ChunkedWriteHandler.java
/*
* Copyright 2012 The Netty Project
*
* The Netty Project licenses this file to you under the Apache License,
* version 2.0 (the "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at:
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*/
package io.netty.handler.stream;
import static io.netty.util.internal.ObjectUtil.checkPositive;
import io.netty.buffer.ByteBufAllocator;
import io.netty.buffer.Unpooled;
import io.netty.channel.Channel;
import io.netty.channel.ChannelDuplexHandler;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.ChannelProgressivePromise;
import io.netty.channel.ChannelPromise;
import io.netty.util.ReferenceCountUtil;
import io.netty.util.internal.logging.InternalLogger;
import io.netty.util.internal.logging.InternalLoggerFactory;
import java.nio.channels.ClosedChannelException;
import java.util.ArrayDeque;
import java.util.Queue;
/**
* A {@link ChannelHandler} that adds support for writing a large data stream
* asynchronously neither spending a lot of memory nor getting
* {@link OutOfMemoryError}. Large data streaming such as file
* transfer requires complicated state management in a {@link ChannelHandler}
* implementation. {@link ChunkedWriteHandler} manages such complicated states
* so that you can send a large data stream without difficulties.
* <p>
* To use {@link ChunkedWriteHandler} in your application, you have to insert
* a new {@link ChunkedWriteHandler} instance:
* <pre>
* {@link ChannelPipeline} p = ...;
* p.addLast("streamer", <b>new {@link ChunkedWriteHandler}()</b>);
* p.addLast("handler", new MyHandler());
* </pre>
* Once inserted, you can write a {@link ChunkedInput} so that the
* {@link ChunkedWriteHandler} can pick it up and fetch the content of the
* stream chunk by chunk and write the fetched chunk downstream:
* <pre>
* {@link Channel} ch = ...;
* ch.write(new {@link ChunkedFile}(new File("video.mkv"));
* </pre>
*
* <h3>Sending a stream which generates a chunk intermittently</h3>
*
* Some {@link ChunkedInput} generates a chunk on a certain event or timing.
* Such {@link ChunkedInput} implementation often returns {@code null} on
* {@link ChunkedInput#readChunk(ChannelHandlerContext)}, resulting in the indefinitely suspended
* transfer. To resume the transfer when a new chunk is available, you have to
* call {@link #resumeTransfer()}.
*/
public class ChunkedWriteHandler extends ChannelDuplexHandler {
private static final InternalLogger logger =
InternalLoggerFactory.getInstance(ChunkedWriteHandler.class);
private Queue<PendingWrite> queue;
private volatile ChannelHandlerContext ctx;
public ChunkedWriteHandler() {
}
/**
* @deprecated use {@link #ChunkedWriteHandler()}
*/
@Deprecated
public ChunkedWriteHandler(int maxPendingWrites) {
checkPositive(maxPendingWrites, "maxPendingWrites");
}
private void allocateQueue() {
if (queue == null) {
queue = new ArrayDeque<PendingWrite>();
}
}
private boolean queueIsEmpty() {
return queue == null || queue.isEmpty();
}
@Override
public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
this.ctx = ctx;
}
/**
* Continues to fetch the chunks from the input.
*/
public void resumeTransfer() {
final ChannelHandlerContext ctx = this.ctx;
if (ctx == null) {
return;
}
if (ctx.executor().inEventLoop()) {
resumeTransfer0(ctx);
} else {
// let the transfer resume on the next event loop round
ctx.executor().execute(new Runnable() {
@Override
public void run() {
resumeTransfer0(ctx);
}
});
}
}
private void resumeTransfer0(ChannelHandlerContext ctx) {
try {
doFlush(ctx);
} catch (Exception e) {
logger.warn("Unexpected exception while sending chunks.", e);
}
}
@Override
public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
if (!queueIsEmpty() || msg instanceof ChunkedInput) {
allocateQueue();
queue.add(new PendingWrite(msg, promise));
} else {
ctx.write(msg, promise);
}
}
@Override
public void flush(ChannelHandlerContext ctx) throws Exception {
doFlush(ctx);
}
@Override
public void channelInactive(ChannelHandlerContext ctx) throws Exception {
doFlush(ctx);
ctx.fireChannelInactive();
}
@Override
public void channelWritabilityChanged(ChannelHandlerContext ctx) throws Exception {
if (ctx.channel().isWritable()) {
// channel is writable again try to continue flushing
doFlush(ctx);
}
ctx.fireChannelWritabilityChanged();
}
private void discard(Throwable cause) {
if (queueIsEmpty()) {
return;
}
for (;;) {
PendingWrite currentWrite = queue.poll();
if (currentWrite == null) {
break;
}
Object message = currentWrite.msg;
if (message instanceof ChunkedInput) {
ChunkedInput<?> in = (ChunkedInput<?>) message;
boolean endOfInput;
long inputLength;
try {
endOfInput = in.isEndOfInput();
inputLength = in.length();
closeInput(in);
} catch (Exception e) {
closeInput(in);
currentWrite.fail(e);
logger.warn("ChunkedInput failed", e);
continue;
}
if (!endOfInput) {
if (cause == null) {
cause = new ClosedChannelException();
}
currentWrite.fail(cause);
} else {
currentWrite.success(inputLength);
}
} else {
if (cause == null) {
cause = new ClosedChannelException();
}
currentWrite.fail(cause);
}
}
}
private void doFlush(final ChannelHandlerContext ctx) {
final Channel channel = ctx.channel();
if (!channel.isActive()) {
discard(null);
return;
}
if (queueIsEmpty()) {
ctx.flush();
return;
}
boolean requiresFlush = true;
ByteBufAllocator allocator = ctx.alloc();
while (channel.isWritable()) {
final PendingWrite currentWrite = queue.peek();
if (currentWrite == null) {
break;
}
if (currentWrite.promise.isDone()) {
// This might happen e.g. in the case when a write operation
// failed, but there are still unconsumed chunks left.
