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 org.jboss.netty.buffer.ChannelBuffers;
19 import org.jboss.netty.channel.Channel;
20 import org.jboss.netty.channel.ChannelDownstreamHandler;
21 import org.jboss.netty.channel.ChannelEvent;
22 import org.jboss.netty.channel.ChannelFuture;
23 import org.jboss.netty.channel.ChannelFutureListener;
24 import org.jboss.netty.channel.ChannelHandler;
25 import org.jboss.netty.channel.ChannelHandlerContext;
26 import org.jboss.netty.channel.ChannelPipeline;
27 import org.jboss.netty.channel.ChannelStateEvent;
28 import org.jboss.netty.channel.ChannelUpstreamHandler;
29 import org.jboss.netty.channel.LifeCycleAwareChannelHandler;
30 import org.jboss.netty.channel.MessageEvent;
31 import org.jboss.netty.logging.InternalLogger;
32 import org.jboss.netty.logging.InternalLoggerFactory;
33
34 import java.io.IOException;
35 import java.nio.channels.ClosedChannelException;
36 import java.util.Queue;
37 import java.util.concurrent.ConcurrentLinkedQueue;
38 import java.util.concurrent.atomic.AtomicBoolean;
39
40 import static org.jboss.netty.channel.Channels.*;
41
42 /**
43 * A {@link ChannelHandler} that adds support for writing a large data stream
44 * asynchronously neither spending a lot of memory nor getting
45 * {@link OutOfMemoryError}. Large data streaming such as file
46 * transfer requires complicated state management in a {@link ChannelHandler}
47 * implementation. {@link ChunkedWriteHandler} manages such complicated states
48 * so that you can send a large data stream without difficulties.
49 * <p>
50 * To use {@link ChunkedWriteHandler} in your application, you have to insert
51 * a new {@link ChunkedWriteHandler} instance:
52 * <pre>
53 * {@link ChannelPipeline} p = ...;
54 * p.addLast("streamer", <b>new {@link ChunkedWriteHandler}()</b>);
55 * p.addLast("handler", new MyHandler());
56 * </pre>
57 * Once inserted, you can write a {@link ChunkedInput} so that the
58 * {@link ChunkedWriteHandler} can pick it up and fetch the content of the
59 * stream chunk by chunk and write the fetched chunk downstream:
60 * <pre>
61 * {@link Channel} ch = ...;
62 * ch.write(new {@link ChunkedFile}(new File("video.mkv"));
63 * </pre>
64 *
65 * <h3>Sending a stream which generates a chunk intermittently</h3>
66 *
67 * Some {@link ChunkedInput} generates a chunk on a certain event or timing.
68 * Such {@link ChunkedInput} implementation often returns {@code null} on
69 * {@link ChunkedInput#nextChunk()}, resulting in the indefinitely suspended
70 * transfer. To resume the transfer when a new chunk is available, you have to
71 * call {@link #resumeTransfer()}.
72 * @apiviz.landmark
73 * @apiviz.has org.jboss.netty.handler.stream.ChunkedInput oneway - - reads from
74 */
75 public class ChunkedWriteHandler
76 implements ChannelUpstreamHandler, ChannelDownstreamHandler, LifeCycleAwareChannelHandler {
77
78 private static final InternalLogger logger =
79 InternalLoggerFactory.getInstance(ChunkedWriteHandler.class);
80
81 private final Queue<MessageEvent> queue = new ConcurrentLinkedQueue<MessageEvent>();
82
83 private volatile ChannelHandlerContext ctx;
84 private final AtomicBoolean flush = new AtomicBoolean(false);
85 private MessageEvent currentEvent;
86 private volatile boolean flushNeeded;
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 Object m = currentEvent.getMessage();
162 if (m instanceof ChunkedInput) {
163 closeInput((ChunkedInput) m);
164 }
165
166 // Trigger a ClosedChannelException
167 if (cause == null) {
168 cause = new ClosedChannelException();
169 }
170 currentEvent.getFuture().setFailure(cause);
171 }
172
173 if (cause != null) {
174 if (fireNow) {
175 fireExceptionCaught(ctx.getChannel(), cause);
176 } else {
177 fireExceptionCaughtLater(ctx.getChannel(), cause);
178 }
179 }
180 }
181
182 private void flush(ChannelHandlerContext ctx, boolean fireNow) throws Exception {
183 boolean acquired;
184 final Channel channel = ctx.getChannel();
185 boolean suspend = false;
186 flushNeeded = true;
187 // use CAS to see if the have flush already running, if so we don't need to take futher actions
188 if (acquired = flush.compareAndSet(false, true)) {
189 flushNeeded = false;
190 try {
191 if (!channel.isConnected()) {
192 discard(ctx, fireNow);
193 return;
194 }
195
196 while (channel.isWritable()) {
197 if (currentEvent == null) {
198 currentEvent = queue.poll();
199 }
200
201 if (currentEvent == null) {
202 break;
203 }
204
205 if (currentEvent.getFuture().isDone()) {
206 // Skip the current request because the previous partial write
207 // attempt for the current request has been failed.
