com.sun.grizzly.util.SelectorFactory Maven / Gradle / Ivy
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package com.sun.grizzly.util;
import com.sun.grizzly.Controller;
import java.io.IOException;
import java.nio.channels.Selector;
import java.util.EmptyStackException;
import java.util.Stack;
import java.util.logging.Level;
import java.util.logging.Logger;
/**
* Factory used to dispatch/share {@link Selector}.
*
* @author Scott Oaks
* @author Jean-Francois Arcand
*/
public class SelectorFactory{
public static final int DEFAULT_MAX_SELECTORS = 20;
/**
* The timeout before we exit.
*/
public static long timeout = 5000;
/**
* The number of {@link Selector} to create.
*/
private static int maxSelectors = DEFAULT_MAX_SELECTORS;
/**
* Cache of {@link Selector}
*/
private final static Stack selectors = new Stack();
/**
* have we created the Selector instances.
*/
private static boolean initialized = false;
/**
* Set max selector pool size.
* @param size max pool size
*/
public final static void setMaxSelectors(int size) throws IOException {
synchronized(selectors) {
if (size > maxSelectors || !initialized) {
// if not initialized yet - grow cache by size
if (!initialized) maxSelectors = 0;
grow(size);
} else if (size < maxSelectors) {
reduce(size);
}
maxSelectors = size;
initialized = true;
}
}
/**
* Returns max selector pool size
* @return max pool size
*/
public final static int getMaxSelectors() {
return maxSelectors;
}
/**
* Get a exclusive {@link Selector}
* @return {@link Selector}
*/
public final static Selector getSelector() {
synchronized(selectors) {
if (!initialized) {
try {
setMaxSelectors(maxSelectors);
} catch (IOException e) {
Logger logger = Controller.logger();
if (logger.isLoggable(Level.WARNING)) {
logger.log(Level.WARNING, "SelectorFactory lazy initialization", e);
}
}
}
Selector s = null;
try {
if ( selectors.size() != 0 )
s = selectors.pop();
} catch (EmptyStackException ex){}
int attempts = 0;
try{
while (s == null && attempts < 2) {
selectors.wait(timeout);
try {
if ( selectors.size() != 0 )
s = selectors.pop();
} catch (EmptyStackException ex){
break;
}
attempts++;
}
} catch (InterruptedException ex){}
return s;
}
}
/**
* Return the {@link Selector} to the cache
* @param s {@link Selector}
*/
public final static void returnSelector(Selector s) {
synchronized(selectors) {
selectors.push(s);
if (selectors.size() == 1)
selectors.notify();
}
}
/**
* Executes Selector.selectNow() and returns
* the {@link Selector} to the cache
*/
public final static void selectNowAndReturnSelector(Selector s) {
try {
s.selectNow();
returnSelector(s);
} catch(IOException e) {
Logger logger = Controller.logger();
logger.log(Level.WARNING,
"Unexpected problem when releasing temporary Selector", e);
try {
s.close();
} catch(IOException ee) {
// We are not interested
}
try {
reimburseSelector();
} catch(IOException ee) {
logger.log(Level.WARNING,
"Problematic Selector could not be reimbursed!", ee);
}
}
}
/**
* Add Selector to the cache.
* This method could be called to reimberse a lost or problematic Selector.
*
* @throws java.io.IOException
*/
public final static void reimburseSelector() throws IOException {
returnSelector(createSelector());
}
/**
* Creeate Selector
* @return Selector
* @throws java.io.IOException
*/
protected static Selector createSelector() throws IOException {
return Selector.open();
}
/**
* Increase {@link Selector} pool size
*/
private static void grow(int size) throws IOException {
for(int i=0; i