// Most chunked input sources would stop generating chunks
// and report end of input, but this doesn't work with any
// source wrapped in HttpChunkedInput.
// Note, that we're not trying to release the message/chunks
// as this had to be done already by someone who resolved the
// promise (using ChunkedInput.close method).
// See https://github.com/netty/netty/issues/8700.
queue.remove();
continue;
}
final Object pendingMessage = currentWrite.msg;
if (pendingMessage instanceof ChunkedInput) {
final ChunkedInput<?> chunks = (ChunkedInput<?>) pendingMessage;
boolean endOfInput;
boolean suspend;
Object message = null;
try {
message = chunks.readChunk(allocator);
endOfInput = chunks.isEndOfInput();
// No need to suspend when reached at the end.
suspend = message == null && !endOfInput;
} catch (final Throwable t) {
queue.remove();
if (message != null) {
ReferenceCountUtil.release(message);
}
closeInput(chunks);
currentWrite.fail(t);
break;
}
if (suspend) {
// ChunkedInput.nextChunk() returned null and it has
// not reached at the end of input. Let's wait until
// more chunks arrive. Nothing to write or notify.
break;
}
if (message == null) {
// If message is null write an empty ByteBuf.
// See https://github.com/netty/netty/issues/1671
message = Unpooled.EMPTY_BUFFER;
}
if (endOfInput) {
// We need to remove the element from the queue before we call writeAndFlush() as this operation
// may cause an action that also touches the queue.
queue.remove();
}
// Flush each chunk to conserve memory
ChannelFuture f = ctx.writeAndFlush(message);
if (endOfInput) {
if (f.isDone()) {
handleEndOfInputFuture(f, chunks, currentWrite);
} else {
// Register a listener which will close the input once the write is complete.
// This is needed because the Chunk may have some resource bound that can not
// be closed before it's not written.
//
// See https://github.com/netty/netty/issues/303
f.addListener(new ChannelFutureListener() {
@Override
public void operationComplete(ChannelFuture future) {
handleEndOfInputFuture(future, chunks, currentWrite);
}
});
}
} else {
final boolean resume = !channel.isWritable();
if (f.isDone()) {
handleFuture(f, chunks, currentWrite, resume);
} else {
f.addListener(new ChannelFutureListener() {
@Override
public void operationComplete(ChannelFuture future) {
handleFuture(future, chunks, currentWrite, resume);
}
});
}
}
requiresFlush = false;
} else {
queue.remove();
ctx.write(pendingMessage, currentWrite.promise);
requiresFlush = true;
}
if (!channel.isActive()) {
discard(new ClosedChannelException());
break;
}
}
if (requiresFlush) {
ctx.flush();
}
}
private static void handleEndOfInputFuture(ChannelFuture future, ChunkedInput<?> input, PendingWrite currentWrite) {
if (!future.isSuccess()) {
closeInput(input);
currentWrite.fail(future.cause());
} else {
// read state of the input in local variables before closing it
long inputProgress = input.progress();
long inputLength = input.length();
closeInput(input);
currentWrite.progress(inputProgress, inputLength);
currentWrite.success(inputLength);
}
}
private void handleFuture(ChannelFuture future, ChunkedInput<?> input, PendingWrite currentWrite, boolean resume) {
if (!future.isSuccess()) {
closeInput(input);
currentWrite.fail(future.cause());
} else {
currentWrite.progress(input.progress(), input.length());
if (resume && future.channel().isWritable()) {
resumeTransfer();
}
}
}
private static void closeInput(ChunkedInput<?> chunks) {
try {
chunks.close();
} catch (Throwable t) {
logger.warn("Failed to close a ChunkedInput.", t);
}
}
private static final class PendingWrite {
final Object msg;
final ChannelPromise promise;
PendingWrite(Object msg, ChannelPromise promise) {
this.msg = msg;
this.promise = promise;
}
void fail(Throwable cause) {
ReferenceCountUtil.release(msg);
promise.tryFailure(cause);
}
void success(long total) {
if (promise.isDone()) {
// No need to notify the progress or fulfill the promise because it's done already.
return;
}
progress(total, total);
promise.trySuccess();
}
void progress(long progress, long total) {
if (promise instanceof ChannelProgressivePromise) {
((ChannelProgressivePromise) promise).tryProgress(progress, total);
}
}
}
}