/*
* Licensed 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 com.ok2c.lightnio.impl;
import java.io.IOException;
import java.io.InterruptedIOException;
import java.net.Socket;
import java.nio.channels.Channel;
import java.nio.channels.ClosedChannelException;
import java.nio.channels.ClosedSelectorException;
import java.nio.channels.SelectableChannel;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.util.ArrayList;
import java.util.Date;
import java.util.Iterator;
import java.util.List;
import java.util.Set;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.atomic.AtomicInteger;
import com.ok2c.lightnio.IOEventDispatch;
import com.ok2c.lightnio.IOReactor;
import com.ok2c.lightnio.IOReactorException;
import com.ok2c.lightnio.IOReactorExceptionHandler;
import com.ok2c.lightnio.IOReactorStatus;
/**
* Generic implementation of {@link IOReactor} that can run multiple
* {@link BaseIOReactor} instance in separate worker threads and distribute
* newly created I/O session equally across those I/O reactors for a more
* optimal resource utilization and a better I/O performance. Usually it is
* recommended to have one worker I/O reactor per physical CPU core.
* <p>
* <strong>Important note about exception handling</strong>
* <p>
* Protocol specific exceptions as well as those I/O exceptions thrown in the
* course of interaction with the session's channel are to be expected are to be
* dealt with by specific protocol handlers. These exceptions may result in
* termination of an individual session but should not affect the I/O reactor
* and all other active sessions. There are situations, however, when the I/O
* reactor itself encounters an internal problem such as an I/O exception in
* the underlying NIO classes or an unhandled runtime exception. Those types of
* exceptions are usually fatal and will cause the I/O reactor to shut down
* automatically.
* <p>
* There is a possibility to override this behavior and prevent I/O reactors
* from shutting down automatically in case of a runtime exception or an I/O
* exception in internal classes. This can be accomplished by providing a custom
* implementation of the {@link IOReactorExceptionHandler} interface.
* <p>
* If an I/O reactor is unable to automatically recover from an I/O or a runtime
* exception it will enter the shutdown mode. First off, it cancel all pending
* new session requests. Then it will attempt to close all active I/O sessions
* gracefully giving them some time to flush pending output data and terminate
* cleanly. Lastly, it will forcibly shut down those I/O sessions that still
* remain active after the grace period. This is a fairly complex process, where
* many things can fail at the same time and many different exceptions can be
* thrown in the course of the shutdown process. The I/O reactor will record all
* exceptions thrown during the shutdown process, including the original one
* that actually caused the shutdown in the first place, in an audit log. One
* can obtain the audit log using {@link #getAuditLog()}, examine exceptions
* thrown by the I/O reactor prior and in the course of the reactor shutdown
* and decide whether it is safe to restart the I/O reactor.
*/
public abstract class AbstractMultiworkerIOReactor implements IOReactor {
protected volatile IOReactorStatus status;
protected final Selector selector;
protected final long selectTimeout;
protected final boolean interestOpsQueueing;
protected final long gracePeriod;
protected final boolean tcpNoDelay;
protected final int soLinger;
private final int workerCount;
private final ThreadFactory threadFactory;
private final BaseIOReactor[] dispatchers;
private final Worker[] workers;
private final Thread[] threads;
private final Object statusLock;
protected IOReactorExceptionHandler exceptionHandler;
protected List<ExceptionEvent> auditLog;
private int currentWorker = 0;
/**
* Creates an instance of AbstractMultiworkerIOReactor.
*
* @param config the configuration object.
* @param threadFactory the factory to create threads.
* Can be <code>null</code>.
* @throws IOReactorException in case if a non-recoverable I/O error.
