MessageAggregator.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.codec;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.ByteBufHolder;
import io.netty.buffer.CompositeByteBuf;
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.util.ReferenceCountUtil;
import java.util.List;
import static io.netty.buffer.Unpooled.EMPTY_BUFFER;
import static io.netty.util.internal.ObjectUtil.checkPositiveOrZero;
/**
* An abstract {@link ChannelHandler} that aggregates a series of message objects into a single aggregated message.
* <p>
* 'A series of messages' is composed of the following:
* <ul>
* <li>a single start message which optionally contains the first part of the content, and</li>
* <li>1 or more content messages.</li>
* </ul>
* The content of the aggregated message will be the merged content of the start message and its following content
* messages. If this aggregator encounters a content message where {@link #isLastContentMessage(ByteBufHolder)}
* return {@code true} for, the aggregator will finish the aggregation and produce the aggregated message and expect
* another start message.
* </p>
*
* @param <I> the type that covers both start message and content message
* @param <S> the type of the start message
* @param <C> the type of the content message (must be a subtype of {@link ByteBufHolder})
* @param <O> the type of the aggregated message (must be a subtype of {@code S} and {@link ByteBufHolder})
*/
public abstract class MessageAggregator<I, S, C extends ByteBufHolder, O extends ByteBufHolder>
extends MessageToMessageDecoder<I> {
private static final int DEFAULT_MAX_COMPOSITEBUFFER_COMPONENTS = 1024;
private final int maxContentLength;
private O currentMessage;
private boolean handlingOversizedMessage;
private int maxCumulationBufferComponents = DEFAULT_MAX_COMPOSITEBUFFER_COMPONENTS;
private ChannelHandlerContext ctx;
private ChannelFutureListener continueResponseWriteListener;
private boolean aggregating;
private boolean handleIncompleteAggregateDuringClose = true;
/**
* Creates a new instance.
*
* @param maxContentLength
* the maximum length of the aggregated content.
* If the length of the aggregated content exceeds this value,
* {@link #handleOversizedMessage(ChannelHandlerContext, Object)} will be called.
*/
protected MessageAggregator(int maxContentLength) {
validateMaxContentLength(maxContentLength);
this.maxContentLength = maxContentLength;
}
protected MessageAggregator(int maxContentLength, Class<? extends I> inboundMessageType) {
super(inboundMessageType);
validateMaxContentLength(maxContentLength);
this.maxContentLength = maxContentLength;
}
private static void validateMaxContentLength(int maxContentLength) {
checkPositiveOrZero(maxContentLength, "maxContentLength");
}
@Override
public boolean acceptInboundMessage(Object msg) throws Exception {
// No need to match last and full types because they are subset of first and middle types.
if (!super.acceptInboundMessage(msg)) {
return false;
}
@SuppressWarnings("unchecked")
I in = (I) msg;
if (isAggregated(in)) {
return false;
}
// NOTE: It's tempting to make this check only if aggregating is false. There are however
// side conditions in decode(...) in respect to large messages.
if (isStartMessage(in)) {
return true;
} else {
return aggregating && isContentMessage(in);
}
}
/**
* Returns {@code true} if and only if the specified message is a start message. Typically, this method is
* implemented as a single {@code return} statement with {@code instanceof}:
* <pre>
* return msg instanceof MyStartMessage;
* </pre>
*/
protected abstract boolean isStartMessage(I msg) throws Exception;
/**
* Returns {@code true} if and only if the specified message is a content message. Typically, this method is
* implemented as a single {@code return} statement with {@code instanceof}:
* <pre>
* return msg instanceof MyContentMessage;
* </pre>
*/
protected abstract boolean isContentMessage(I msg) throws Exception;
/**
* Returns {@code true} if and only if the specified message is the last content message. Typically, this method is
* implemented as a single {@code return} statement with {@code instanceof}:
* <pre>
* return msg instanceof MyLastContentMessage;
* </pre>
* or with {@code instanceof} and boolean field check:
* <pre>
* return msg instanceof MyContentMessage && msg.isLastFragment();
* </pre>
*/
protected abstract boolean isLastContentMessage(C msg) throws Exception;
/**
* Returns {@code true} if and only if the specified message is already aggregated. If this method returns
* {@code true}, this handler will simply forward the message to the next handler as-is.
*/
protected abstract boolean isAggregated(I msg) throws Exception;
/**
* Returns the maximum allowed length of the aggregated message in bytes.
*/
public final int maxContentLength() {
return maxContentLength;
}
/**
* Returns the maximum number of components in the cumulation buffer. If the number of
* the components in the cumulation buffer exceeds this value, the components of the
* cumulation buffer are consolidated into a single component, involving memory copies.
* The default value of this property is {@value #DEFAULT_MAX_COMPOSITEBUFFER_COMPONENTS}.
