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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 <a href="http://mina.apache.org">Apache MINA Project</a>
32   */
33  public class IoEventQueueThrottle implements IoEventQueueHandler {
34      /** A logger for this class */
35      private final static Logger LOGGER = LoggerFactory.getLogger(IoEventQueueThrottle.class);
36  
37      /** The event size estimator instance */
38      private final IoEventSizeEstimator eventSizeEstimator;
39  
40      private volatile int threshold;
41  
42      private final Object lock = new Object();
43  
44      private final AtomicInteger counter = new AtomicInteger();
45  
46      private int waiters;
47  
48      public IoEventQueueThrottle() {
49          this(new DefaultIoEventSizeEstimator(), 65536);
50      }
51  
52      public IoEventQueueThrottle(int threshold) {
53          this(new DefaultIoEventSizeEstimator(), threshold);
54      }
55  
56      public IoEventQueueThrottle(IoEventSizeEstimator eventSizeEstimator, int threshold) {
57          if (eventSizeEstimator == null) {
58              throw new IllegalArgumentException("eventSizeEstimator");
59          }
60          
61          this.eventSizeEstimator = eventSizeEstimator;
62  
63          setThreshold(threshold);
64      }
65  
66      public IoEventSizeEstimator getEventSizeEstimator() {
67          return eventSizeEstimator;
68      }
69  
70      public int getThreshold() {
71          return threshold;
72      }
73  
74      public int getCounter() {
75          return counter.get();
76      }
77  
78      public void setThreshold(int threshold) {
79          if (threshold <= 0) {
80              throw new IllegalArgumentException("threshold: " + threshold);
81          }
82          
83          this.threshold = threshold;
84      }
85  
86      public boolean accept(Object source, IoEvent event) {
87          return true;
88      }
89  
90      public void offered(Object source, IoEvent event) {
91          int eventSize = estimateSize(event);
92          int currentCounter = counter.addAndGet(eventSize);
93          logState();
94  
95          if (currentCounter >= threshold) {
96              block();
97          }
98      }
99  
100     public void polled(Object source, IoEvent event) {
101         int eventSize = estimateSize(event);
102         int currentCounter = counter.addAndGet(-eventSize);
103 
104         logState();
105 
106         if (currentCounter < threshold) {
107             unblock();
108         }
109     }
110 
111     private int estimateSize(IoEvent event) {
112         int size = getEventSizeEstimator().estimateSize(event);
113         
114         if (size < 0) {
115             throw new IllegalStateException(IoEventSizeEstimator.class.getSimpleName() + " returned "
116                     + "a negative value (" + size + "): " + event);
117         }
118         
119         return size;
120     }
121 
122     private void logState() {
123         if (LOGGER.isDebugEnabled()) {
124             LOGGER.debug(Thread.currentThread().getName() + " state: " + counter.get() + " / " + getThreshold());
125         }
126     }
127 
128     protected void block() {
129         if (LOGGER.isDebugEnabled()) {
130             LOGGER.debug(Thread.currentThread().getName() + " blocked: " + counter.get() + " >= " + threshold);
131         }
132 
133         synchronized (lock) {
134             while (counter.get() >= threshold) {
135                 waiters++;
136                 try {
137                     lock.wait();
138                 } catch (InterruptedException e) {
139                     // Wait uninterruptably.
140                 } finally {
141                     waiters--;
142                 }
143             }
144         }
145 
146         if (LOGGER.isDebugEnabled()) {
147             LOGGER.debug(Thread.currentThread().getName() + " unblocked: " + counter.get() + " < " + threshold);
148         }
149     }
150 
151     protected void unblock() {
152         synchronized (lock) {
153             if (waiters > 0) {
154                 lock.notifyAll();
155             }
156         }
157     }
158 }