208 currentEvent = null;
209 } else {
210 final MessageEvent currentEvent = this.currentEvent;
211 Object m = currentEvent.getMessage();
212 if (m instanceof ChunkedInput) {
213 final ChunkedInput chunks = (ChunkedInput) m;
214 Object chunk;
215 boolean endOfInput;
216 try {
217 chunk = chunks.nextChunk();
218 endOfInput = chunks.isEndOfInput();
219 if (chunk == null) {
220 chunk = ChannelBuffers.EMPTY_BUFFER;
221 // No need to suspend when reached at the end.
222 suspend = !endOfInput;
223 } else {
224 suspend = false;
225 }
226 } catch (Throwable t) {
227 this.currentEvent = null;
228
229 currentEvent.getFuture().setFailure(t);
230 if (fireNow) {
231 fireExceptionCaught(ctx, t);
232 } else {
233 fireExceptionCaughtLater(ctx, t);
234 }
235
236 closeInput(chunks);
237 break;
238 }
239
240 if (suspend) {
241 // ChunkedInput.nextChunk() returned null and it has
242 // not reached at the end of input. Let's wait until
243 // more chunks arrive. Nothing to write or notify.
244 break;
245 } else {
246 ChannelFuture writeFuture;
247 if (endOfInput) {
248 this.currentEvent = null;
249 writeFuture = currentEvent.getFuture();
250
251 // Register a listener which will close the input once the write
252 // is complete. This is needed because the Chunk may have some
253 // resource bound that can not be closed before its not written
254 //
255 // See https://github.com/netty/netty/issues/303
256 writeFuture.addListener(new ChannelFutureListener() {
257
258 public void operationComplete(ChannelFuture future) throws Exception {
259 closeInput(chunks);
260 }
261 });
262 } else {
263 writeFuture = future(channel);
264 writeFuture.addListener(new ChannelFutureListener() {
265 public void operationComplete(ChannelFuture future) throws Exception {
266 if (!future.isSuccess()) {
267 currentEvent.getFuture().setFailure(future.getCause());
268 closeInput((ChunkedInput) currentEvent.getMessage());
269 }
270 }
271 });
272 }
273
274 write(
275 ctx, writeFuture, chunk,
276 currentEvent.getRemoteAddress());
277 }
278 } else {
279 this.currentEvent = null;
280 ctx.sendDownstream(currentEvent);
281 }
282 }
283
284 if (!channel.isConnected()) {
285 discard(ctx, fireNow);
286 return;
287 }
288 }
289 } finally {
290 // mark the flush as done
291 flush.set(false);
292 }
293 }
294
295 if (acquired && (!channel.isConnected() || channel.isWritable() && !queue.isEmpty() && !suspend
296 || flushNeeded)) {
297 flush(ctx, fireNow);
298 }
299 }
300
301 static void closeInput(ChunkedInput chunks) {
302 try {
303 chunks.close();
304 } catch (Throwable t) {
305 if (logger.isWarnEnabled()) {
306 logger.warn("Failed to close a chunked input.", t);
307 }
308 }
309 }
310
311 public void beforeAdd(ChannelHandlerContext ctx) throws Exception {
312 // nothing to do
313 }
314
315 public void afterAdd(ChannelHandlerContext ctx) throws Exception {
316 // nothing to do
317 }
318
319 public void beforeRemove(ChannelHandlerContext ctx) throws Exception {
320 // try to flush again a last time.
321 //
322 // See #304
323 flush(ctx, false);
324 }
325
326 // This method should not need any synchronization as the ChunkedWriteHandler will not receive any new events
327 public void afterRemove(ChannelHandlerContext ctx) throws Exception {
328 // Fail all MessageEvent's that are left. This is needed because otherwise we would never notify the
329 // ChannelFuture and the registered FutureListener. See #304
330 Throwable cause = null;
331 boolean fireExceptionCaught = false;
332
333 for (;;) {
334 MessageEvent currentEvent = this.currentEvent;
335
336 if (this.currentEvent == null) {
337 currentEvent = queue.poll();
338 } else {
339 this.currentEvent = null;
340 }
341
342 if (currentEvent == null) {
343 break;
344 }
345
346 Object m = currentEvent.getMessage();
347 if (m instanceof ChunkedInput) {
348 closeInput((ChunkedInput) m);
349 }
350
351 // Create exception
352 if (cause == null) {
353 cause = new IOException("Unable to flush event, discarding");
354 }
355 currentEvent.getFuture().setFailure(cause);
356 fireExceptionCaught = true;
357 }
358
359 if (fireExceptionCaught) {
360 fireExceptionCaughtLater(ctx.getChannel(), cause);
361 }
362 }
363 }