com.google.code.yanf4j.util.SelectorFactory Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of xmemcached Show documentation
Extreme performance modern memcached client for java
The newest version!
/*
 * The contents of this file are subject to the terms of the Common Development and Distribution
 * License (the License). You may not use this file except in compliance with the License.
 * 
 * You can obtain a copy of the license at https://glassfish.dev.java.net/public/CDDLv1.0.html or
 * glassfish/bootstrap/legal/CDDLv1.0.txt. See the License for the specific language governing
 * permissions and limitations under the License.
 * 
 * When distributing Covered Code, include this CDDL Header Notice in each file and include the
 * License file at glassfish/bootstrap/legal/CDDLv1.0.txt. If applicable, add the following below
 * the CDDL Header, with the fields enclosed by brackets [] replaced by you own identifying
 * information: "Portions Copyrighted [year] [name of copyright owner]"
 * 
 * Copyright 2007 Sun Microsystems, Inc. All rights reserved.
 */
package com.google.code.yanf4j.util;

import java.io.IOException;
import java.nio.channels.Selector;
import java.util.EmptyStackException;
import java.util.Stack;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Temp selector factory,come from grizzly
 * 
 * @author dennis zhuang
 */
public class SelectorFactory {

  public static final int DEFAULT_MAX_SELECTORS = 20;

  private static final Logger logger = LoggerFactory.getLogger(SelectorFactory.class);
  /**
   * The timeout before we exit.
   */
  public final static long timeout = 5000;

  /**
   * The number of Selector to create.
   */
  private static int maxSelectors;

  /**
   * Cache of Selector
   */
  private final static Stack selectors = new Stack();

  /**
   * Creates the Selector
   */
  static {
    try {
      setMaxSelectors(DEFAULT_MAX_SELECTORS);
    } catch (IOException ex) {
      logger.warn("SelectorFactory initializing Selector pool", ex);
    }
  }

  /**
   * Set max selector pool size.
   * 
   * @param size max pool size
   */
  public final static void setMaxSelectors(int size) throws IOException {
    synchronized (selectors) {
      if (size < maxSelectors) {
        reduce(size);
      } else if (size > maxSelectors) {
        grow(size);
      }

      maxSelectors = size;
    }
  }

  /**
   * Returns max selector pool size
   * 
   * @return max pool size
   */
  public final static int getMaxSelectors() {
    return maxSelectors;
  }

  /**
   * Get a exclusive Selector
   * 
   * @return Selector
   */
  public final static Selector getSelector() {
    synchronized (selectors) {
      Selector s = null;
      try {
        if (selectors.size() != 0) {
          s = selectors.pop();
        }
      } catch (EmptyStackException ex) {
      }

      int attempts = 0;
      try {
        while (s == null && attempts < 2) {
          selectors.wait(timeout);
          try {
            if (selectors.size() != 0) {
              s = selectors.pop();
            }
          } catch (EmptyStackException ex) {
            break;
          }
          attempts++;
        }
      } catch (InterruptedException ex) {
      }
      return s;
    }
  }

  /**
   * Return the Selector to the cache
   * 
   * @param s Selector
   */
  public final static void returnSelector(Selector s) {
    synchronized (selectors) {
      selectors.push(s);
      if (selectors.size() == 1) {
        selectors.notify();
      }
    }
  }

  /**
   * Increase Selector pool size
   */
  private static void grow(int size) throws IOException {
    for (int i = 0; i < size - maxSelectors; i++) {
      selectors.add(Selector.open());
    }
  }

  /**
   * Decrease Selector pool size
   */
  private static void reduce(int size) {
    for (int i = 0; i < maxSelectors - size; i++) {
      try {
        Selector selector = selectors.pop();
        selector.close();
      } catch (IOException e) {
        logger.error("SelectorFactory.reduce", e);
      }
    }
  }

}