/*
* Copyright 2011 The Netty Project
*
* The Netty Project licenses this file to you under the Apache License,
* version 2.0 (the "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*/
package org.jboss.netty.channel.socket.nio;
import static org.jboss.netty.channel.Channels.*;
import java.io.IOException;
import java.net.SocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.AsynchronousCloseException;
import java.nio.channels.CancelledKeyException;
import java.nio.channels.ClosedChannelException;
import java.nio.channels.DatagramChannel;
import java.nio.channels.NotYetBoundException;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.util.Iterator;
import java.util.Queue;
import java.util.Set;
import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import org.jboss.netty.buffer.ChannelBufferFactory;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelException;
import org.jboss.netty.channel.ChannelFuture;
import org.jboss.netty.channel.MessageEvent;
import org.jboss.netty.channel.ReceiveBufferSizePredictor;
import org.jboss.netty.channel.socket.nio.SocketSendBufferPool.SendBuffer;
import org.jboss.netty.logging.InternalLogger;
import org.jboss.netty.logging.InternalLoggerFactory;
import org.jboss.netty.util.ThreadRenamingRunnable;
import org.jboss.netty.util.internal.QueueFactory;
/**
* A class responsible for registering channels with {@link Selector}.
* It also implements the {@link Selector} loop.
*/
class NioDatagramWorker implements Runnable {
/**
* Internal Netty logger.
*/
private static final InternalLogger logger = InternalLoggerFactory
.getInstance(NioDatagramWorker.class);
/**
* This id of this worker.
*/
private final int id;
/**
* This id of the NioDatagramPipelineSink.
*/
private final int bossId;
/**
* Executor used to execute {@link Runnable}s such as
* {@link ChannelRegistionTask}.
*/
private final Executor executor;
/**
* Boolean to indicate if this worker has been started.
*/
private boolean started;
/**
* If this worker has been started thread will be a reference to the thread
* used when starting. i.e. the current thread when the run method is executed.
*/
private volatile Thread thread;
/**
* The NIO {@link Selector}.
*/
volatile Selector selector;
/**
* Boolean that controls determines if a blocked Selector.select should
* break out of its selection process. In our case we use a timeone for
* the select method and the select method will block for that time unless
* waken up.
*/
private final AtomicBoolean wakenUp = new AtomicBoolean();
/**
* Lock for this workers Selector.
*/
private final ReadWriteLock selectorGuard = new ReentrantReadWriteLock();
/**
* Monitor object used to synchronize selector open/close.
*/
private final Object startStopLock = new Object();
/**
* Queue of {@link ChannelRegistionTask}s
*/
private final Queue<Runnable> registerTaskQueue = QueueFactory.createQueue(Runnable.class);;
/**
* Queue of WriteTasks
*/
private final Queue<Runnable> writeTaskQueue = QueueFactory.createQueue(Runnable.class);
private volatile int cancelledKeys; // should use AtomicInteger but we just need approximation
private final SocketSendBufferPool sendBufferPool = new SocketSendBufferPool();
/**
* Sole constructor.
*
* @param bossId This id of the NioDatagramPipelineSink
* @param id The id of this worker
* @param executor the {@link Executor} used to execute {@link Runnable}s
* such as {@link ChannelRegistionTask}
*/
NioDatagramWorker(final int bossId, final int id, final Executor executor) {
this.bossId = bossId;
this.id = id;
this.executor = executor;
}
/**
* Registers the passed-in channel with a selector.
*
* @param channel the channel to register
* @param future the {@link ChannelFuture} that has to be notified on
* completion
*/
void register(final NioDatagramChannel channel, final ChannelFuture future) {
final Runnable channelRegTask = new ChannelRegistionTask(channel,
future);
Selector selector;
synchronized (startStopLock) {
if (!started) {
// Open a selector if this worker didn't start yet.
try {
this.selector = selector = Selector.open();
} catch (final Throwable t) {
throw new ChannelException("Failed to create a selector.",
t);
}
boolean success = false;
try {
// Start the main selector loop. See run() for details.
executor.execute(new ThreadRenamingRunnable(this,
"New I/O datagram worker #" + bossId + "'-'" + id));
success = true;
} finally {
if (!success) {
try {
// Release the Selector if the execution fails.
selector.close();
} catch (final Throwable t) {
logger.warn("Failed to close a selector.", t);
}
this.selector = selector = null;
// The method will return to the caller at this point.
