View Javadoc

1   /*
2    *  Licensed to the Apache Software Foundation (ASF) under one
3    *  or more contributor license agreements.  See the NOTICE file
4    *  distributed with this work for additional information
5    *  regarding copyright ownership.  The ASF licenses this file
6    *  to you under the Apache License, Version 2.0 (the
7    *  "License"); you may not use this file except in compliance
8    *  with the License.  You may obtain a copy of the License at
9    *
10   *    http://www.apache.org/licenses/LICENSE-2.0
11   *
12   *  Unless required by applicable law or agreed to in writing,
13   *  software distributed under the License is distributed on an
14   *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15   *  KIND, either express or implied.  See the License for the
16   *  specific language governing permissions and limitations
17   *  under the License.
18   *
19   */
20  package org.apache.mina.filter.executor;
21  
22  import java.util.concurrent.atomic.AtomicInteger;
23  
24  import org.apache.mina.core.session.IoEvent;
25  import org.slf4j.Logger;
26  import org.slf4j.LoggerFactory;
27  
28  /**
29   * Throttles incoming or outgoing events.
30   *
31   * @author The Apache MINA Project (dev@mina.apache.org)
32   * @version $Rev: 762170 $, $Date: 2009-04-06 00:01:18 +0200 (Mon, 06 Apr 2009) $
33   */
34  public class IoEventQueueThrottle implements IoEventQueueHandler {
35      /** A logger for this class */
36      private final Logger logger = LoggerFactory.getLogger(getClass());
37  
38      /** The event size estimator instance */
39      private final IoEventSizeEstimator eventSizeEstimator;
40      
41      private volatile int threshold;
42  
43      private final Object lock = new Object();
44      private final AtomicInteger counter = new AtomicInteger();
45      private int waiters;
46  
47      public IoEventQueueThrottle() {
48          this(new DefaultIoEventSizeEstimator(), 65536);
49      }
50  
51      public IoEventQueueThrottle(int threshold) {
52          this(new DefaultIoEventSizeEstimator(), threshold);
53      }
54  
55      public IoEventQueueThrottle(IoEventSizeEstimator eventSizeEstimator, int threshold) {
56          if (eventSizeEstimator == null) {
57              throw new NullPointerException("eventSizeEstimator");
58          }
59          this.eventSizeEstimator = eventSizeEstimator;
60  
61          setThreshold(threshold);
62      }
63  
64      public IoEventSizeEstimator getEventSizeEstimator() {
65          return eventSizeEstimator;
66      }
67  
68      public int getThreshold() {
69          return threshold;
70      }
71  
72      public int getCounter() {
73          return counter.get();
74      }
75  
76      public void setThreshold(int threshold) {
77          if (threshold <= 0) {
78              throw new IllegalArgumentException("threshold: " + threshold);
79          }
80          this.threshold = threshold;
81      }
82  
83      public boolean accept(Object source, IoEvent event) {
84          return true;
85      }
86  
87      public void offered(Object source, IoEvent event) {
88          int eventSize = estimateSize(event);
89          int currentCounter = counter.addAndGet(eventSize);
90          logState();
91  
92          if (currentCounter >= threshold) {
93              block();
94          }
95      }
96  
97      public void polled(Object source, IoEvent event) {
98          int eventSize = estimateSize(event);
99          int currentCounter = counter.addAndGet(-eventSize);
100 
101         logState();
102 
103         if (currentCounter < threshold) {
104             unblock();
105         }
106     }
107 
108     private int estimateSize(IoEvent event) {
109         int size = getEventSizeEstimator().estimateSize(event);
110         if (size < 0) {
111             throw new IllegalStateException(
112                     IoEventSizeEstimator.class.getSimpleName() + " returned " +
113                     "a negative value (" + size + "): " + event);
114         }
115         return size;
116     }
117 
118     private void logState() {
119         if (logger.isDebugEnabled()) {
120             logger.debug(Thread.currentThread().getName() + " state: " + counter.get() + " / " + getThreshold());
121         }
122     }
123 
124     protected void block() {
125         if (logger.isDebugEnabled()) {
126             logger.debug(Thread.currentThread().getName() + " blocked: " + counter.get() + " >= " + threshold);
127         }
128 
129         synchronized (lock) {
130             while (counter.get() >= threshold) {
131                 waiters ++;
132                 try {
133                     lock.wait();
134                 } catch (InterruptedException e) {
135                     // Wait uninterruptably.
136                 } finally {
137                     waiters --;
138                 }
139             }
140         }
141 
142         if (logger.isDebugEnabled()) {
143             logger.debug(Thread.currentThread().getName() + " unblocked: " + counter.get() + " < " + threshold);
144         }
145     }
146 
147     protected void unblock() {
148         synchronized (lock) {
149             if (waiters > 0) {
150                 lock.notify();
151             }
152         }
153     }
154 }