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1   /*
2    * Copyright 2012 The Netty Project
3    *
4    * The Netty Project licenses this file to you under the Apache License,
5    * version 2.0 (the "License"); you may not use this file except in compliance
6    * with the License. You may obtain a copy of the License at:
7    *
8    *   http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13   * License for the specific language governing permissions and limitations
14   * under the License.
15   */
16  package org.jboss.netty.handler.stream;
17  
18  import static org.jboss.netty.channel.Channels.*;
19  
20  import java.io.IOException;
21  import java.nio.channels.ClosedChannelException;
22  import java.util.Queue;
23  import java.util.concurrent.ConcurrentLinkedQueue;
24  import java.util.concurrent.atomic.AtomicBoolean;
25  
26  import org.jboss.netty.buffer.ChannelBuffers;
27  import org.jboss.netty.channel.Channel;
28  import org.jboss.netty.channel.ChannelDownstreamHandler;
29  import org.jboss.netty.channel.ChannelEvent;
30  import org.jboss.netty.channel.ChannelFuture;
31  import org.jboss.netty.channel.ChannelFutureListener;
32  import org.jboss.netty.channel.ChannelHandler;
33  import org.jboss.netty.channel.ChannelHandlerContext;
34  import org.jboss.netty.channel.ChannelPipeline;
35  import org.jboss.netty.channel.ChannelStateEvent;
36  import org.jboss.netty.channel.ChannelUpstreamHandler;
37  import org.jboss.netty.channel.Channels;
38  import org.jboss.netty.channel.LifeCycleAwareChannelHandler;
39  import org.jboss.netty.channel.MessageEvent;
40  import org.jboss.netty.logging.InternalLogger;
41  import org.jboss.netty.logging.InternalLoggerFactory;
42  
43  /**
44   * A {@link ChannelHandler} that adds support for writing a large data stream
45   * asynchronously neither spending a lot of memory nor getting
46   * {@link java.lang.OutOfMemoryError}.  Large data streaming such as file
47   * transfer requires complicated state management in a {@link ChannelHandler}
48   * implementation.  {@link ChunkedWriteHandler} manages such complicated states
49   * so that you can send a large data stream without difficulties.
50   * <p>
51   * To use {@link ChunkedWriteHandler} in your application, you have to insert
52   * a new {@link ChunkedWriteHandler} instance:
53   * <pre>
54   * {@link ChannelPipeline} p = ...;
55   * p.addLast("streamer", <b>new {@link ChunkedWriteHandler}()</b>);
56   * p.addLast("handler", new MyHandler());
57   * </pre>
58   * Once inserted, you can write a {@link ChunkedInput} so that the
59   * {@link ChunkedWriteHandler} can pick it up and fetch the content of the
60   * stream chunk by chunk and write the fetched chunk downstream:
61   * <pre>
62   * {@link Channel} ch = ...;
63   * ch.write(new {@link ChunkedFile}(new File("video.mkv"));
64   * </pre>
65   *
66   * <h3>Sending a stream which generates a chunk intermittently</h3>
67   *
68   * Some {@link ChunkedInput} generates a chunk on a certain event or timing.
69   * Such {@link ChunkedInput} implementation often returns {@code null} on
70   * {@link ChunkedInput#nextChunk()}, resulting in the indefinitely suspended
71   * transfer.  To resume the transfer when a new chunk is available, you have to
72   * call {@link #resumeTransfer()}.
73   * @apiviz.landmark
74   * @apiviz.has org.jboss.netty.handler.stream.ChunkedInput oneway - - reads from
75   */
76  public class ChunkedWriteHandler
77          implements ChannelUpstreamHandler, ChannelDownstreamHandler, LifeCycleAwareChannelHandler {
78  
79      private static final InternalLogger logger =
80          InternalLoggerFactory.getInstance(ChunkedWriteHandler.class);
81  
82      private final Queue<MessageEvent> queue = new ConcurrentLinkedQueue<MessageEvent>();
83  
84      private volatile ChannelHandlerContext ctx;
85      private final AtomicBoolean flush = new AtomicBoolean(false);
86      private MessageEvent currentEvent;
87  
88      /**
89       * Continues to fetch the chunks from the input.
