ActiveMQ example source code file (SelectorWorker.java)

This example ActiveMQ source code file (SelectorWorker.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - ActiveMQ tags/keywords

atomicinteger, atomicinteger, io, ioexception, iterator, runnable, runnable, selectionkey, selectionkey, selector, selectorselection, selectorworker, set, threading, threads, throwable, throwable, util

The ActiveMQ SelectorWorker.java source code

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF 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.apache.activemq.transport.nio;

import java.io.IOException;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.util.Iterator;
import java.util.Set;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.atomic.AtomicInteger;

public class SelectorWorker implements Runnable {

    private static final AtomicInteger NEXT_ID = new AtomicInteger();

    final SelectorManager manager;
    final Selector selector;
    final int id = NEXT_ID.getAndIncrement();
    private final int maxChannelsPerWorker;

    final AtomicInteger retainCounter = new AtomicInteger(1);
    private final ConcurrentLinkedQueue<Runnable> ioTasks = new ConcurrentLinkedQueue();
       
    public SelectorWorker(SelectorManager manager) throws IOException {
        this.manager = manager;
        selector = Selector.open();
        maxChannelsPerWorker = manager.getMaxChannelsPerWorker();
        manager.getSelectorExecutor().execute(this);
    }

    void retain() {
        if (retainCounter.incrementAndGet() == maxChannelsPerWorker) {
            manager.onWorkerFullEvent(this);
        }
    }

    void release() {
        int use = retainCounter.decrementAndGet();
        if (use == 0) {
            manager.onWorkerEmptyEvent(this);
        } else if (use == maxChannelsPerWorker - 1) {
            manager.onWorkerNotFullEvent(this);
        }
    }
    
    boolean isReleased() {
        return retainCounter.get()==0;
    }


    public void addIoTask(Runnable work) {
        ioTasks.add(work);
        selector.wakeup();
    }
    
    private void processIoTasks() {
        Runnable task; 
        while( (task= ioTasks.poll()) !=null ) {
            try {
                task.run();
            } catch (Throwable e) {
                e.printStackTrace();
            }
        }
    }

    

    public void run() {

        String origName = Thread.currentThread().getName();
        try {
            Thread.currentThread().setName("Selector Worker: " + id);
            while (!isReleased()) {
            	
            	processIoTasks();
            	
            	int count = selector.select(10);
            	
                if (count == 0) {
                    continue;
                }

                // Get a java.util.Set containing the SelectionKey objects
                // for all channels that are ready for I/O.
                Set keys = selector.selectedKeys();

                for (Iterator i = keys.iterator(); i.hasNext();) {
                    final SelectionKey key = (SelectionKey)i.next();
                    i.remove();

                    final SelectorSelection s = (SelectorSelection)key.attachment();
                    try {
                        if( key.isValid() ) {
                            key.interestOps(0);
                        }

                        // Kick off another thread to find newly selected keys
                        // while we process the
                        // currently selected keys
                        manager.getChannelExecutor().execute(new Runnable() {
                            public void run() {
                                try {
                                    s.onSelect();
                                    s.enable();
                                } catch (Throwable e) {
                                    s.onError(e);
                                }
                            }
                        });

                    } catch (Throwable e) {
                        s.onError(e);
                    }

                }

            }
        } catch (Throwable e) {         	
            e.printStackTrace();
            // Notify all the selections that the error occurred.
            Set keys = selector.keys();
            for (Iterator i = keys.iterator(); i.hasNext();) {
                SelectionKey key = (SelectionKey)i.next();
                SelectorSelection s = (SelectorSelection)key.attachment();
                s.onError(e);
            }
        } finally {
            try {
                manager.onWorkerEmptyEvent(this);
                selector.close();
            } catch (IOException ignore) {
            	ignore.printStackTrace();
            }
            Thread.currentThread().setName(origName);
        }
    }

}