*/
public final int maxCumulationBufferComponents() {
return maxCumulationBufferComponents;
}
/**
* Sets the maximum number of components in the cumulation buffer. If the number of
* the components in the cumulation buffer exceeds this value, the components of the
* cumulation buffer are consolidated into a single component, involving memory copies.
* The default value of this property is {@value #DEFAULT_MAX_COMPOSITEBUFFER_COMPONENTS}
* and its minimum allowed value is {@code 2}.
*/
public final void setMaxCumulationBufferComponents(int maxCumulationBufferComponents) {
if (maxCumulationBufferComponents < 2) {
throw new IllegalArgumentException(
"maxCumulationBufferComponents: " + maxCumulationBufferComponents +
" (expected: >= 2)");
}
if (ctx == null) {
this.maxCumulationBufferComponents = maxCumulationBufferComponents;
} else {
throw new IllegalStateException(
"decoder properties cannot be changed once the decoder is added to a pipeline.");
}
}
/**
* @deprecated This method will be removed in future releases.
*/
@Deprecated
public final boolean isHandlingOversizedMessage() {
return handlingOversizedMessage;
}
protected final ChannelHandlerContext ctx() {
if (ctx == null) {
throw new IllegalStateException("not added to a pipeline yet");
}
return ctx;
}
@Override
protected void decode(final ChannelHandlerContext ctx, I msg, List<Object> out) throws Exception {
if (isStartMessage(msg)) {
aggregating = true;
handlingOversizedMessage = false;
if (currentMessage != null) {
currentMessage.release();
currentMessage = null;
throw new MessageAggregationException();
}
@SuppressWarnings("unchecked")
S m = (S) msg;
// Send the continue response if necessary (e.g. 'Expect: 100-continue' header)
// Check before content length. Failing an expectation may result in a different response being sent.
Object continueResponse = newContinueResponse(m, maxContentLength, ctx.pipeline());
if (continueResponse != null) {
// Cache the write listener for reuse.
ChannelFutureListener listener = continueResponseWriteListener;
if (listener == null) {
continueResponseWriteListener = listener = new ChannelFutureListener() {
@Override
public void operationComplete(ChannelFuture future) throws Exception {
if (!future.isSuccess()) {
ctx.fireExceptionCaught(future.cause());
}
}
};
}
// Make sure to call this before writing, otherwise reference counts may be invalid.
boolean closeAfterWrite = closeAfterContinueResponse(continueResponse);
handlingOversizedMessage = ignoreContentAfterContinueResponse(continueResponse);
final ChannelFuture future = ctx.writeAndFlush(continueResponse).addListener(listener);
if (closeAfterWrite) {
handleIncompleteAggregateDuringClose = false;
future.addListener(ChannelFutureListener.CLOSE);
return;
}
if (handlingOversizedMessage) {
return;
}
} else if (isContentLengthInvalid(m, maxContentLength)) {
// if content length is set, preemptively close if it's too large
invokeHandleOversizedMessage(ctx, m);
return;
}
if (m instanceof DecoderResultProvider && !((DecoderResultProvider) m).decoderResult().isSuccess()) {
O aggregated;
if (m instanceof ByteBufHolder) {
aggregated = beginAggregation(m, ((ByteBufHolder) m).content().retain());
} else {
aggregated = beginAggregation(m, EMPTY_BUFFER);
}
finishAggregation0(aggregated);
out.add(aggregated);
return;
}
// A streamed message - initialize the cumulative buffer, and wait for incoming chunks.
CompositeByteBuf content = ctx.alloc().compositeBuffer(maxCumulationBufferComponents);
if (m instanceof ByteBufHolder) {
appendPartialContent(content, ((ByteBufHolder) m).content());
}
currentMessage = beginAggregation(m, content);
} else if (isContentMessage(msg)) {
if (currentMessage == null) {
// it is possible that a TooLongFrameException was already thrown but we can still discard data
// until the begging of the next request/response.
return;
}
// Merge the received chunk into the content of the current message.
CompositeByteBuf content = (CompositeByteBuf) currentMessage.content();
@SuppressWarnings("unchecked")
final C m = (C) msg;
// Handle oversized message.
if (content.readableBytes() > maxContentLength - m.content().readableBytes()) {
// By convention, full message type extends first message type.
@SuppressWarnings("unchecked")
S s = (S) currentMessage;
invokeHandleOversizedMessage(ctx, s);
return;
}
// Append the content of the chunk.
appendPartialContent(content, m.content());
// Give the subtypes a chance to merge additional information such as trailing headers.
aggregate(currentMessage, m);
final boolean last;
if (m instanceof DecoderResultProvider) {
DecoderResult decoderResult = ((DecoderResultProvider) m).decoderResult();
if (!decoderResult.isSuccess()) {
if (currentMessage instanceof DecoderResultProvider) {
((DecoderResultProvider) currentMessage).setDecoderResult(
DecoderResult.failure(decoderResult.cause()));
}
last = true;
} else {
last = isLastContentMessage(m);
}
} else {
last = isLastContentMessage(m);
}
if (last) {
finishAggregation0(currentMessage);
// All done
out.add(currentMessage);
currentMessage = null;
}
} else {
throw new MessageAggregationException();
}
}
private static void appendPartialContent(CompositeByteBuf content, ByteBuf partialContent) {
if (partialContent.isReadable()) {
content.addComponent(true, partialContent.retain());
}
}
/**
* Determine if the message {@code start}'s content length is known, and if it greater than
* {@code maxContentLength}.
