/*
***** BEGIN LICENSE BLOCK *****
* Version: CPL 1.0/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Common Public
* License Version 1.0 (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.eclipse.org/legal/cpl-v10.html
*
* Software distributed under the License is distributed on an "AS
* IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
* implied. See the License for the specific language governing
* rights and limitations under the License.
*
* Copyright (C) 2010 Charles O Nutter <headius@headius.com>
*
* Alternatively, the contents of this file may be used under the terms of
* either of the GNU General Public License Version 2 or later (the "GPL"),
* or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
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package org.jruby.util.io;
import java.io.IOException;
import java.nio.channels.Selector;
import java.util.List;
import java.nio.channels.spi.SelectorProvider;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.Map;
/**
* This is a simple implementation of a hard-referenced java.nio.channels.Selector
* pool. It is intended to allow us to reuse a small pool of selectors rather
* than creating them new for each use (which causes problem for Windows and
* its socket-per-selector impl) or saving them per-thread (which causes
* problems when there are many not-quite-dead threads in flight.
*
* The selectors are kept open in the pool and you should call {@link #cleanup()}
* for releasing selectors.
*
* @author headius
*/
public class SelectorPool {
private final Map<SelectorProvider, List<Selector>> pool = new HashMap<SelectorProvider, List<Selector>>();
/**
* Get a selector from the pool (or create a new one). Selectors come from
* the default selector provider on the current JVM.
*
* @return a java.nio.channels.Selector
* @throws IOException if there's a problem opening a new selector
*/
public synchronized Selector get() throws IOException{
return retrieveFromPool(SelectorProvider.provider());
}
/**
* Get a selector from the pool (or create a new one). Selectors come from
* the given provider.
*
* @return a java.nio.channels.Selector
* @throws IOException if there's a problem opening a new selector
*/
public synchronized Selector get(SelectorProvider provider) throws IOException{
return retrieveFromPool(provider);
}
/**
* Put a selector back into the pool.
*
* @param selector the selector to put back
*/
public synchronized void put(Selector selector) {
returnToPool(selector);
}
/**
* Clean up a pool.
*
* All selectors in a pool are closed and the pool gets empty.
*
*/
public synchronized void cleanup() {
for (Map.Entry<SelectorProvider, List<Selector>> entry : pool.entrySet()) {
List<Selector> providerPool = entry.getValue();
while (!providerPool.isEmpty()) {
Selector selector = providerPool.remove(providerPool.size() - 1);
try {
selector.close();
} catch (IOException ioe) {
// ignore IOException at termination.
}
}
}
pool.clear();
}
private Selector retrieveFromPool(SelectorProvider provider) throws IOException {
List<Selector> providerPool = pool.get(provider);
if (providerPool != null && !providerPool.isEmpty()) {
return providerPool.remove(providerPool.size() - 1);
}
return SelectorFactory.openWithRetryFrom(null, provider);
}
private void returnToPool(Selector selector) {
SelectorProvider provider = selector.provider();
List<Selector> providerPool = pool.get(provider);
if (providerPool == null) {
providerPool = new LinkedList<Selector>();
pool.put(provider, providerPool);
}
providerPool.add(selector);
}
}