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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          this.eventSizeEstimator = eventSizeEstimator;
61  
62          setThreshold(threshold);
63      }
64  
65      public IoEventSizeEstimator getEventSizeEstimator() {
66          return eventSizeEstimator;
67      }
68  
69      public int getThreshold() {
70          return threshold;
71      }
72  
73      public int getCounter() {
74          return counter.get();
75      }
76  
77      public void setThreshold(int threshold) {
78          if (threshold <= 0) {
79              throw new IllegalArgumentException("threshold: " + threshold);
80          }
81          this.threshold = threshold;
82      }
83  
84      public boolean accept(Object source, IoEvent event) {
85          return true;
86      }
87  
88      public void offered(Object source, IoEvent event) {
89          int eventSize = estimateSize(event);
90          int currentCounter = counter.addAndGet(eventSize);
91          logState();
92  
93          if (currentCounter >= threshold) {
94              block();
95          }
96      }
97  
98      public void polled(Object source, IoEvent event) {
99          int eventSize = estimateSize(event);
100         int currentCounter = counter.addAndGet(-eventSize);
101 
102         logState();
103 
104         if (currentCounter < threshold) {
105             unblock();
106         }
107     }
108 
109     private int estimateSize(IoEvent event) {
110         int size = getEventSizeEstimator().estimateSize(event);
111         if (size < 0) {
112             throw new IllegalStateException(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 }