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//
// ========================================================================
// Copyright (c) 1995-2014 Mort Bay Consulting Pty. Ltd.
// ------------------------------------------------------------------------
// All rights reserved. This program and the accompanying materials
// are made available under the terms of the Eclipse Public License v1.0
// and Apache License v2.0 which accompanies this distribution.
//
// The Eclipse Public License is available at
// http://www.eclipse.org/legal/epl-v10.html
//
// The Apache License v2.0 is available at
// http://www.opensource.org/licenses/apache2.0.php
//
// You may elect to redistribute this code under either of these licenses.
// ========================================================================
//
package org.eclipse.jetty.io;
import java.nio.channels.CancelledKeyException;
import java.nio.channels.SelectionKey;
import java.nio.channels.SocketChannel;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicReference;
import org.eclipse.jetty.io.SelectorManager.ManagedSelector;
import org.eclipse.jetty.util.log.Log;
import org.eclipse.jetty.util.log.Logger;
import org.eclipse.jetty.util.thread.Scheduler;
/**
* An ChannelEndpoint that can be scheduled by {@link SelectorManager}.
*/
public class SelectChannelEndPoint extends ChannelEndPoint implements SelectorManager.SelectableEndPoint
{
public static final Logger LOG = Log.getLogger(SelectChannelEndPoint.class);
private final Runnable _updateTask = new Runnable()
{
@Override
public void run()
{
try
{
setKeyInterests();
}
catch (CancelledKeyException x)
{
LOG.debug("Ignoring key update for concurrently closed channel {}", this);
close();
}
catch (Throwable x)
{
LOG.warn("Ignoring key update for " + this, x);
close();
}
}
};
private final AtomicReference _interestState = new AtomicReference<>(State.SELECTING);
/**
* true if {@link ManagedSelector#destroyEndPoint(EndPoint)} has not been called
*/
private final AtomicBoolean _open = new AtomicBoolean();
private final SelectorManager.ManagedSelector _selector;
private final SelectionKey _key;
/**
* The desired value for {@link SelectionKey#interestOps()}
*/
private int _interestOps;
public SelectChannelEndPoint(SocketChannel channel, ManagedSelector selector, SelectionKey key, Scheduler scheduler, long idleTimeout)
{
super(scheduler, channel);
_selector = selector;
_key = key;
setIdleTimeout(idleTimeout);
}
@Override
protected boolean needsFill()
{
changeInterests(SelectionKey.OP_READ, true);
return false;
}
@Override
protected void onIncompleteFlush()
{
changeInterests(SelectionKey.OP_WRITE, true);
}
@Override
public void onSelected()
{
/**
* This method never runs concurrently with other
* methods that update _interestState.
*/
assert _selector.isSelectorThread();
// Remove the readyOps, that here can only be OP_READ or OP_WRITE (or both).
int readyOps = _key.readyOps();
int oldInterestOps = _interestOps;
int newInterestOps = oldInterestOps & ~readyOps;
_interestOps = newInterestOps;
if (!_interestState.compareAndSet(State.SELECTING, State.PENDING))
throw new IllegalStateException("Invalid state: " + _interestState);
if (LOG.isDebugEnabled())
LOG.debug("onSelected {}->{} for {}", oldInterestOps, newInterestOps, this);
if ((readyOps & SelectionKey.OP_READ) != 0)
getFillInterest().fillable();
if ((readyOps & SelectionKey.OP_WRITE) != 0)
getWriteFlusher().completeWrite();
}
@Override
public void updateKey()
{
/**
* This method may run concurrently with {@link #changeInterests(int, boolean)}.
*/
assert _selector.isSelectorThread();
while (true)
{
State current = _interestState.get();
switch (current)
{
case SELECTING:
{
// When a whole cycle triggered by changeInterests()
// happens, we finish the job by updating the key.
setKeyInterests();
return;
}
case PENDING:
{
if (!_interestState.compareAndSet(current, State.UPDATING))
continue;
break;
}
case UPDATING:
{
// Set the key interest as expected.
setKeyInterests();
if (!_interestState.compareAndSet(current, State.SELECTING))
throw new IllegalStateException();
return;
}
case CHANGING:
{
// We lost the race to update _interestOps,
// let changeInterests() perform the update.
return;
}
default:
{
throw new IllegalStateException();
}
}
}
}
private void changeInterests(int operation, boolean add)
{
/**
* This method may run concurrently with {@link #updateKey()}.
*/
boolean pending = false;
while (true)
{
State current = _interestState.get();
switch (current)
{
case SELECTING:
case PENDING:
{
if (!_interestState.compareAndSet(current, State.CHANGING))
continue;
pending = current == State.PENDING;
break;
}
case UPDATING:
{
// We lost the race to update _interestOps, but we
// must update it nonetheless, so yield and spin,
// waiting for the state to be SELECTING again.
Thread.yield();
break;
}
case CHANGING:
{
int oldInterestOps = _interestOps;
int newInterestOps;
if (add)
newInterestOps = oldInterestOps | operation;
else
newInterestOps = oldInterestOps & ~operation;
if (LOG.isDebugEnabled())
LOG.debug("changeInterests pending={} {}->{} for {}", pending, oldInterestOps, newInterestOps, this);
if (newInterestOps != oldInterestOps)
_interestOps = newInterestOps;
if (!_interestState.compareAndSet(current, State.SELECTING))
throw new IllegalStateException("Invalid state: " + current);
// We only update the key if updateKey() does not do it for us,
// because doing it from the selector thread is less expensive.
// This must be done after CASing the state above, otherwise the
// selector may select and call onSelected() concurrently.
submitKeyUpdate(!pending);
return;
}
default:
{
throw new IllegalStateException();
}
}
}
}
protected void submitKeyUpdate(boolean submit)
{
if (submit)
_selector.updateKey(_updateTask);
}
private void setKeyInterests()
{
int oldInterestOps = _key.interestOps();
int newInterestOps = _interestOps;
if (LOG.isDebugEnabled())
LOG.debug("Key interests update {} -> {}", oldInterestOps, newInterestOps);
if (oldInterestOps != newInterestOps)
_key.interestOps(newInterestOps);
}
@Override
public void close()
{
if (_open.compareAndSet(true, false))
{
super.close();
_selector.destroyEndPoint(this);
}
}
@Override
public boolean isOpen()
{
// We cannot rely on super.isOpen(), because there is a race between calls to close() and isOpen():
// a thread may call close(), which flips the boolean but has not yet called super.close(), and
// another thread calls isOpen() which would return true - wrong - if based on super.isOpen().
return _open.get();
}
@Override
public void onOpen()
{
if (_open.compareAndSet(false, true))
super.onOpen();
}
@Override
public String toString()
{
// Do NOT use synchronized (this)
// because it's very easy to deadlock when debugging is enabled.
// We do a best effort to print the right toString() and that's it.
try
{
boolean valid = _key!=null && _key.isValid();
int keyInterests = valid ? _key.interestOps() : -1;
int keyReadiness = valid ? _key.readyOps() : -1;
return String.format("%s{io=%d,kio=%d,kro=%d}",
super.toString(),
_interestOps,
keyInterests,
keyReadiness);
}
catch (CancelledKeyException x)
{
return String.format("%s{io=%s,kio=-2,kro=-2}", super.toString(), _interestOps);
}
}
private enum State
{
SELECTING, PENDING, UPDATING, CHANGING
}
}