90       */
91      public void resumeTransfer() {
92          ChannelHandlerContext ctx = this.ctx;
93          if (ctx == null) {
94              return;
95          }
96  
97          try {
98              flush(ctx, false);
99          } catch (Exception e) {
100             if (logger.isWarnEnabled()) {
101                 logger.warn("Unexpected exception while sending chunks.", e);
102             }
103         }
104     }
105 
106     public void handleDownstream(ChannelHandlerContext ctx, ChannelEvent e)
107             throws Exception {
108         if (!(e instanceof MessageEvent)) {
109             ctx.sendDownstream(e);
110             return;
111         }
112 
113         boolean offered = queue.offer((MessageEvent) e);
114         assert offered;
115 
116         final Channel channel = ctx.getChannel();
117         // call flush if the channel is writable or not connected. flush(..) will take care of the rest
118 
119         if (channel.isWritable() || !channel.isConnected()) {
120             this.ctx = ctx;
121             flush(ctx, false);
122         }
123     }
124 
125     public void handleUpstream(ChannelHandlerContext ctx, ChannelEvent e)
126             throws Exception {
127         if (e instanceof ChannelStateEvent) {
128             ChannelStateEvent cse = (ChannelStateEvent) e;
129             switch (cse.getState()) {
130             case INTEREST_OPS:
131                 // Continue writing when the channel becomes writable.
132                 flush(ctx, true);
133                 break;
134             case OPEN:
135                 if (!Boolean.TRUE.equals(cse.getValue())) {
136                     // Fail all pending writes
137                     flush(ctx, true);
138                 }
139                 break;
140             }
141         }
142         ctx.sendUpstream(e);
143     }
144 
145     private void discard(ChannelHandlerContext ctx, boolean fireNow) {
146         ClosedChannelException cause = null;
147 
148         for (;;) {
149             MessageEvent currentEvent = this.currentEvent;
150 
151             if (this.currentEvent == null) {
152                 currentEvent = queue.poll();
153             } else {
154                 this.currentEvent = null;
155             }
156 
157             if (currentEvent == null) {
158                 break;
159             }
160 
161 
162             Object m = currentEvent.getMessage();
163             if (m instanceof ChunkedInput) {
164                 closeInput((ChunkedInput) m);
165             }
166 
167             // Trigger a ClosedChannelException
168             if (cause == null) {
169                 cause = new ClosedChannelException();
170             }
171             currentEvent.getFuture().setFailure(cause);
172 
173             currentEvent = null;
174         }
175 
176 
177         if (cause != null) {
178             if (fireNow) {
179                 Channels.fireExceptionCaught(ctx.getChannel(), cause);
180             } else {
181                 Channels.fireExceptionCaughtLater(ctx.getChannel(), cause);
182             }
183         }
184     }
185 
186     private void flush(ChannelHandlerContext ctx, boolean fireNow) throws Exception {
187         boolean acquired = false;
188         final Channel channel = ctx.getChannel();
189 
190         // use CAS to see if the have flush already running, if so we don't need to take futher actions
191         if (acquired = flush.compareAndSet(false, true)) {
192             try {
193 
194                 if (!channel.isConnected()) {
195                     discard(ctx, fireNow);
196                     return;
197                 }
198 
199                 while (channel.isWritable()) {
200                     if (currentEvent == null) {
201                         currentEvent = queue.poll();
202                     }
203 
204                     if (currentEvent == null) {
205                         break;
206                     }
207 
208                     if (currentEvent.getFuture().isDone()) {
209                         // Skip the current request because the previous partial write
210                         // attempt for the current request has been failed.
211                         currentEvent = null;
212                     } else {
213                         final MessageEvent currentEvent = this.currentEvent;
214                         Object m = currentEvent.getMessage();
215                         if (m instanceof ChunkedInput) {
216                             final ChunkedInput chunks = (ChunkedInput) m;
217                             Object chunk;
218                             boolean endOfInput;
219                             boolean suspend;
220                             try {
221                                 chunk = chunks.nextChunk();
222                                 endOfInput = chunks.isEndOfInput();
223                                 if (chunk == null) {
224                                     chunk = ChannelBuffers.EMPTY_BUFFER;
225                                     // No need to suspend when reached at the end.