* @param start The message which may indicate the content length.
* @param maxContentLength The maximum allowed content length.
* @return {@code true} if the message {@code start}'s content length is known, and if it greater than
* {@code maxContentLength}. {@code false} otherwise.
*/
protected abstract boolean isContentLengthInvalid(S start, int maxContentLength) throws Exception;
/**
* Returns the 'continue response' for the specified start message if necessary. For example, this method is
* useful to handle an HTTP 100-continue header.
*
* @return the 'continue response', or {@code null} if there's no message to send
*/
protected abstract Object newContinueResponse(S start, int maxContentLength, ChannelPipeline pipeline)
throws Exception;
/**
* Determine if the channel should be closed after the result of
* {@link #newContinueResponse(Object, int, ChannelPipeline)} is written.
* @param msg The return value from {@link #newContinueResponse(Object, int, ChannelPipeline)}.
* @return {@code true} if the channel should be closed after the result of
* {@link #newContinueResponse(Object, int, ChannelPipeline)} is written. {@code false} otherwise.
*/
protected abstract boolean closeAfterContinueResponse(Object msg) throws Exception;
/**
* Determine if all objects for the current request/response should be ignored or not.
* Messages will stop being ignored the next time {@link #isContentMessage(Object)} returns {@code true}.
*
* @param msg The return value from {@link #newContinueResponse(Object, int, ChannelPipeline)}.
* @return {@code true} if all objects for the current request/response should be ignored or not.
* {@code false} otherwise.
*/
protected abstract boolean ignoreContentAfterContinueResponse(Object msg) throws Exception;
/**
* Creates a new aggregated message from the specified start message and the specified content. If the start
* message implements {@link ByteBufHolder}, its content is appended to the specified {@code content}.
* This aggregator will continue to append the received content to the specified {@code content}.
*/
protected abstract O beginAggregation(S start, ByteBuf content) throws Exception;
/**
* Transfers the information provided by the specified content message to the specified aggregated message.
* Note that the content of the specified content message has been appended to the content of the specified
* aggregated message already, so that you don't need to. Use this method to transfer the additional information
* that the content message provides to {@code aggregated}.
*/
protected void aggregate(O aggregated, C content) throws Exception { }
private void finishAggregation0(O aggregated) throws Exception {
aggregating = false;
finishAggregation(aggregated);
}
/**
* Invoked when the specified {@code aggregated} message is about to be passed to the next handler in the pipeline.
*/
protected void finishAggregation(O aggregated) throws Exception { }
private void invokeHandleOversizedMessage(ChannelHandlerContext ctx, S oversized) throws Exception {
handlingOversizedMessage = true;
currentMessage = null;
handleIncompleteAggregateDuringClose = false;
try {
handleOversizedMessage(ctx, oversized);
} finally {
// Release the message in case it is a full one.
ReferenceCountUtil.release(oversized);
}
}
/**
* Invoked when an incoming request exceeds the maximum content length. The default behvaior is to trigger an
* {@code exceptionCaught()} event with a {@link TooLongFrameException}.
*
* @param ctx the {@link ChannelHandlerContext}
* @param oversized the accumulated message up to this point, whose type is {@code S} or {@code O}
*/
protected void handleOversizedMessage(ChannelHandlerContext ctx, S oversized) throws Exception {
ctx.fireExceptionCaught(
new TooLongFrameException("content length exceeded " + maxContentLength() + " bytes."));
}
@Override
public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
// We might need keep reading the channel until the full message is aggregated.
//
// See https://github.com/netty/netty/issues/6583
if (currentMessage != null && !ctx.channel().config().isAutoRead()) {
ctx.read();
}
ctx.fireChannelReadComplete();
}
@Override
public void channelInactive(ChannelHandlerContext ctx) throws Exception {
if (aggregating && handleIncompleteAggregateDuringClose) {
ctx.fireExceptionCaught(
new PrematureChannelClosureException("Channel closed while still aggregating message"));
}
try {
// release current message if it is not null as it may be a left-over
super.channelInactive(ctx);
} finally {
releaseCurrentMessage();
}
}
@Override
public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
this.ctx = ctx;
}
@Override
public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
try {
super.handlerRemoved(ctx);
} finally {
// release current message if it is not null as it may be a left-over as there is not much more we can do in
// this case
releaseCurrentMessage();
}
}
private void releaseCurrentMessage() {
if (currentMessage != null) {
currentMessage.release();
currentMessage = null;
handlingOversizedMessage = false;
aggregating = false;
}
}
}