Examples of java.nio.channels.SelectableChannel

java.nio.channels.SelectableChannel
A channel that can be multiplexed via a {@link Selector}.
In order to be used with a selector, an instance of this class must first be registered via the {@link #register(Selector,int,Object) register} method. This method returns a new {@link SelectionKey} objectthat represents the channel's registration with the selector.
Once registered with a selector, a channel remains registered until it is deregistered. This involves deallocating whatever resources were allocated to the channel by the selector.
A channel cannot be deregistered directly; instead, the key representing its registration must be cancelled. Cancelling a key requests that the channel be deregistered during the selector's next selection operation. A key may be cancelled explicitly by invoking its {@link SelectionKey#cancel() cancel} method. All of a channel's keys are cancelledimplicitly when the channel is closed, whether by invoking its {@link Channel#close close} method or by interrupting a thread blocked in an I/Ooperation upon the channel.
If the selector itself is closed then the channel will be deregistered, and the key representing its registration will be invalidated, without further delay.
A channel may be registered at most once with any particular selector.
Whether or not a channel is registered with one or more selectors may be determined by invoking the {@link #isRegistered isRegistered} method.
Selectable channels are safe for use by multiple concurrent threads.

Blocking mode
A selectable channel is either in blocking mode or in non-blocking mode. In blocking mode, every I/O operation invoked upon the channel will block until it completes. In non-blocking mode an I/O operation will never block and may transfer fewer bytes than were requested or possibly no bytes at all. The blocking mode of a selectable channel may be determined by invoking its {@link #isBlocking isBlocking} method.
Newly-created selectable channels are always in blocking mode. Non-blocking mode is most useful in conjunction with selector-based multiplexing. A channel must be placed into non-blocking mode before being registered with a selector, and may not be returned to blocking mode until it has been deregistered. @author Mark Reinhold @author JSR-51 Expert Group @version 1.35, 05/11/17 @since 1.4 @see SelectionKey @see Selector

        return new IoSessionIterator(selector.selectedKeys());
    }


    @Override
    protected void init(NioSession session) throws Exception {
        SelectableChannel ch = (SelectableChannel) session.getChannel();
        ch.configureBlocking(false);
        session.setSelectionKey(ch.register(selector, SelectionKey.OP_READ, session));
    }

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                newSelector = selectorProvider.openSelector();
            }


            // Loop on all the registered keys, and register them on the new selector
            for (SelectionKey key : keys) {
                SelectableChannel ch = key.channel();


                // Don't forget to attache the session, and back !
                NioSession session = (NioSession) key.attachment();
                SelectionKey newKey = ch.register(newSelector, key.interestOps(), session);
                session.setSelectionKey(newKey);
            }


            // Now we can close the old selector and switch it
            selector.close();

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            Set<SelectionKey> keys = selector.keys();


            // Loop on all the keys to see if one of them
            // has a closed channel
            for (SelectionKey key : keys) {
                SelectableChannel channel = key.channel();


                if ((((channel instanceof DatagramChannel) && !((DatagramChannel) channel).isConnected()))
                        || ((channel instanceof SocketChannel) && !((SocketChannel) channel).isConnected())) {
                    // The channel is not connected anymore. Cancel
                    // the associated key then.

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    }


    @Override
    public NextAction handleAccept(final FilterChainContext ctx) throws IOException {
        final NIOConnection nioConnection = (NIOConnection) ctx.getConnection();
        final SelectableChannel channel = nioConnection.getChannel();
        if (targetInitializer == null) {
            synchronized (LOCK_OBJ) {
                if (targetInitializer == null) {
                    LazyServiceInitializer targetInitializerLocal = null;
                    for (final ActiveDescriptor<?> initializer : initializerImplList) {
                        String listenerName = listener.getName();
                        String serviceName = initializer.getName();
                        if (serviceName != null && listenerName.equalsIgnoreCase(serviceName)) {
                            targetInitializerLocal = (LazyServiceInitializer) locator.getServiceHandle(initializer).getService();
                            break;
                        }
                    }


                    if (targetInitializerLocal == null) {
                        logger.log(Level.SEVERE, "NO Lazy Initialiser implementation was found for port = {0}",
                                String.valueOf(listener.getPort()));
                        nioConnection.close();


