com.sun.grizzly.comet.concurrent.DefaultConcurrentCometHandler Maven / Gradle / Ivy
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package com.sun.grizzly.comet.concurrent;
import com.sun.grizzly.Controller;
import com.sun.grizzly.comet.CometEvent;
import com.sun.grizzly.comet.CometHandler;
import com.sun.grizzly.comet.DefaultNotificationHandler;
import java.io.IOException;
import java.util.LinkedList;
import java.util.logging.Logger;
/**
* we queue events in each comethandler to lower the probability
* that slow or massive IO for one comethandler severly delays events to others.
*
* only streaming mode can benefit from buffering messages like this.
* only 1 thread at a time is allowed to do IO,
* other threads put events in the queue and return to the thread pool.
*
* a thread initially calls enqueueEvent and stay there until there are no more
* events in the queue, calling the onEVent method in synchronized context for each Event.
*
* on IOE in onEvent we terminate.
* we have a limit, to keep memory usage under control.
*
* if queue limit is reached onQueueFull is called, and then we terminate.
*
*
* whats not optimal is that a worker thread is sticky to the client depending
* uppon available events in the handlers local queue,
* that can in theory allow a few clients to block all threads for extended time.
* that effect can make this implementation unusable depending on the scenario,
* its not a perfect design be any means.
*
* The potential improvement is that only 1 worker thread is tied up to a client instead of several
* being blocked by synchronized io wait for one comethandler .
*
* @author Gustav Trede
*/
public abstract class DefaultConcurrentCometHandler implements CometHandler{
protected final static Logger logger = Controller.logger();
/**
* used for preventing othe worker threads from the executor event queue from adding events
* to the comethandlers local queue or starting IO logic after shuttdown.
*/
private boolean shuttingdown;
/**
* max number of events to locally queue for this comethandler.
* (a global event queue normally exsists in form of a threadpool too)
*/
private final int messageQueueLimit;
/**
* current queue size
*/
private int queuesize;
/**
* true means that no thread is currently active on this comethandlers queue logic
*/
private boolean isreadyforwork = true;
/**
* todo replace with non array copying list for non rezing add situations,
* using internal index to keep track of state , not a linked list,
* it has too much overhead and eats memory.
*/
protected final LinkedList messageQueue = new LinkedList();
protected E attachment;
public DefaultConcurrentCometHandler() {
this(100);
}
/**
*
* @param messageQueueLimit
*/
public DefaultConcurrentCometHandler(int messageQueueLimit) {
this.messageQueueLimit = messageQueueLimit;
}
/**
* enqueues event if another thread is currently working on this handler.
* the first thread to start working will keep doing so until there are no
* further events in the internal queue.
*/
public void EnQueueEvent(CometEvent event){
synchronized(messageQueue){
if (!isreadyforwork){
if (!shuttingdown && queuesize < messageQueueLimit){
messageQueue.add(event);
queuesize++;
}
return;
}
isreadyforwork = false;
}
boolean queuefull = false;
while(!shuttingdown){
if(!event.getCometContext().isActive(this)){
shuttingdown = true;
return;
}
try{
//move synchronized outside the while loop ?
synchronized(this){
onEvent(event);
}
} catch (IOException ex) {
shuttingdown = true;
}finally{
if (shuttingdown){
event.getCometContext().resumeCometHandler(this);
return;
}
}
synchronized(messageQueue){
if (queuesize == messageQueueLimit){
queuefull = true;
}else
if (queuesize == 0){
isreadyforwork = true;
return;
}else{
event = messageQueue.poll();
queuesize--;
}
}
if (queuefull){
shuttingdown = true;
onQueueFull(event); //todo is onqeuefull needed ? or just terminate, it would simplify to just terminate =)
}
}
}
/**
* called in synchronized context.
* when the comethandler's local event queue is full.
* default impl resumes the comethandler
* @param event {@link CometEvent}
*/
public void onQueueFull(CometEvent event){
event.getCometContext().resumeCometHandler(this);
}
/**
* returns the attachment
*/
public E attachment() {
return attachment;
}
/**
* {@inheritDoc}
*/
//@Override // cant use override as long as we are compiling on jdk 1.5
public void attach(E attachment) {
this.attachment = attachment;
}
/**
* {@inheritDoc}
*
* default impl calls terminate()
*/
//@Override // cant use override as long as we are compiling on jdk 1.5
public void onInterrupt(CometEvent event) throws IOException {
terminate();
}
/**
* {@inheritDoc}
*
* default impl calls terminate()
*/
//@Override // cant use override as long as we are compiling on jdk 1.5
public void onTerminate(CometEvent event) throws IOException {
terminate();
}
/**
*
*/
protected void terminate(){
/* if (attachment() instanceof Closeable){
try {
((Closeable) attachment()).close();
} catch (IOException ex) { }
}*/
}
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