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/*
* Copyright 2015 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:
*
* http://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.http2;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.ByteBufUtil;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelPromise;
import io.netty.util.ReferenceCountUtil;
import io.netty.util.internal.UnstableApi;
import java.util.ArrayDeque;
import java.util.Iterator;
import java.util.Map;
import java.util.Queue;
import java.util.TreeMap;
import static io.netty.handler.codec.http2.Http2CodecUtil.SMALLEST_MAX_CONCURRENT_STREAMS;
import static io.netty.handler.codec.http2.Http2Error.PROTOCOL_ERROR;
import static io.netty.handler.codec.http2.Http2Exception.connectionError;
/**
* Implementation of a {@link Http2ConnectionEncoder} that dispatches all method call to another
* {@link Http2ConnectionEncoder}, until {@code SETTINGS_MAX_CONCURRENT_STREAMS} is reached.
*
* When this limit is hit, instead of rejecting any new streams this implementation buffers newly
* created streams and their corresponding frames. Once an active stream gets closed or the maximum
* number of concurrent streams is increased, this encoder will automatically try to empty its
* buffer and create as many new streams as possible.
*
*
* If a {@code GOAWAY} frame is received from the remote endpoint, all buffered writes for streams
* with an ID less than the specified {@code lastStreamId} will immediately fail with a
* {@link Http2GoAwayException}.
*
*
* If the channel/encoder gets closed, all new and buffered writes will immediately fail with a
* {@link Http2ChannelClosedException}.
*
* This implementation makes the buffering mostly transparent and is expected to be used as a
* drop-in decorator of {@link DefaultHttp2ConnectionEncoder}.
*
*/
@UnstableApi
public class StreamBufferingEncoder extends DecoratingHttp2ConnectionEncoder {
/**
* Thrown if buffered streams are terminated due to this encoder being closed.
*/
public static final class Http2ChannelClosedException extends Http2Exception {
private static final long serialVersionUID = 4768543442094476971L;
public Http2ChannelClosedException() {
super(Http2Error.REFUSED_STREAM, "Connection closed");
}
}
/**
* Thrown by {@link StreamBufferingEncoder} if buffered streams are terminated due to
* receipt of a {@code GOAWAY}.
*/
public static final class Http2GoAwayException extends Http2Exception {
private static final long serialVersionUID = 1326785622777291198L;
private final int lastStreamId;
private final long errorCode;
private final byte[] debugData;
public Http2GoAwayException(int lastStreamId, long errorCode, byte[] debugData) {
super(Http2Error.STREAM_CLOSED);
this.lastStreamId = lastStreamId;
this.errorCode = errorCode;
this.debugData = debugData;
}
public int lastStreamId() {
return lastStreamId;
}
public long errorCode() {
return errorCode;
}
public byte[] debugData() {
return debugData;
}
}
/**
* Buffer for any streams and corresponding frames that could not be created due to the maximum
* concurrent stream limit being hit.
*/
private final TreeMap pendingStreams = new TreeMap();
private int maxConcurrentStreams;
private boolean closed;
public StreamBufferingEncoder(Http2ConnectionEncoder delegate) {
this(delegate, SMALLEST_MAX_CONCURRENT_STREAMS);
}
public StreamBufferingEncoder(Http2ConnectionEncoder delegate, int initialMaxConcurrentStreams) {
super(delegate);
this.maxConcurrentStreams = initialMaxConcurrentStreams;
connection().addListener(new Http2ConnectionAdapter() {
@Override
public void onGoAwayReceived(int lastStreamId, long errorCode, ByteBuf debugData) {
cancelGoAwayStreams(lastStreamId, errorCode, debugData);
}
@Override
public void onStreamClosed(Http2Stream stream) {
tryCreatePendingStreams();
}
});
}
/**
* Indicates the number of streams that are currently buffered, awaiting creation.
*/
public int numBufferedStreams() {
return pendingStreams.size();
}
@Override
public ChannelFuture writeHeaders(ChannelHandlerContext ctx, int streamId, Http2Headers headers,
int padding, boolean endStream, ChannelPromise promise) {
return writeHeaders(ctx, streamId, headers, 0, Http2CodecUtil.DEFAULT_PRIORITY_WEIGHT,
false, padding, endStream, promise);
}
@Override
public ChannelFuture writeHeaders(ChannelHandlerContext ctx, int streamId, Http2Headers headers,
int streamDependency, short weight, boolean exclusive,
int padding, boolean endOfStream, ChannelPromise promise) {
if (closed) {
return promise.setFailure(new Http2ChannelClosedException());
}
if (isExistingStream(streamId) || connection().goAwayReceived()) {
return super.writeHeaders(ctx, streamId, headers, streamDependency, weight,
exclusive, padding, endOfStream, promise);
}
if (canCreateStream()) {
return super.writeHeaders(ctx, streamId, headers, streamDependency, weight,
exclusive, padding, endOfStream, promise);
}
PendingStream pendingStream = pendingStreams.get(streamId);
if (pendingStream == null) {
pendingStream = new PendingStream(ctx, streamId);
pendingStreams.put(streamId, pendingStream);
}
pendingStream.frames.add(new HeadersFrame(headers, streamDependency, weight, exclusive,
padding, endOfStream, promise));
return promise;
}
@Override
public ChannelFuture writeRstStream(ChannelHandlerContext ctx, int streamId, long errorCode,
ChannelPromise promise) {
if (isExistingStream(streamId)) {
return super.writeRstStream(ctx, streamId, errorCode, promise);
}
// Since the delegate doesn't know about any buffered streams we have to handle cancellation
// of the promises and releasing of the ByteBufs here.