}
}
} else {
// Use the existing selector if this worker has been started.
selector = this.selector;
}
assert selector != null && selector.isOpen();
started = true;
// "Add" the registration task to the register task queue.
boolean offered = registerTaskQueue.offer(channelRegTask);
assert offered;
}
if (wakenUp.compareAndSet(false, true)) {
selector.wakeup();
}
}
/**
* Selector loop.
*/
public void run() {
// Store a ref to the current thread.
thread = Thread.currentThread();
final Selector selector = this.selector;
boolean shutdown = false;
for (;;) {
wakenUp.set(false);
if (NioProviderMetadata.CONSTRAINT_LEVEL != 0) {
selectorGuard.writeLock().lock();
// This empty synchronization block prevents the selector from acquiring its lock.
selectorGuard.writeLock().unlock();
}
try {
SelectorUtil.select(selector);
// 'wakenUp.compareAndSet(false, true)' is always evaluated
// before calling 'selector.wakeup()' to reduce the wake-up
// overhead. (Selector.wakeup() is an expensive operation.)
//
// However, there is a race condition in this approach.
// The race condition is triggered when 'wakenUp' is set to
// true too early.
//
// 'wakenUp' is set to true too early if:
// 1) Selector is waken up between 'wakenUp.set(false)' and
// 'selector.select(...)'. (BAD)
// 2) Selector is waken up between 'selector.select(...)' and
// 'if (wakenUp.get()) { ... }'. (OK)
//
// In the first case, 'wakenUp' is set to true and the
// following 'selector.select(...)' will wake up immediately.
// Until 'wakenUp' is set to false again in the next round,
// 'wakenUp.compareAndSet(false, true)' will fail, and therefore
// any attempt to wake up the Selector will fail, too, causing
// the following 'selector.select(...)' call to block
// unnecessarily.
//
// To fix this problem, we wake up the selector again if wakenUp
// is true immediately after selector.select(...).
// It is inefficient in that it wakes up the selector for both
// the first case (BAD - wake-up required) and the second case
// (OK - no wake-up required).
if (wakenUp.get()) {
selector.wakeup();
}
cancelledKeys = 0;
processRegisterTaskQueue();
processWriteTaskQueue();
processSelectedKeys(selector.selectedKeys());
// Exit the loop when there's nothing to handle (the registered
// key set is empty.
// The shutdown flag is used to delay the shutdown of this
// loop to avoid excessive Selector creation when
// connections are registered in a one-by-one manner instead of
// concurrent manner.
if (selector.keys().isEmpty()) {
if (shutdown || executor instanceof ExecutorService &&
((ExecutorService) executor).isShutdown()) {
synchronized (startStopLock) {
if (registerTaskQueue.isEmpty() &&
selector.keys().isEmpty()) {
started = false;
try {
selector.close();
} catch (IOException e) {
logger.warn("Failed to close a selector.",
e);
} finally {
this.selector = null;
}
break;
} else {
shutdown = false;
}
}
} else {
// Give one more second.
shutdown = true;
}
} else {
shutdown = false;
}
} catch (Throwable t) {
logger.warn("Unexpected exception in the selector loop.", t);
// Prevent possible consecutive immediate failures that lead to
// excessive CPU consumption.
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
// Ignore.
}
}
}
}
/**
* Will go through all the {@link ChannelRegistionTask}s in the
* task queue and run them (registering them).
*/
private void processRegisterTaskQueue() throws IOException {
for (;;) {
final Runnable task = registerTaskQueue.poll();
if (task == null) {
break;
}
task.run();
cleanUpCancelledKeys();
}
}
/**
* Will go through all the WriteTasks and run them.
*/
private void processWriteTaskQueue() throws IOException {
for (;;) {
final Runnable task = writeTaskQueue.poll();
if (task == null) {
break;
}
task.run();
cleanUpCancelledKeys();
}
}
private void processSelectedKeys(final Set<SelectionKey> selectedKeys) throws IOException {
for (Iterator<SelectionKey> i = selectedKeys.iterator(); i.hasNext();) {
SelectionKey k = i.next();
i.remove();
try {
int readyOps = k.readyOps();
if ((readyOps & SelectionKey.OP_READ) != 0 || readyOps == 0) {
if (!read(k)) {
// Connection already closed - no need to handle write.
continue;
}
}
if ((readyOps & SelectionKey.OP_WRITE) != 0) {
writeFromSelectorLoop(k);
}
} catch (CancelledKeyException e) {
close(k);
}
if (cleanUpCancelledKeys()) {
break; // Break the loop to avoid ConcurrentModificationException
}
}
}
private boolean cleanUpCancelledKeys() throws IOException {
if (cancelledKeys >= NioWorker.CLEANUP_INTERVAL) {
cancelledKeys = 0;
selector.selectNow();
return true;
}
return false;
}
/**
* Read is called when a Selector has been notified that the underlying channel
* was something to be read. The channel would previously have registered its interest
* in read operations.
