content: /**
   * 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;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  public class SelectorWorker implements Runnable {
  
      private static final Logger LOG = LoggerFactory.getLogger(SelectorWorker.class);
  
      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<Runnable>();
  
      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) {
                  LOG.debug(e.getMessage(), e);
              }
          }
      }
  
      @Override
      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<SelectionKey> keys = selector.selectedKeys();
  
                  for (Iterator<SelectionKey> i = keys.iterator(); i.hasNext();) {
                      final SelectionKey key = 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() {
                              @Override
                              public void run() {
                                  try {
                                      s.onSelect();
                                      s.enable();
                                  } catch (Throwable e) {
                                      s.onError(e);
                                  }
                              }
                          });
  
                      } catch (Throwable e) {
                          s.onError(e);
                      }
                  }
              }
          } catch (Throwable e) {
              // Notify all the selections that the error occurred.
              Set<SelectionKey> keys = selector.keys();
              for (Iterator<SelectionKey> i = keys.iterator(); i.hasNext();) {
                  SelectionKey key = i.next();
                  SelectorSelection s = (SelectorSelection) key.attachment();
                  s.onError(e);
              }
          } finally {
              try {
                  manager.onWorkerEmptyEvent(this);
                  selector.close();
              } catch (IOException ignore) {
                  LOG.debug(ignore.getMessage(), ignore);
              }
              Thread.currentThread().setName(origName);
          }
      }
  }
  