*/
public AbstractMultiworkerIOReactor(
final IOReactorConfig config,
final ThreadFactory threadFactory) throws IOReactorException {
super();
if (config == null) {
throw new IllegalArgumentException("Configuration may not be null");
}
try {
this.selector = Selector.open();
} catch (IOException ex) {
throw new IOReactorException("Failure opening selector", ex);
}
this.workerCount = config.getWorkerCount();
this.selectTimeout = config.getSelectInterval();
this.interestOpsQueueing = config.isInterestOpsQueueing();
this.gracePeriod = config.getGracePeriod();
this.tcpNoDelay = config.isTcpNoDelay();
this.soLinger = config.getSoLinger();
this.statusLock = new Object();
if (threadFactory != null) {
this.threadFactory = threadFactory;
} else {
this.threadFactory = new DefaultThreadFactory();
}
this.dispatchers = new BaseIOReactor[workerCount];
this.workers = new Worker[workerCount];
this.threads = new Thread[workerCount];
this.status = IOReactorStatus.INACTIVE;
}
public IOReactorStatus getStatus() {
return this.status;
}
/**
* Returns the audit log containing exceptions thrown by the I/O reactor
* prior and in the course of the reactor shutdown.
*
* @return audit log.
*/
public synchronized List<ExceptionEvent> getAuditLog() {
if (this.auditLog != null) {
return new ArrayList<ExceptionEvent>(this.auditLog);
} else {
return null;
}
}
/**
* Adds the given {@link Throwable} object with the given time stamp
* to the audit log.
*
* @param ex the exception thrown by the I/O reactor.
* @param timestamp the time stamp of the exception. Can be
* <code>null</code> in which case the current date / time will be used.
*/
protected synchronized void addExceptionEvent(final Throwable ex, Date timestamp) {
if (ex == null) {
return;
}
if (timestamp == null) {
timestamp = new Date();
}
if (this.auditLog == null) {
this.auditLog = new ArrayList<ExceptionEvent>();
}
this.auditLog.add(new ExceptionEvent(ex, timestamp));
}
/**
* Adds the given {@link Throwable} object to the audit log.
*
* @param ex the exception thrown by the I/O reactor.
*/
protected void addExceptionEvent(final Throwable ex) {
addExceptionEvent(ex, null);
}
/**
* Sets exception handler for this I/O reactor.
*
* @param exceptionHandler the exception handler.
*/
public void setExceptionHandler(final IOReactorExceptionHandler exceptionHandler) {
this.exceptionHandler = exceptionHandler;
}
/**
* Triggered to process I/O events registered by the main {@link Selector}.
* <p>
* Super-classes can implement this method to react to the event.
*
* @param count event count.
* @throws IOReactorException in case if a non-recoverable I/O error.
*/
protected abstract void processEvents(int count) throws IOReactorException;
/**
* Triggered to cancel pending session requests.
* <p>
* Super-classes can implement this method to react to the event.
*
* @throws IOReactorException in case if a non-recoverable I/O error.
*/
protected abstract void cancelRequests() throws IOReactorException;
/**
* Activates the main I/O reactor as well as all worker I/O reactors.
* The I/O main reactor will start reacting to I/O events and triggering
* notification methods. The worker I/O reactor in their turn will start
* reacting to I/O events and dispatch I/O event notifications to the given
* {@link IOEventDispatch} interface.
* <p>
* This method will enter the infinite I/O select loop on
* the {@link Selector} instance associated with this I/O reactor and used
* to manage creation of new I/O channels. Once a new I/O channel has been
* created the processing of I/O events on that channel will be delegated
* to one of the worker I/O reactors.
* <p>
* The method will remain blocked unto the I/O reactor is shut down or the
* execution thread is interrupted.
* <p>
* The following HTTP parameters affect execution of this method:
* <p>
* The {@link IOReactorConfig#getSelectInterval()} parameter determines the
* time interval in milliseconds at which the I/O reactor wakes up to check
* for timed out sessions and session requests.
*
* @see #processEvents(int)
* @see #cancelRequests()
*
* @throws InterruptedIOException if the dispatch thread is interrupted.
* @throws IOReactorException in case if a non-recoverable I/O error.