*
* @param key The selection key which contains the Selector registration information.
*/
private boolean read(final SelectionKey key) {
final NioDatagramChannel channel = (NioDatagramChannel) key.attachment();
ReceiveBufferSizePredictor predictor =
channel.getConfig().getReceiveBufferSizePredictor();
final ChannelBufferFactory bufferFactory = channel.getConfig().getBufferFactory();
final DatagramChannel nioChannel = (DatagramChannel) key.channel();
// Allocating a non-direct buffer with a max udp packge size.
// Would using a direct buffer be more efficient or would this negatively
// effect performance, as direct buffer allocation has a higher upfront cost
// where as a ByteBuffer is heap allocated.
final ByteBuffer byteBuffer = ByteBuffer.allocate(
predictor.nextReceiveBufferSize()).order(bufferFactory.getDefaultOrder());
boolean failure = true;
SocketAddress remoteAddress = null;
try {
// Receive from the channel in a non blocking mode. We have already been notified that
// the channel is ready to receive.
remoteAddress = nioChannel.receive(byteBuffer);
failure = false;
} catch (ClosedChannelException e) {
// Can happen, and does not need a user attention.
} catch (Throwable t) {
fireExceptionCaught(channel, t);
}
if (remoteAddress != null) {
// Flip the buffer so that we can wrap it.
byteBuffer.flip();
int readBytes = byteBuffer.remaining();
if (readBytes > 0) {
// Update the predictor.
predictor.previousReceiveBufferSize(readBytes);
// Notify the interested parties about the newly arrived message.
fireMessageReceived(
channel, bufferFactory.getBuffer(byteBuffer), remoteAddress);
}
}
if (failure) {
key.cancel(); // Some JDK implementations run into an infinite loop without this.
close(channel, succeededFuture(channel));
return false;
}
return true;
}
private void close(SelectionKey k) {
final NioDatagramChannel ch = (NioDatagramChannel) k.attachment();
close(ch, succeededFuture(ch));
}
void writeFromUserCode(final NioDatagramChannel channel) {
/*
* Note that we are not checking if the channel is connected. Connected
* has a different meaning in UDP and means that the channels socket is
* configured to only send and receive from a given remote peer.
*/
if (!channel.isBound()) {
cleanUpWriteBuffer(channel);
return;
}
if (scheduleWriteIfNecessary(channel)) {
return;
}
// From here, we are sure Thread.currentThread() == workerThread.
if (channel.writeSuspended) {
return;
}
if (channel.inWriteNowLoop) {
return;
}
write0(channel);
}
void writeFromTaskLoop(final NioDatagramChannel ch) {
if (!ch.writeSuspended) {
write0(ch);
}
}
void writeFromSelectorLoop(final SelectionKey k) {
NioDatagramChannel ch = (NioDatagramChannel) k.attachment();
ch.writeSuspended = false;
write0(ch);
}
private boolean scheduleWriteIfNecessary(final NioDatagramChannel channel) {
final Thread workerThread = thread;
if (workerThread == null || Thread.currentThread() != workerThread) {
if (channel.writeTaskInTaskQueue.compareAndSet(false, true)) {
// "add" the channels writeTask to the writeTaskQueue.
boolean offered = writeTaskQueue.offer(channel.writeTask);
assert offered;
}
final Selector selector = this.selector;
if (selector != null) {
if (wakenUp.compareAndSet(false, true)) {
selector.wakeup();
}
}
return true;
}
return false;
}
private void write0(final NioDatagramChannel channel) {
boolean addOpWrite = false;
boolean removeOpWrite = false;
long writtenBytes = 0;
final SocketSendBufferPool sendBufferPool = this.sendBufferPool;
final DatagramChannel ch = channel.getDatagramChannel();
final Queue<MessageEvent> writeBuffer = channel.writeBufferQueue;
final int writeSpinCount = channel.getConfig().getWriteSpinCount();
synchronized (channel.writeLock) {
// inform the channel that write is in-progress
channel.inWriteNowLoop = true;
// loop forever...