                        return ctx.getStopAction();
                    }
                    if (!targetInitializerLocal.initializeService()) {
                        logger.log(Level.SEVERE, "Lazy Service initialization failed for port = {0}",
                                String.valueOf(listener.getPort()));


                        nioConnection.close();


                        return ctx.getStopAction();
                    }
                    
                    targetInitializer = targetInitializerLocal;
                }
            }
        }


        final NextAction nextAction = ctx.getSuspendAction();
        ctx.completeAndRecycle();


        // Deregister channel
        final SelectorRunner runner = nioConnection.getSelectorRunner();
        final SelectorHandler selectorHandler =
                ((NIOTransport) nioConnection.getTransport()).getSelectorHandler();


        selectorHandler.deregisterChannel(runner, channel);


        // Underlying service rely the channel is blocking
        channel.configureBlocking(true);
        targetInitializer.handleRequest(channel);


        return nextAction;
    }

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                        }
                        else if (o instanceof ChangeSelectableChannel)
                        {
                            // finish accepting/connecting this connection
                            final ChangeSelectableChannel asc = (ChangeSelectableChannel)o;
                            final SelectableChannel channel=asc._channel;
                            final Object att = asc._attachment;


                            if ((channel instanceof SocketChannel) && ((SocketChannel)channel).isConnected())
                            {
                                key = channel.register(selector,SelectionKey.OP_READ,att);
                                SelectChannelEndPoint endpoint = newEndPoint((SocketChannel)channel,this,key);
                                key.attach(endpoint);
                                endpoint.dispatch();
                            }
                            else if (channel.isOpen())
                            {
                                channel.register(selector,SelectionKey.OP_CONNECT,att);
                            }
                        }
                        else if (o instanceof SocketChannel)
                        {
                            final SocketChannel channel=(SocketChannel)o;


                            if (channel.isConnected())
                            {
                                key = channel.register(selector,SelectionKey.OP_READ,null);
                                SelectChannelEndPoint endpoint = newEndPoint(channel,this,key);
                                key.attach(endpoint);
                                endpoint.dispatch();
                            }
                            else if (channel.isOpen())
                            {
                                channel.register(selector,SelectionKey.OP_CONNECT,null);
                            }
                        }
                        else if (o instanceof ServerSocketChannel)
                        {
                            ServerSocketChannel channel = (ServerSocketChannel)o;
                            channel.register(getSelector(),SelectionKey.OP_ACCEPT);
                        }
                        else if (o instanceof ChangeTask)
                        {
                            ((ChangeTask)o).run();
                        }
                        else
                            throw new IllegalArgumentException(o.toString());
                    }
                    catch (Exception e)
                    {
                        if (isRunning())
                            Log.warn(e);
                        else
                            Log.debug(e);
                    }
                }
                changes.clear();


                long idle_next = 0;
                long retry_next = 0;
                long now=System.currentTimeMillis();
                synchronized (this)
                {
                    _idleTimeout.setNow(now);
                    _retryTimeout.setNow(now);
                    if (_lowResourcesConnections>0 && selector.keys().size()>_lowResourcesConnections)
                        _idleTimeout.setDuration(_lowResourcesMaxIdleTime);
                    else 
                        _idleTimeout.setDuration(_maxIdleTime);
                    idle_next=_idleTimeout.getTimeToNext();
                    retry_next=_retryTimeout.getTimeToNext();
                }


                // workout how low to wait in select
                long wait = 1000L;  // not getMaxIdleTime() as the now value of the idle timers needs to be updated.
                if (idle_next >= 0 && wait > idle_next)
                    wait = idle_next;
                if (wait > 0 && retry_next >= 0 && wait > retry_next)
                    wait = retry_next;
    
                // Do the select.
                if (wait > 2) // TODO tune or configure this
                {
                    // If we are in pausing mode
                    if (_pausing)
                    {
                        try
                        {
                            Thread.sleep(__BUSY_PAUSE); // pause to reduce impact of  busy loop
                        }
                        catch(InterruptedException e)
                        {
                            Log.ignore(e);
                        }
                    }
                        
                    long before=now;
                    int selected=selector.select(wait);
                    now = System.currentTimeMillis();
                    _idleTimeout.setNow(now);
                    _retryTimeout.setNow(now);
                    _selects++;


