Tomcat NIO源代码分析(二) -- Poller
接着上面的流程，现在请求到了Poller的#register()方法。
public
void
register(
final
NioChannel socket)
{
socket.setPoller( this ); // KeyAttachment是对NioChannel信息的包装，同样是非GC KeyAttachment key = keyCache.poll(); final KeyAttachment ka = key != null ? key : new KeyAttachment(socket); ka.reset( this , socket, getSocketProperties().getSoTimeout()); ka.setKeepAliveLeft(NioEndpoint. this .getMaxKeepAliveRequests()); // PollerEvent的初始化，非GC Again PollerEvent r = eventCache.poll(); // this is what OP_REGISTER turns into. // 读取数据的事件 ka.interestOps(SelectionKey.OP_READ); if (r == null ) r = new PollerEvent(socket, ka, OP_REGISTER); else r.reset(socket, ka, OP_REGISTER); // 把事件加到Poller addEvent(r);
}
public
void
addEvent(Runnable event)
{ // 把事件加入到队列中 events.offer(event); // ++wakeupCounter if (wakeupCounter.incrementAndGet() == 0 ) selector.wakeup(); }
其实也挺好懂的，就是把NioChannel作为OP_REGISTER事件注册到Poller，这样在Poller的#run()方法中就可以对加入Poller的事件进行处理了。
public
void
run()
{
while (running) {
try { while (paused && ( ! close)) { try { Thread.sleep( 100 ); } catch (InterruptedException e) { // Ignore 
} } boolean hasEvents = false ; hasEvents = (hasEvents | events()); // Time to terminate? if (close) { timeout( 0 , false ); break ; } try { if ( ! close) { if (wakeupCounter.get() > 0 ) { // 立刻返回 I/O 就绪的那些通道的键 keyCount = selector.selectNow(); } else { keyCount = selector.keys().size(); // 这里把wakeupCounter设成-1，在addEvent的时候就会唤醒selector wakeupCounter.set( - 1 ); // 使用阻塞的方式 keyCount = selector.select(selectorTimeout); } wakeupCounter.set( 0 ); } if (close) { timeout( 0 , false ); selector.close(); break ; } } catch (NullPointerException x) { // sun bug 5076772 on windows JDK 1.5 if (log.isDebugEnabled()) log.debug( " Possibly encountered sun bug 5076772 on windows JDK 1.5 " , x); if (wakeupCounter == null || selector == null ) throw x; continue ; } catch (CancelledKeyException x) { // sun bug 5076772 on windows JDK 1.5 if (log.isDebugEnabled()) log.debug( " Possibly encountered sun bug 5076772 on windows JDK 1.5 " , x); if (wakeupCounter == null || selector == null ) throw x; continue ; } catch (Throwable x) { ExceptionUtils.handleThrowable(x); log.error( "" , x); continue ; } // either we timed out or we woke up, process events first if (keyCount == 0 ) hasEvents = (hasEvents | events()); Iterator < SelectionKey > iterator = keyCount > 0 ? selector.selectedKeys().iterator() : null ; // Walk through the collection of ready keys and dispatch // any active event. while (iterator != null && iterator.hasNext()) { SelectionKey sk = iterator.next(); // 这里的KeyAttachment实在#register()方法中注册的 KeyAttachment attachment = (KeyAttachment) sk.attachment(); attachment.access(); iterator.remove(); // 继续流程 processKey(sk, attachment); } // while // process timeouts timeout(keyCount, hasEvents); if (oomParachute > 0 && oomParachuteData == null ) checkParachute(); } catch (OutOfMemoryError oom) { try { oomParachuteData = null ; releaseCaches(); log.error( "" , oom); } catch (Throwable oomt) { try { System.err.println(oomParachuteMsg); oomt.printStackTrace(); } catch (Throwable letsHopeWeDontGetHere) { ExceptionUtils.handleThrowable(letsHopeWeDontGetHere); } } } } // while synchronized ( this ) { this .notifyAll(); } stopLatch.countDown(); }
这个方法有2个方法需要关注一下：#events()和#processKey()：
public
boolean
events()
{ boolean result = false ; // synchronized (events) { Runnable r = null ; // 返回是事件队列中是否有事件 result = (events.size() > 0 ); while ((r = events.poll()) != null ) { try { // 执行KeyEvent的#run() r.run(); if (r instanceof PollerEvent) { ((PollerEvent) r).reset(); // 对KeyEvent进行回收 eventCache.offer((PollerEvent) r); } } catch (Throwable x) { log.error( "" , x); } } // events.clear(); // } return result; }
这里执行了SocketChannel对应的KeyEvent的#run()方法，在这个方法里给SocketChannel注册了OP_READ：
public
void
run()
{ if (interestOps == OP_REGISTER) { try { // 给SocketChannel注册OP_READ socket.getIOChannel().register(socket.getPoller().getSelector(), SelectionKey.OP_READ, key); } catch (Exception x) { log.error( "" , x); } } else { // 这里应该是对comet进行支持的，暂时先不看 ...... } // end if }
//
run
第二个是#processKey()方法，里边的很多流程我现在不是很关心，都略去了，
protected
boolean
processKey(SelectionKey sk, KeyAttachment attachment)
{ boolean result = true ; try { if (close) { cancelledKey(sk, SocketStatus.STOP, false ); } else if (sk.isValid() && attachment != null ) { attachment.access(); // make sure we don't time out valid sockets sk.attach(attachment); // cant remember why this is here NioChannel channel = attachment.getChannel(); if (sk.isReadable() || sk.isWritable()) { if (attachment.getSendfileData() != null ) { processSendfile(sk, attachment, true , false ); } else if (attachment.getComet()) { // 这里应该是对comet的支持 ...... } else { // 这个分支是现在比较关心的 if (isWorkerAvailable()) { // 这个好像还没实现 // 这个#unreg()很巧妙，防止了通道对同一个事件不断select的问题 unreg(sk, attachment, sk.readyOps()); boolean close = ( ! processSocket(channel, null , true )); color: #000
1
顶
顶
4
踩
踩
分享到：
评论