*/
public void execute(
final IOEventDispatch eventDispatch) throws InterruptedIOException, IOReactorException {
if (eventDispatch == null) {
throw new IllegalArgumentException("Event dispatcher may not be null");
}
synchronized (this.statusLock) {
if (this.status.compareTo(IOReactorStatus.SHUTDOWN_REQUEST) >= 0) {
this.status = IOReactorStatus.SHUT_DOWN;
this.statusLock.notifyAll();
return;
}
if (this.status.compareTo(IOReactorStatus.INACTIVE) != 0) {
throw new IllegalStateException("Illegal state: " + this.status);
}
this.status = IOReactorStatus.ACTIVE;
// Start I/O dispatchers
for (int i = 0; i < this.dispatchers.length; i++) {
BaseIOReactor dispatcher = new BaseIOReactor(this.selectTimeout, this.interestOpsQueueing);
dispatcher.setExceptionHandler(exceptionHandler);
this.dispatchers[i] = dispatcher;
}
for (int i = 0; i < this.workerCount; i++) {
BaseIOReactor dispatcher = this.dispatchers[i];
this.workers[i] = new Worker(dispatcher, eventDispatch);
this.threads[i] = this.threadFactory.newThread(this.workers[i]);
}
}
try {
for (int i = 0; i < this.workerCount; i++) {
if (this.status != IOReactorStatus.ACTIVE) {
return;
}
this.threads[i].start();
}
for (;;) {
int readyCount;
try {
readyCount = this.selector.select(this.selectTimeout);
} catch (InterruptedIOException ex) {
throw ex;
} catch (IOException ex) {
throw new IOReactorException("Unexpected selector failure", ex);
}
if (this.status.compareTo(IOReactorStatus.ACTIVE) > 0) {
break;
}
processEvents(readyCount);
// Verify I/O dispatchers
for (int i = 0; i < this.workerCount; i++) {
Worker worker = this.workers[i];
Thread thread = this.threads[i];
if (!thread.isAlive()) {
Exception ex = worker.getException();
if (ex != null) {
throw new IOReactorException(
"I/O dispatch worker terminated abnormally", ex);
}
}
}
}
} catch (ClosedSelectorException ex) {
addExceptionEvent(ex);
} catch (IOReactorException ex) {
if (ex.getCause() != null) {
addExceptionEvent(ex.getCause());
}
throw ex;
} finally {
doShutdown();
synchronized (this.statusLock) {
this.status = IOReactorStatus.SHUT_DOWN;
this.statusLock.notifyAll();
}
}
}
/**
* Activates the shutdown sequence for this reactor. This method will cancel
* all pending session requests, close out all active I/O channels,
* make an attempt to terminate all worker I/O reactors gracefully,
* and finally force-terminate those I/O reactors that failed to
* terminate after the specified grace period.
* <p>
* The following HTTP parameters affect execution of this method:
* <p>
* The {@link IOReactorConfig#getGracePeriod()} parameter determines the
* grace period the I/O reactors are expected to block waiting
* for individual worker threads to terminate cleanly.
*
* @throws InterruptedIOException if the shutdown sequence has been
* interrupted.
*/
protected void doShutdown() throws InterruptedIOException {
synchronized (this.statusLock) {
if (this.status.compareTo(IOReactorStatus.SHUTTING_DOWN) >= 0) {
return;
}
this.status = IOReactorStatus.SHUTTING_DOWN;
}
try {
cancelRequests();
} catch (IOReactorException ex) {
if (ex.getCause() != null) {
addExceptionEvent(ex.getCause());
}
}
this.selector.wakeup();
// Close out all channels
if (this.selector.isOpen()) {
Set<SelectionKey> keys = this.selector.keys();
for (Iterator<SelectionKey> it = keys.iterator(); it.hasNext(); ) {
try {
SelectionKey key = it.next();
Channel channel = key.channel();
if (channel != null) {
channel.close();
}
} catch (IOException ex) {
addExceptionEvent(ex);
}
}
// Stop dispatching I/O events
try {
this.selector.close();
} catch (IOException ex) {
addExceptionEvent(ex);
}
}
// Attempt to shut down I/O dispatchers gracefully
for (int i = 0; i < this.workerCount; i++) {
BaseIOReactor dispatcher = this.dispatchers[i];
dispatcher.gracefulShutdown();
}
try {
// Force shut down I/O dispatchers if they fail to terminate
// in time
for (int i = 0; i < this.workerCount; i++) {
BaseIOReactor dispatcher = this.dispatchers[i];
if (dispatcher.getStatus() != IOReactorStatus.INACTIVE) {
dispatcher.awaitShutdown(this.gracePeriod);
}
if (dispatcher.getStatus() != IOReactorStatus.SHUT_DOWN) {
try {
dispatcher.hardShutdown();
} catch (IOReactorException ex) {
if (ex.getCause() != null) {
addExceptionEvent(ex.getCause());
}
}
}
}
// Join worker threads
for (int i = 0; i < this.workerCount; i++) {
Thread t = this.threads[i];
if (t != null) {
t.join(this.gracePeriod);
}
}
} catch (InterruptedException ex) {
throw new InterruptedIOException(ex.getMessage());
}
}
/**
* Assigns the given channel entry to one of the worker I/O reactors.
