MINA框架 中JAVA NIO处理主要逻辑的processor线程
下面是MINA接收非阻塞连接的主要逻辑
线程模型文章可以参考http://chinaestone.iteye.com/blog/435929
在Mina的NIO模式中有三种I/O工作线程（这三种线程模型只在NIO Socket中有效，在NIO数据包和虚拟管道中没有，也不需要配置）：
Acceptor thread
该线程的作用是接收客户端的连接，并将客户端的连接导入到I/O processor线程模型中。所谓的I/O processor线程模型就是Mina的I/O processor thread。Acceptor thread在调用了Acceptor.bind()方法后启动。每个Acceptor只能创建一个Acceptor thread，该线程模型不能配置，它由Mina自身提供。
Connector thread
该线程模型是客户端的连接线程模型，它的作用和Acceptor thread类似，它将客户端与服务器的连接导入到I/O processor线程模型中。同样地，该线程模型也是由Mina的客户端自动创建，该线程模型也不能进行配置。
I/O processor thread
该线程模型的主要作用就行接收和发送数据，所有的IO操作在服务器与客户端的连接建立后，所有的数据的接收和发送都是有该线程模型来负责的，知道客户端与服务器的连接关闭，该线程模型才停止工作。该线程模型可以由程序员根据需要进行配置。该线程模型默认的线程的数量为cpu的核数+1。若你的cpu为双核的，则你的I/O processor 线程的最大数量为3，同理若你的若你的cpu为四核的，那么你的I/O processor 线程的最大数量为5。
acceptor主要注册op_accept事件，只要收到连接事件，便初始化新会话并将会话交给processor处理后序的工作，这是两个不同的线程(池)
每个任务都是通过线程池来执行的
/**
* This class is called by the startupAcceptor() method and is
* placed into a NamePreservingRunnable class.
* It's a thread accepting incoming connections from clients.
* The loop is stopped when all the bound handlers are unbound.
*/
private class Acceptor implements Runnable {
public void run() {
assert (acceptorRef.get() == this);
int nHandles = 0;
while (selectable) {
try {
// Detect if we have some keys ready to be processed
// The select() will be woke up if some new connection
// have occurred, or if the selector has been explicitly
// woke up
int selected = select();
// this actually sets the selector to OP_ACCEPT,
// and binds to the port on which this class will
// listen on
nHandles += registerHandles();
// Now, if the number of registred handles is 0, we can
// quit the loop: we don't have any socket listening
// for incoming connection.
if (nHandles == 0) {
acceptorRef.set(null);
if (registerQueue.isEmpty() && cancelQueue.isEmpty()) {
assert (acceptorRef.get() != this);
break;
}
if (!acceptorRef.compareAndSet(null, this)) {
assert (acceptorRef.get() != this);
break;
}
assert (acceptorRef.get() == this);
}
if (selected > 0) {
// We have some connection request, let's process
// them here. 这里处理新来的连接，创建会话，然后交给IoProcessor线程池处理
processHandles(selectedHandles());
}
// check to see if any cancellation request has been made.
nHandles -= unregisterHandles();
} catch (ClosedSelectorException cse) {
// If the selector has been closed, we can exit the loop
break;
} catch (Throwable e) {
ExceptionMonitor.getInstance().exceptionCaught(e);
try {
Thread.sleep(1000);
} catch (InterruptedException e1) {
ExceptionMonitor.getInstance().exceptionCaught(e1);
}
}
}
// Cleanup all the processors, and shutdown the acceptor.
if (selectable && isDisposing()) {
selectable = false;
try {
if (createdProcessor) {
processor.dispose();
}
} finally {
try {
synchronized (disposalLock) {
if (isDisposing()) {
destroy();
}
}
} catch (Exception e) {
ExceptionMonitor.getInstance().exceptionCaught(e);
} finally {
disposalFuture.setDone();
}
}
}
}
/**
* This method will process new sessions for the Worker class. All
* keys that have had their status updates as per the Selector.selectedKeys()
* method will be processed here. Only keys that are ready to accept
* connections are handled here.
*
* Session objects are created by making new instances of SocketSessionImpl
* and passing the session object to the SocketIoProcessor class.
