ConnectedStateMachines.java

/**
 * Copyright (c) 2002-2012 "Neo Technology,"
 * Network Engine for Objects in Lund AB [http://neotechnology.com]
 *
 * This file is part of Neo4j.
 *
 * Neo4j is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */

package org.neo4j.cluster;

import static org.neo4j.cluster.com.message.Message.CONVERSATION_ID;
import static org.neo4j.cluster.com.message.Message.CREATED_BY;

import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Queue;

import org.neo4j.cluster.com.message.Message;
import org.neo4j.cluster.com.message.MessageProcessor;
import org.neo4j.cluster.com.message.MessageSource;
import org.neo4j.cluster.com.message.MessageType;
import org.neo4j.cluster.statemachine.StateMachine;
import org.neo4j.cluster.statemachine.StateTransitionListener;
import org.neo4j.cluster.timeout.TimeoutStrategy;
import org.neo4j.cluster.timeout.Timeouts;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Combines a set of state machines into one. This will
 * typically receive messages from the network and then delegate
 * to the correct state machine based on what type of message comes in.
 * Only one message at a time can be processed.
 */
public class ConnectedStateMachines
        implements MessageProcessor, MessageSource
{
    private final Logger logger = LoggerFactory.getLogger( ConnectedStateMachines.class );

    private final MessageProcessor sender;
    private DelayedDirectExecutor executor;
    private Timeouts timeouts;
    private final Map<Class<? extends MessageType>, StateMachine> stateMachines = new LinkedHashMap<Class<? extends
            MessageType>, StateMachine>();

    private final List<MessageProcessor> outgoingProcessors = new ArrayList<MessageProcessor>();
    private final OutgoingMessageProcessor outgoing;

    public ConnectedStateMachines( MessageSource source,
                                   final MessageProcessor sender,
                                   TimeoutStrategy timeoutStrategy,
                                   DelayedDirectExecutor executor )
    {
        this.sender = sender;
        this.executor = executor;
        this.timeouts = new Timeouts( this, timeoutStrategy );

        outgoing = new OutgoingMessageProcessor();
        source.addMessageProcessor( this );
    }

    public Timeouts getTimeouts()
    {
        return timeouts;
    }

    public synchronized void addStateMachine( StateMachine stateMachine )
    {
        stateMachines.put( stateMachine.getMessageType(), stateMachine );
    }

    public synchronized void removeStateMachine( StateMachine stateMachine )
    {
        stateMachines.remove( stateMachine.getMessageType() );
    }

    public Iterable<StateMachine> getStateMachines()
    {
        return stateMachines.values();
    }

    @Override
    public void addMessageProcessor( MessageProcessor messageProcessor )
    {
        outgoingProcessors.add( messageProcessor );
    }

    public OutgoingMessageProcessor getOutgoing()
    {
        return outgoing;
    }

    @Override
    public synchronized void process( Message<? extends MessageType> message )
    {
        // Lock timeouts while we are processing the message
        synchronized ( timeouts )
        {
            StateMachine stateMachine = stateMachines.get( message.getMessageType().getClass() );
            if ( stateMachine == null )
            {
                return; // No StateMachine registered for this MessageType type - Ignore this
            }

            stateMachine.handle( message, outgoing );

            // Process and send messages
            // Allow state machines to send messages to each other as well in this loop
            Message<? extends MessageType> outgoingMessage;
            try
            {
                while ( (outgoingMessage = outgoing.nextOutgoingMessage()) != null )
                {
                    message.copyHeadersTo( outgoingMessage, CONVERSATION_ID, CREATED_BY );

                    for ( MessageProcessor outgoingProcessor : outgoingProcessors )
                    {
                        try
                        {
                            outgoingProcessor.process( outgoingMessage );
                        }
                        catch ( Throwable e )
                        {
                            logger.warn( "Outgoing message processor threw exception", e );
                        }
                    }

                    if ( outgoingMessage.hasHeader( Message.TO ) )
                    {
                        try
                        {
                            sender.process( outgoingMessage );
                        }
                        catch ( Throwable e )
                        {
                            logger.warn( "Message sending threw exception", e );
                        }
                    }
                    else
                    {
                        // Deliver internally if possible
                        StateMachine internalStatemachine = stateMachines.get( outgoingMessage.getMessageType()
                                .getClass() );
                        //                if (internalStatemachine != null && stateMachine != internalStatemachine )
                        if ( internalStatemachine != null )
                        {
                            internalStatemachine.handle( (Message) outgoingMessage, outgoing );
                        }
                    }
                }
            }
            catch ( Exception e )
            {
                logger.warn( "Error processing message " + message, e );
            }
        }

        // Before returning, process delayed executions so that they are done before returning
        // This will effectively trigger all notifications created by contexts
        executor.drain();
    }

    public void addStateTransitionListener( StateTransitionListener stateTransitionListener )
    {
        for ( StateMachine stateMachine : stateMachines.values() )
        {
            stateMachine.addStateTransitionListener( stateTransitionListener );
        }
    }

    public void removeStateTransitionListener( StateTransitionListener stateTransitionListener )
    {
        for ( StateMachine stateMachine : stateMachines.values() )
        {
            stateMachine.removeStateTransitionListener( stateTransitionListener );
        }
    }

    @Override
    public String toString()
    {
        List<String> states = new ArrayList<String>();
        for ( StateMachine stateMachine : stateMachines.values() )
        {
            states.add( stateMachine.getState().getClass().getSuperclass().getSimpleName() + ":" + stateMachine
                    .getState().toString() );
        }
        return states.toString();
    }

    public StateMachine getStateMachine( Class<? extends MessageType> messageType )
    {
        return stateMachines.get( messageType );
    }

    private class OutgoingMessageProcessor
            implements MessageProcessor
    {
        private Queue<Message<? extends MessageType>> outgoingMessages = new LinkedList<Message<? extends
                MessageType>>();

        @Override
        public synchronized void process( Message<? extends MessageType> message )
        {
            outgoingMessages.offer( message );
        }

        public synchronized Message<? extends MessageType> nextOutgoingMessage()
        {
            return outgoingMessages.poll();
        }
    }
}