226                                     suspend = !endOfInput;
227                                 } else {
228                                     suspend = false;
229                                 }
230                             } catch (Throwable t) {
231                                 this.currentEvent = null;
232 
233                                 currentEvent.getFuture().setFailure(t);
234                                 if (fireNow) {
235                                     fireExceptionCaught(ctx, t);
236                                 } else {
237                                     fireExceptionCaughtLater(ctx, t);
238                                 }
239 
240                                 closeInput(chunks);
241                                 break;
242                             }
243 
244                             if (suspend) {
245                                 // ChunkedInput.nextChunk() returned null and it has
246                                 // not reached at the end of input.  Let's wait until
247                                 // more chunks arrive.  Nothing to write or notify.
248                                 break;
249                             } else {
250                                 ChannelFuture writeFuture;
251                                 if (endOfInput) {
252                                     this.currentEvent = null;
253                                     writeFuture = currentEvent.getFuture();
254 
255                                     // Register a listener which will close the input once the write
256                                     // is complete. This is needed because the Chunk may have some
257                                     // resource bound that can not be closed before its not written
258                                     //
259                                     // See https://github.com/netty/netty/issues/303
260                                     writeFuture.addListener(new ChannelFutureListener() {
261 
262                                         public void operationComplete(ChannelFuture future) throws Exception {
263                                             closeInput(chunks);
264                                         }
265                                     });
266                                 } else {
267                                     writeFuture = future(channel);
268                                     writeFuture.addListener(new ChannelFutureListener() {
269                                         public void operationComplete(ChannelFuture future) throws Exception {
270                                             if (!future.isSuccess()) {
271                                                 currentEvent.getFuture().setFailure(future.getCause());
272                                                 closeInput((ChunkedInput) currentEvent.getMessage());
273                                             }
274                                         }
275                                     });
276                                 }
277 
278                                 Channels.write(
279                                         ctx, writeFuture, chunk,
280                                         currentEvent.getRemoteAddress());
281                             }
282                         } else {
283                             this.currentEvent = null;
284                             ctx.sendDownstream(currentEvent);
285                         }
286                     }
287 
288                     if (!channel.isConnected()) {
289                         discard(ctx, fireNow);
290                         return;
291                     }
292                 }
293             } finally {
294                 // mark the flush as done
295                 flush.set(false);
296             }
297 
298         }
299 
300         if (acquired && (!channel.isConnected() || channel.isWritable() && !queue.isEmpty())) {
301             flush(ctx, fireNow);
302         }
303     }
304 
305     static void closeInput(ChunkedInput chunks) {
306         try {
307             chunks.close();
308         } catch (Throwable t) {
309             if (logger.isWarnEnabled()) {
310                 logger.warn("Failed to close a chunked input.", t);
311             }
312         }
313     }
314 
315     public void beforeAdd(ChannelHandlerContext ctx) throws Exception {
316         // nothing to do
317 
318     }
319 
320     public void afterAdd(ChannelHandlerContext ctx) throws Exception {
321         // nothing to do
322 
323     }
324 
325     public void beforeRemove(ChannelHandlerContext ctx) throws Exception {
326         // try to flush again a last time.
327         //
328         // See #304
329         flush(ctx, false);
330     }
331 
332     // This method should not need any synchronization as the ChunkedWriteHandler will not receive any new events
333     public void afterRemove(ChannelHandlerContext ctx) throws Exception {
334         // Fail all MessageEvent's that are left. This is needed because otherwise we would never notify the
335         // ChannelFuture and the registered FutureListener. See #304
336         //
337         Throwable cause = null;
338         boolean fireExceptionCaught = false;
339 
340         for (;;) {
341             MessageEvent currentEvent = this.currentEvent;
342 
343             if (this.currentEvent == null) {
344                 currentEvent = queue.poll();
345             } else {
346                 this.currentEvent = null;
347             }
348 
349             if (currentEvent == null) {
350                 break;
351             }
352 
353             Object m = currentEvent.getMessage();
354             if (m instanceof ChunkedInput) {
355                 closeInput((ChunkedInput) m);
356             }
357 
358             // Create exception
359             if (cause == null) {
360                 cause = new IOException("Unable to flush event, discarding");
361             }
362             currentEvent.getFuture().setFailure(cause);
363             fireExceptionCaught = true;
364 
365             currentEvent = null;
366         }
367 
368         if (fireExceptionCaught) {
369             Channels.fireExceptionCaughtLater(ctx.getChannel(), cause);
370         }
371     }
372 }