                    // Look for JVM bugs over a monitor period.
                    // http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6403933
                    // http://bugs.sun.com/view_bug.do?bug_id=6693490
                    if (now>_monitorNext)
                    {
                        _selects=(int)(_selects*__MONITOR_PERIOD/(now-_monitorStart));
                        _pausing=_selects>__MAX_SELECTS;
                        if (_pausing)
                            _paused++;
                            
                        _selects=0;
                        _jvmBug=0;
                        _monitorStart=now;
                        _monitorNext=now+__MONITOR_PERIOD;
                    }
                    
                    if (now>_log)
                    {
                        if (_paused>0)  
                            Log.info(this+" Busy selector - injecting delay "+_paused+" times");


                        if (_jvmFix2>0)
                            Log.info(this+" JVM BUG(s) - injecting delay"+_jvmFix2+" times");


                        if (_jvmFix1>0)
                            Log.info(this+" JVM BUG(s) - recreating selector "+_jvmFix1+" times, canceled keys "+_jvmFix0+" times");


                        else if(Log.isDebugEnabled() && _jvmFix0>0)
                            Log.info(this+" JVM BUG(s) - canceled keys "+_jvmFix0+" times");
                        _paused=0;
                        _jvmFix2=0;
                        _jvmFix1=0;
                        _jvmFix0=0;
                        _log=now+60000;
                    }
                    
                    // If we see signature of possible JVM bug, increment count.
                    if (selected==0 && wait>10 && (now-before)<(wait/2))
                    {
                        // Increment bug count and try a work around
                        _jvmBug++;
                        if (_jvmBug>(__JVMBUG_THRESHHOLD))
                        {
                            try
                            {
                                if (_jvmBug==__JVMBUG_THRESHHOLD+1)
                                    _jvmFix2++;
                                    
                                Thread.sleep(__BUSY_PAUSE); // pause to avoid busy loop
                            }
                            catch(InterruptedException e)
                            {
                                Log.ignore(e);
                            }
                        }
                        else if (_jvmBug==__JVMBUG_THRESHHOLD)
                        {
                            synchronized (this)
                            {
                                // BLOODY SUN BUG !!!  Try refreshing the entire selector.
                                _jvmFix1++;
                                
                                final Selector new_selector = Selector.open();
                                Iterator iterator = _selector.keys().iterator();
                                while (iterator.hasNext())
                                {
                                    SelectionKey k = (SelectionKey)iterator.next();
                                    if (!k.isValid() || k.interestOps()==0)
                                        continue;
                                    
                                    final SelectableChannel channel = k.channel();
                                    final Object attachment = k.attachment();
                                    
                                    if (attachment==null)
                                        addChange(channel);
                                    else
                                        addChange(channel,attachment);
                                }
                                _selector.close();
                                _selector=new_selector;
                                return;
                            }
                        }
                        else if (_jvmBug%32==31) // heuristic attempt to cancel key 31,63,95,... loops
                        {
                            // Cancel keys with 0 interested ops
                            int cancelled=0;
                            Iterator iter = selector.keys().iterator();
                            while(iter.hasNext())
                            {
                                SelectionKey k = (SelectionKey) iter.next();
                                if (k.isValid()&&k.interestOps()==0)
                                {
                                    k.cancel();
                                    cancelled++;
                                }
                            }
                            if (cancelled>0)
                                _jvmFix0++;
                            
                            return;
                        }
                    }
                    else if (__BUSY_KEY>0 && selected==1 && _selects>__MAX_SELECTS)
                    {
                        // Look for busy key
                        SelectionKey busy = (SelectionKey)selector.selectedKeys().iterator().next();
                        if (busy==_busyKey)
                        {
                            if (++_busyKeyCount>__BUSY_KEY && !(busy.channel() instanceof ServerSocketChannel))
                            {
                                SelectChannelEndPoint endpoint = (SelectChannelEndPoint)busy.attachment();
                                Log.warn("Busy Key "+busy.channel()+" "+endpoint);
                                busy.cancel();
                                if (endpoint!=null)
                                    endpoint.close();
                            }
                        }
                        else
                            _busyKeyCount=0;
                        _busyKey=busy;
                    }
                }
                else 
                {
                    selector.selectNow();
                    _selects++;
                }


                // have we been destroyed while sleeping
                if (_selector==null || !selector.isOpen())
                    return;