PendingStream stream = pendingStreams.remove(streamId);
if (stream != null) {
// Sending a RST_STREAM to a buffered stream will succeed the promise of all frames
// associated with the stream, as sending a RST_STREAM means that someone "doesn't care"
// about the stream anymore and thus there is not point in failing the promises and invoking
// error handling routines.
stream.close(null);
promise.setSuccess();
} else {
promise.setFailure(connectionError(PROTOCOL_ERROR, "Stream does not exist %d", streamId));
}
return promise;
}
@Override
public ChannelFuture writeData(ChannelHandlerContext ctx, int streamId, ByteBuf data,
int padding, boolean endOfStream, ChannelPromise promise) {
if (isExistingStream(streamId)) {
return super.writeData(ctx, streamId, data, padding, endOfStream, promise);
}
PendingStream pendingStream = pendingStreams.get(streamId);
if (pendingStream != null) {
pendingStream.frames.add(new DataFrame(data, padding, endOfStream, promise));
} else {
ReferenceCountUtil.safeRelease(data);
promise.setFailure(connectionError(PROTOCOL_ERROR, "Stream does not exist %d", streamId));
}
return promise;
}
@Override
public void remoteSettings(Http2Settings settings) throws Http2Exception {
// Need to let the delegate decoder handle the settings first, so that it sees the
// new setting before we attempt to create any new streams.
super.remoteSettings(settings);
// Get the updated value for SETTINGS_MAX_CONCURRENT_STREAMS.
maxConcurrentStreams = connection().local().maxActiveStreams();
// Try to create new streams up to the new threshold.
tryCreatePendingStreams();
}
@Override
public void close() {
try {
if (!closed) {
closed = true;
// Fail all buffered streams.
Http2ChannelClosedException e = new Http2ChannelClosedException();
while (!pendingStreams.isEmpty()) {
PendingStream stream = pendingStreams.pollFirstEntry().getValue();
stream.close(e);
}
}
} finally {
super.close();
}
}
private void tryCreatePendingStreams() {
while (!pendingStreams.isEmpty() && canCreateStream()) {
Map.Entry entry = pendingStreams.pollFirstEntry();
PendingStream pendingStream = entry.getValue();
try {
pendingStream.sendFrames();
} catch (Throwable t) {
pendingStream.close(t);
}
}
}
private void cancelGoAwayStreams(int lastStreamId, long errorCode, ByteBuf debugData) {
Iterator iter = pendingStreams.values().iterator();
Exception e = new Http2GoAwayException(lastStreamId, errorCode, ByteBufUtil.getBytes(debugData));
while (iter.hasNext()) {
PendingStream stream = iter.next();
if (stream.streamId > lastStreamId) {
iter.remove();
stream.close(e);
}
}
}
/**
* Determines whether or not we're allowed to create a new stream right now.
*/
private boolean canCreateStream() {
return connection().local().numActiveStreams() < maxConcurrentStreams;
}
private boolean isExistingStream(int streamId) {
return streamId <= connection().local().lastStreamCreated();
}
private static final class PendingStream {
final ChannelHandlerContext ctx;
final int streamId;
final Queue frames = new ArrayDeque(2);
PendingStream(ChannelHandlerContext ctx, int streamId) {
this.ctx = ctx;
this.streamId = streamId;
}
void sendFrames() {
for (Frame frame : frames) {
frame.send(ctx, streamId);
}
}
void close(Throwable t) {
for (Frame frame : frames) {
frame.release(t);
}
}
}
private abstract static class Frame {
final ChannelPromise promise;
Frame(ChannelPromise promise) {
this.promise = promise;
}
/**
* Release any resources (features, buffers, ...) associated with the frame.
*/
void release(Throwable t) {
if (t == null) {
promise.setSuccess();
} else {
promise.setFailure(t);
}
}
abstract void send(ChannelHandlerContext ctx, int streamId);
}
private final class HeadersFrame extends Frame {
final Http2Headers headers;
final int streamDependency;
final short weight;
final boolean exclusive;
final int padding;
final boolean endOfStream;
HeadersFrame(Http2Headers headers, int streamDependency, short weight, boolean exclusive,
int padding, boolean endOfStream, ChannelPromise promise) {
super(promise);
this.headers = headers;
this.streamDependency = streamDependency;
this.weight = weight;
this.exclusive = exclusive;
this.padding = padding;
this.endOfStream = endOfStream;
}
@Override
void send(ChannelHandlerContext ctx, int streamId) {
writeHeaders(ctx, streamId, headers, streamDependency, weight, exclusive, padding, endOfStream, promise);
}
}
private final class DataFrame extends Frame {
final ByteBuf data;
final int padding;
final boolean endOfStream;
DataFrame(ByteBuf data, int padding, boolean endOfStream, ChannelPromise promise) {
super(promise);
this.data = data;
this.padding = padding;
this.endOfStream = endOfStream;
}
@Override
void release(Throwable t) {
super.release(t);
ReferenceCountUtil.safeRelease(data);
}
@Override
void send(ChannelHandlerContext ctx, int streamId) {
writeData(ctx, streamId, data, padding, endOfStream, promise);
}
}
}