for (;;) {
MessageEvent evt = channel.currentWriteEvent;
SendBuffer buf;
if (evt == null) {
if ((channel.currentWriteEvent = evt = writeBuffer.poll()) == null) {
removeOpWrite = true;
channel.writeSuspended = false;
break;
}
channel.currentWriteBuffer = buf = sendBufferPool.acquire(evt.getMessage());
} else {
buf = channel.currentWriteBuffer;
}
try {
long localWrittenBytes = 0;
SocketAddress raddr = evt.getRemoteAddress();
if (raddr == null) {
for (int i = writeSpinCount; i > 0; i --) {
localWrittenBytes = buf.transferTo(ch);
if (localWrittenBytes != 0) {
writtenBytes += localWrittenBytes;
break;
}
if (buf.finished()) {
break;
}
}
} else {
for (int i = writeSpinCount; i > 0; i --) {
localWrittenBytes = buf.transferTo(ch, raddr);
if (localWrittenBytes != 0) {
writtenBytes += localWrittenBytes;
break;
}
if (buf.finished()) {
break;
}
}
}
if (localWrittenBytes > 0 || buf.finished()) {
// Successful write - proceed to the next message.
buf.release();
ChannelFuture future = evt.getFuture();
channel.currentWriteEvent = null;
channel.currentWriteBuffer = null;
evt = null;
buf = null;
future.setSuccess();
} else {
// Not written at all - perhaps the kernel buffer is full.
addOpWrite = true;
channel.writeSuspended = true;
break;
}
} catch (final AsynchronousCloseException e) {
// Doesn't need a user attention - ignore.
} catch (final Throwable t) {
buf.release();
ChannelFuture future = evt.getFuture();
channel.currentWriteEvent = null;
channel.currentWriteBuffer = null;
buf = null;
evt = null;
future.setFailure(t);
fireExceptionCaught(channel, t);
}
}
channel.inWriteNowLoop = false;
// Initially, the following block was executed after releasing
// the writeLock, but there was a race condition, and it has to be
// executed before releasing the writeLock:
//
// https://issues.jboss.org/browse/NETTY-410
//
if (addOpWrite) {
setOpWrite(channel);
} else if (removeOpWrite) {
clearOpWrite(channel);
}
}
fireWriteComplete(channel, writtenBytes);
}
private void setOpWrite(final NioDatagramChannel channel) {
Selector selector = this.selector;
SelectionKey key = channel.getDatagramChannel().keyFor(selector);
if (key == null) {
return;
}
if (!key.isValid()) {
close(key);
return;
}
// interestOps can change at any time and at any thread.
// Acquire a lock to avoid possible race condition.
synchronized (channel.interestOpsLock) {
int interestOps = channel.getRawInterestOps();
if ((interestOps & SelectionKey.OP_WRITE) == 0) {
interestOps |= SelectionKey.OP_WRITE;
key.interestOps(interestOps);
channel.setRawInterestOpsNow(interestOps);
}
}
}
private void clearOpWrite(NioDatagramChannel channel) {
Selector selector = this.selector;
SelectionKey key = channel.getDatagramChannel().keyFor(selector);
if (key == null) {
return;
}
if (!key.isValid()) {
close(key);
return;
}
// interestOps can change at any time and at any thread.
// Acquire a lock to avoid possible race condition.
synchronized (channel.interestOpsLock) {
int interestOps = channel.getRawInterestOps();
if ((interestOps & SelectionKey.OP_WRITE) != 0) {
interestOps &= ~SelectionKey.OP_WRITE;
key.interestOps(interestOps);
channel.setRawInterestOpsNow(interestOps);
}
}
}
static void disconnect(NioDatagramChannel channel, ChannelFuture future) {
boolean connected = channel.isConnected();
try {
channel.getDatagramChannel().disconnect();
future.setSuccess();
if (connected) {
fireChannelDisconnected(channel);
}
} catch (Throwable t) {
future.setFailure(t);
fireExceptionCaught(channel, t);
}
}
void close(final NioDatagramChannel channel,
final ChannelFuture future) {
boolean connected = channel.isConnected();
boolean bound = channel.isBound();
try {
channel.getDatagramChannel().close();
cancelledKeys ++;
if (channel.setClosed()) {
future.setSuccess();
if (connected) {
fireChannelDisconnected(channel);
}
if (bound) {
fireChannelUnbound(channel);
}
cleanUpWriteBuffer(channel);
fireChannelClosed(channel);
} else {
future.setSuccess();
}
} catch (Throwable t) {
future.setFailure(t);
fireExceptionCaught(channel, t);
}
}
private void cleanUpWriteBuffer(final NioDatagramChannel channel) {
Exception cause = null;
boolean fireExceptionCaught = false;
// Clean up the stale messages in the write buffer.
synchronized (channel.writeLock) {
MessageEvent evt = channel.currentWriteEvent;
if (evt != null) {
// Create the exception only once to avoid the excessive overhead
// caused by fillStackTrace.