*
* @param entry the channel entry.
*/
protected void addChannel(final ChannelEntry entry) {
// Distribute new channels among the workers
int i = Math.abs(this.currentWorker++ % this.workerCount);
this.dispatchers[i].addChannel(entry);
}
/**
* Registers the given channel with the main {@link Selector}.
*
* @param channel the channel.
* @param ops interest ops.
* @return selection key.
* @throws ClosedChannelException if the channel has been already closed.
*/
protected SelectionKey registerChannel(
final SelectableChannel channel, int ops) throws ClosedChannelException {
return channel.register(this.selector, ops);
}
/**
* Prepares the given {@link Socket} by resetting some of its properties.
*
* @param socket the socket
* @throws IOException in case of an I/O error.
*/
protected void prepareSocket(final Socket socket) throws IOException {
socket.setTcpNoDelay(this.tcpNoDelay);
if (this.soLinger >= 0) {
socket.setSoLinger(this.soLinger > 0, this.soLinger);
}
}
/**
* Blocks for the given period of time in milliseconds awaiting
* the completion of the reactor shutdown. If the value of
* <code>timeout</code> is set to <code>0</code> this method blocks
* indefinitely.
*
* @param timeout the maximum wait time.
* @throws InterruptedException if interrupted.
*/
protected void awaitShutdown(long timeout) throws InterruptedException {
synchronized (this.statusLock) {
long deadline = System.currentTimeMillis() + timeout;
long remaining = timeout;
while (this.status != IOReactorStatus.SHUT_DOWN) {
this.statusLock.wait(remaining);
if (timeout > 0) {
remaining = deadline - System.currentTimeMillis();
if (remaining <= 0) {
break;
}
}
}
}
}
public void shutdown() throws IOException {
shutdown(2000);
}
public void shutdown(long waitMs) throws IOException {
synchronized (this.statusLock) {
if (this.status.compareTo(IOReactorStatus.ACTIVE) > 0) {
return;
}
if (this.status.compareTo(IOReactorStatus.INACTIVE) == 0) {
this.status = IOReactorStatus.SHUT_DOWN;
cancelRequests();
return;
}
this.status = IOReactorStatus.SHUTDOWN_REQUEST;
}
this.selector.wakeup();
try {
awaitShutdown(waitMs);
} catch (InterruptedException ignore) {
}
}
static class Worker implements Runnable {
final BaseIOReactor dispatcher;
final IOEventDispatch eventDispatch;
private volatile Exception exception;
public Worker(final BaseIOReactor dispatcher, final IOEventDispatch eventDispatch) {
super();
this.dispatcher = dispatcher;
this.eventDispatch = eventDispatch;
}
public void run() {
try {
this.dispatcher.execute(this.eventDispatch);
} catch (Exception ex) {
this.exception = ex;
}
}
public Exception getException() {
return this.exception;
}
}
static class DefaultThreadFactory implements ThreadFactory {
private static AtomicInteger COUNT = new AtomicInteger(0);
public Thread newThread(final Runnable r) {
return new Thread(r, "I/O dispatcher " + (COUNT.incrementAndGet()));
}
}
}