com.sun.grizzly.util.SelectorFactory Maven / Gradle / Ivy
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package com.sun.grizzly.util;
import java.io.IOException;
import java.nio.channels.Selector;
import java.util.Queue;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.logging.Level;
import java.util.logging.Logger;
/**
* Factory used to dispatch/share {@link Selector}.
*
* @author Scott Oaks
* @author Jean-Francois Arcand
* @author gustav trede
*/
public final class SelectorFactory {
private static final int MISS_THRESHOLD = 10000;
public static final int DEFAULT_MAX_SELECTORS = 20;
/**
* The number of {@link Selector} to create.
*/
private static volatile int maxSelectors = DEFAULT_MAX_SELECTORS;
/**
* Cache of {@link Selector}
*/
private final static Queue selectors =
DataStructures.getCLQinstance(Selector.class);
/**
* The current number of Selectors in the pool.
*/
private final static AtomicInteger poolSize = new AtomicInteger();
/**
* Number of times poll execution didn't find the available selector in the pool.
*/
private final static AtomicInteger missesCounter = new AtomicInteger();
/**
* Set max selector pool size.
* @param size max pool size
*/
public static void setMaxSelectors(int size) {
if (size < 0) {
throw new IllegalArgumentException("size < 0");
}
missesCounter.set(0);
maxSelectors = size;
}
/**
* Returns max selector pool size
* @return max pool size
*/
public static int getMaxSelectors() {
return maxSelectors;
}
/**
* Please ensure to use try finally around get and return of selector so avoid leaks.
* Get a exclusive {@link Selector}
* @return {@link Selector}
*/
public static Selector getSelector() {
Selector selector = selectors.poll();
if (selector != null) {
poolSize.decrementAndGet();
} else {
try {
selector = Utils.openSelector();
} catch (IOException e) {
LoggerUtils.getLogger().log(Level.WARNING,
"SelectorFactory. Can not create a selector", e);
}
final int missesCount = missesCounter.incrementAndGet();
if (missesCount % MISS_THRESHOLD == 0) {
LoggerUtils.getLogger().log(Level.WARNING,
"SelectorFactory. Pool encounters a lot of misses {0}. "
+ "Increase default {1} pool size",
new Object[] {missesCount, maxSelectors});
}
}
return selector;
}
/**
* Please ensure to use try finally around get and return of selector so avoid leaks.
* Return the {@link Selector} to the cache
* @param s {@link Selector}
*/
public static void returnSelector(Selector s) {
if (poolSize.getAndIncrement() < maxSelectors) {
selectors.offer(s);
} else {
poolSize.decrementAndGet();
closeSelector(s);
}
}
/**
* Executes Selector.selectNow() and returns
* the {@link Selector} to the cache
*/
public static void selectNowAndReturnSelector(Selector s) {
try {
s.selectNow();
returnSelector(s);
} catch (IOException e) {
Logger logger = LoggerUtils.getLogger();
logger.log(Level.WARNING,
"Unexpected problem when releasing temporary Selector", e);
closeSelector(s);
}
}
private static void closeSelector(Selector s) {
try {
s.close();
} catch (IOException ignored) {
// We are not interested
}
}
}