistributedQueryClientImpl implements QueryClient {
private ExecutorService executor;
private Collection<CallableQueryClient> queryClients;
private Set<Future<Answer>> answers;
private StreamingAnswerSparqlParser multiAnswerParser;
public DistributedQueryClientImpl(final Collection<URI> servers, final SparqlAnswerHandler answerHandler) {
this.queryClients = new LinkedList<CallableQueryClient>();
for (final URI server : servers) {
final CallableQueryClient client = new CallableQueryClientImpl(server, answerHandler);
this.queryClients.add(client);
}
this.executor = new ScheduledThreadPoolExecutor(servers.size());
this.multiAnswerParser = new StreamingAnswerSparqlParserImpl();
}
public void setQuery(final String queryString, final Map<String, String> queryExtensions) {
for (final QueryClient queryClient : queryClients) {
queryClient.setQuery(queryString, queryExtensions);
}
}
public Answer executeQuery() {
checkNotNull(queryClients);
this.answers = new HashSet<Future<Answer>>();
executeQuries();
aggregateResults();
// TODO AN This should use the AnswerHandler.
return new StreamingAnswerSparqlParserSelectAnswer(multiAnswerParser);
}
public Answer executeQuery(final String queryString, final Map<String, String> ext) {
setQuery(queryString, ext);
return executeQuery();
}
public void cancelExecution() {
for (final Future<Answer> future : answers) {
cancelExecution(future);
}
}
private void aggregateResults() {
final long start = System.currentTimeMillis();
for (final Future<Answer> future : answers) {
try {
final Answer answer = future.get();
multiAnswerParser.addAnswer(answer);
} catch (Exception e) {
cancelExecution(future);
}
}
System.out.println("Distributed querying time: " + (System.currentTimeMillis() - start));
}
private void executeQuries() {
for (final CallableQueryClient queryClient : queryClients) {
final Future<Answer> future = executor.submit(queryClient);
answers.add(future);
}
}
private void cancelExecution(final Future<Answer> future) {
future.cancel(true);
}
}