/*
* @(#)$Id: LeastPendingRequestsFirstScheduler.java 3619 2008-03-26 07:23:03Z yui $
*
* Copyright 2006-2008 Makoto YUI
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* Contributors:
* Makoto YUI - initial implementation
*/
package xbird.server.sched;
import java.util.concurrent.locks.*;
import xbird.server.Request;
import xbird.server.backend.BackendProcessor;
import xbird.server.repository.IDocumentRepository;
/**
*
* <DIV lang="en"></DIV>
* <DIV lang="ja"></DIV>
*
* @author Makoto YUI (yuin405+xbird@gmail.com)
*/
public class LeastPendingRequestsFirstScheduler extends AbstractScheduler {
public static final String LPRF = "lprf";
private final Lock _readLock;
private final Lock _writeLock;
private final int _numProcs;
private final int[] _pendingCounts;
public LeastPendingRequestsFirstScheduler(BackendProcessor[] procs, IDocumentRepository repository) {
super(procs, repository);
this._numProcs = procs.length;
this._pendingCounts = new int[procs.length];
final ReadWriteLock rwl = new ReentrantReadWriteLock();
this._readLock = rwl.readLock();
this._writeLock = rwl.writeLock();
}
@Override
public BackendProcessor dispatchRequest(Request request) {
int leastIndex = 0, minCnt = 0;
_readLock.lock();
for(int i = 0; i < _numProcs; i++) {
final int cnt = _pendingCounts[i];
if(cnt < minCnt) {
leastIndex = i;
minCnt = cnt;
}
}
final BackendProcessor qp = _procs[leastIndex];
_readLock.unlock();
_writeLock.lock();
++_pendingCounts[leastIndex];
_writeLock.unlock();
return qp;
}
@Override
public void notifyCompletion(Request request) {
final int qpid = request.getAttachedQueryProcessorId();
_writeLock.lock();
--_pendingCounts[qpid];
_writeLock.unlock();
}
}