*/
@SuppressWarnings("unchecked")
private void processHandles(Iterator handles) throws Exception {
while (handles.hasNext()) {
H handle = handles.next();
handles.remove();
// Associates a new created connection to a processor,
// and get back a session对新来的连接创建一个新会话
S session = accept(processor, handle);
if (session == null) {
break;
}
initSession(session, null, null);
// add the session to the SocketIoProcessor
session.getProcessor().add(session);//会话交给SocketIoProcessor管理
}
}
} 这个线程主要处理Acceptor传递过来的会话的读、写、关闭事件，是AbstractPollingIoProcessor类的内部类
/**
* The main loop. This is the place in charge to poll负责轮询 the Selector, and to
* process the active sessions. It's done in
* - handle the newly created sessions
* -
*/
private class Processor implements Runnable {
public void run() {
assert (processorRef.get() == this);
int nSessions = 0;
lastIdleCheckTime = System.currentTimeMillis();
for (;;) {
try {
// This select has a timeout so that we can manage
// idle session when we get out of the select every
// second. (note : this is a hack to avoid creating
// a dedicated thread一个专门的线程).
long t0 = System.currentTimeMillis();
int selected = select(SELECT_TIMEOUT);
long t1 = System.currentTimeMillis();
long delta = (t1 - t0);
if ((selected == 0) && !wakeupCalled.get() && (delta < 100)) {
// Last chance : the select() may have been
// interrupted because we have had an closed channel.
if (isBrokenConnection()) {//由于有连接被关闭引起select中断
LOG.warn("Broken connection");
// we can reselect immediately
// set back the flag to false
wakeupCalled.getAndSet(false);
continue;
} else {
LOG.warn("Create a new selector. Selected is 0, delta = "
+ (t1 - t0));
// Ok, we are hit by the nasty epoll
// spinning.
// Basically, there is a race condition
// which causes(引起文件描述符关闭)a closing file descriptor not to be
// considered as available as a selected channel, but
// it stopped the select. The next time we will
// call select(), it will exit immediately for the same
// reason, and do so forever, consuming 100%
// CPU.
// We have to destroy the selector, and
// register all the socket on a new one.
registerNewSelector();
}
// Set back the flag to false
wakeupCalled.getAndSet(false);
// and continue the loop
continue;
}
// Manage newly created session first
nSessions += handleNewSessions();
updateTrafficMask();
// Now, if we have had some incoming or outgoing events,
// deal with them
if (selected > 0) {
//LOG.debug("Processing ..."); // This log hurts one of the MDCFilter test...
process();//处理读事件，并把新的需要写数据的会话添加到写队列中
}
// Write the pending requests
long currentTime = System.currentTimeMillis();
flush(currentTime);//写消息
// And manage removed sessions
nSessions -= removeSessions();
// Last, not least, send Idle events to the idle sessions
notifyIdleSessions(currentTime);
// Get a chance to exit the infinite loop if there are no
// more sessions on this Processor
if (nSessions == 0) {
processorRef.set(null);
if (newSessions.isEmpty() && isSelectorEmpty()) {
// newSessions.add() 在...之前precedes startupProcessor
assert (processorRef.get() != this);
break;
}
assert (processorRef.get() != this);
if (!processorRef.compareAndSet(null, this)) {
// startupProcessor won race, so must exit processor
assert (processorRef.get() != this);
break;
}
assert (processorRef.get() == this);
}
// Disconnect all sessions immediately if disposal has been
// requested so that we exit this loop eventually.
if (isDisposing()) {//关闭所有会话
for (Iterator i = allSessions(); i.hasNext();) {
scheduleRemove(i.next());//加入等关闭会话队列
}
wakeup();//中断select函数
}
} catch (ClosedSelectorException cse) {
// If the selector has been closed, we can exit the loop
break;
} catch (Throwable t) {
ExceptionMonitor.getInstance().exceptionCaught(t);
try {
Thread.sleep(1000);
} catch (InterruptedException e1) {
ExceptionMonitor.getInstance().exceptionCaught(e1);
}
}
}
try {
synchronized (disposalLock) {
if (disposing) {
doDispose();
}
}
} catch (Throwable t) {
ExceptionMonitor.getInstance().exceptionCaught(t);
} finally {
disposalFuture.setValue(true);
}
}
}