                // Look for things to do
                Iterator iter = selector.selectedKeys().iterator();
                while (iter.hasNext())
                {
                    key = (SelectionKey) iter.next();
                                        
                    try
                    {
                        if (!key.isValid())
                        {
                            key.cancel();
                            SelectChannelEndPoint endpoint = (SelectChannelEndPoint)key.attachment();
                            if (endpoint != null)
                                endpoint.doUpdateKey();
                            continue;
                        }
                        
                        Object att = key.attachment();
                        
                        if (att instanceof SelectChannelEndPoint)
                        {
                            SelectChannelEndPoint endpoint = (SelectChannelEndPoint)att;
                            endpoint.dispatch();
                        }
                        else if (key.isAcceptable())
                        {
                            SocketChannel channel = acceptChannel(key);
                            if (channel==null)
                                continue;


                            channel.configureBlocking(false);


                            // TODO make it reluctant to leave 0
                            _nextSet=++_nextSet%_selectSet.length;


                            // Is this for this selectset
                            if (_nextSet==_setID)
                            {
                                // bind connections to this select set.
                                SelectionKey cKey = channel.register(_selectSet[_nextSet].getSelector(), SelectionKey.OP_READ);
                                SelectChannelEndPoint endpoint=newEndPoint(channel,_selectSet[_nextSet],cKey);
                                cKey.attach(endpoint);
                                if (endpoint != null)
                                    endpoint.dispatch();
                            }
                            else
                            {
                                // nope - give it to another.
                                _selectSet[_nextSet].addChange(channel);
                                _selectSet[_nextSet].wakeup();
                            }
                        }
                        else if (key.isConnectable())
                        {
                            // Complete a connection of a registered channel
                            SocketChannel channel = (SocketChannel)key.channel();
                            boolean connected=false;
                            try
                            {
                                connected=channel.finishConnect();
                            }
                            catch(Exception e)
                            {
                                connectionFailed(channel,e,att);
                            }

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          for (SelectionKey k : selector.keys()) {
            if (!k.isValid() || k.interestOps() == 0) {
              continue;
            }


            final SelectableChannel channel = k.channel();
            final Object attachment = k.attachment();


            channel.register(new_selector, k.interestOps(),
                attachment);
          }


          selector.close();
          selector = new_selector;

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            return true;
        }
        final Ruby runtime = getRuntime();
        RubyThread thread = runtime.getCurrentContext().getThread();


        SelectableChannel selectable = (SelectableChannel)io.getChannel();
        selectable.configureBlocking(false);
        final Selector selector = runtime.getSelectorPool().get();
        final SelectionKey key = selectable.register(selector, operations);


        try {
            io.addBlockingThread(thread);


            final int[] result = new int[1];

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    public int write(ByteBuffer src, boolean blocking) throws SSLException, IOException {
        if(initialHandshake) {
            throw new IOException("Writing not possible during handshake");
        }


        SelectableChannel selectable = getSocketChannel();
        boolean blockingMode = selectable.isBlocking();
        if (!blocking) selectable.configureBlocking(false);


        try {
            if(netData.hasRemaining()) {
                flushData(blocking);
            }
            netData.clear();
            SSLEngineResult res = engine.wrap(src, netData);
            netData.flip();
            flushData(blocking);
            return res.bytesConsumed();
        } finally {
            if (!blocking) selectable.configureBlocking(blockingMode);
        }
    }

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                    if (timeBlocked < minSelectTimeout) {
                        boolean notConnected = false;
                        // loop over all keys as the selector may was unblocked because of a closed channel
                        for (SelectionKey key: selector.keys()) {
                            SelectableChannel ch = key.channel();
                            try {
                                if (ch instanceof DatagramChannel && !ch.isOpen() ||
                                        ch instanceof SocketChannel && !((SocketChannel) ch).isConnected()) {
                                    notConnected = true;
                                    // cancel the key just to be on the safe side
                                    key.cancel();
                                }

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        return new IoSessionIterator(selector.selectedKeys());
    }


    @Override
    protected void init(NioSession session) throws Exception {
        SelectableChannel ch = (SelectableChannel) session.getChannel();
        ch.configureBlocking(false);
        session.setSelectionKey(ch.register(selector, SelectionKey.OP_READ, session));
    }

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Examples of java.nio.channels.SelectableChannel

Blocking mode

Related Classes of java.nio.channels.SelectableChannel