if (channel.isOpen()) {
cause = new NotYetBoundException();
} else {
cause = new ClosedChannelException();
}
ChannelFuture future = evt.getFuture();
channel.currentWriteBuffer.release();
channel.currentWriteBuffer = null;
channel.currentWriteEvent = null;
evt = null;
future.setFailure(cause);
fireExceptionCaught = true;
}
Queue<MessageEvent> writeBuffer = channel.writeBufferQueue;
if (!writeBuffer.isEmpty()) {
// Create the exception only once to avoid the excessive overhead
// caused by fillStackTrace.
if (cause == null) {
if (channel.isOpen()) {
cause = new NotYetBoundException();
} else {
cause = new ClosedChannelException();
}
}
for (;;) {
evt = writeBuffer.poll();
if (evt == null) {
break;
}
evt.getFuture().setFailure(cause);
fireExceptionCaught = true;
}
}
}
if (fireExceptionCaught) {
fireExceptionCaught(channel, cause);
}
}
void setInterestOps(final NioDatagramChannel channel,
ChannelFuture future, int interestOps) {
boolean changed = false;
try {
// interestOps can change at any time and by any thread.
// Acquire a lock to avoid possible race condition.
synchronized (channel.interestOpsLock) {
final Selector selector = this.selector;
final SelectionKey key = channel.getDatagramChannel().keyFor(selector);
if (key == null || selector == null) {
// Not registered to the worker yet.
// Set the rawInterestOps immediately; RegisterTask will pick it up.
channel.setRawInterestOpsNow(interestOps);
return;
}
// Override OP_WRITE flag - a user cannot change this flag.
interestOps &= ~Channel.OP_WRITE;
interestOps |= channel.getRawInterestOps() & Channel.OP_WRITE;
switch (NioProviderMetadata.CONSTRAINT_LEVEL) {
case 0:
if (channel.getRawInterestOps() != interestOps) {
// Set the interesteOps on the SelectionKey
key.interestOps(interestOps);
// If the worker thread (the one that that might possibly be blocked
// in a select() call) is not the thread executing this method wakeup
// the select() operation.
if (Thread.currentThread() != thread &&
wakenUp.compareAndSet(false, true)) {
selector.wakeup();
}
changed = true;
}
break;
case 1:
case 2:
if (channel.getRawInterestOps() != interestOps) {
if (Thread.currentThread() == thread) {
// Going to set the interestOps from the same thread.
// Set the interesteOps on the SelectionKey
key.interestOps(interestOps);
changed = true;
} else {
// Going to set the interestOps from a different thread
// and some old provides will need synchronization.
selectorGuard.readLock().lock();
try {
if (wakenUp.compareAndSet(false, true)) {
selector.wakeup();
}
key.interestOps(interestOps);
changed = true;
} finally {
selectorGuard.readLock().unlock();
}
}
}
break;
default:
throw new Error();
}
if (changed) {
channel.setRawInterestOpsNow(interestOps);
}
}
future.setSuccess();
if (changed) {
fireChannelInterestChanged(channel);
}
} catch (final CancelledKeyException e) {
// setInterestOps() was called on a closed channel.
ClosedChannelException cce = new ClosedChannelException();
future.setFailure(cce);
fireExceptionCaught(channel, cce);
} catch (final Throwable t) {
future.setFailure(t);
fireExceptionCaught(channel, t);
}
}
/**
* RegisterTask is a task responsible for registering a channel with a
* selector.
*/
private final class ChannelRegistionTask implements Runnable {
private final NioDatagramChannel channel;
private final ChannelFuture future;
ChannelRegistionTask(final NioDatagramChannel channel,
final ChannelFuture future) {
this.channel = channel;
this.future = future;
}
/**
* This runnable's task. Does the actual registering by calling the
* underlying DatagramChannels peer DatagramSocket register method.
*/
public void run() {
final SocketAddress localAddress = channel.getLocalAddress();
if (localAddress == null) {
if (future != null) {
future.setFailure(new ClosedChannelException());
}
close(channel, succeededFuture(channel));
return;
}
try {
synchronized (channel.interestOpsLock) {
channel.getDatagramChannel().register(
selector, channel.getRawInterestOps(), channel);
}
if (future != null) {
future.setSuccess();
}
} catch (final ClosedChannelException e) {
if (future != null) {
future.setFailure(e);
}
close(channel, succeededFuture(channel));
throw new ChannelException(
"Failed to register a socket to the selector.", e);
}
}
}
}