Motivation:
This PR (unfortunately) does 4 things:
1) Add outbound flow control to the Http2MultiplexCodec:
The HTTP/2 child channel API should interact with HTTP/2 outbound/remote flow control. That is,
if a H2 stream used up all its flow control window, the corresponding child channel should be
marked unwritable and a writability-changed event should be fired. Similarly, a unwritable
child channel should be marked writable and a writability-event should be fired, once a
WINDOW_UPDATE frame has been received. The changes are (mostly) contained in ChannelOutboundBuffer,
AbstractHttp2StreamChannel and Http2MultiplexCodec.
2) Introduce a Http2Stream2 object, that is used instead of stream identifiers on stream frames. A
Http2Stream2 object allows an application to attach state to it, and so a application handler
no longer needs to maintain stream state (i.e. in a map(id -> state)) himself.
3) Remove stream state events, which are no longer necessary due to the introduction of Http2Stream2.
Also those stream state events have been found hard and complex to work with, when porting gRPC
to the Http2FrameCodec.
4) Add support for HTTP/2 frames that have not yet been implemented, like PING and SETTINGS. Also add
a Http2FrameCodecBuilder that exposes options from the Http2ConnectionHandler API that couldn't else
be used with the frame codec, like buffering outbound streams, window update ratio, frame logger, etc.
Modifications:
1) A child channel's writability and a H2 stream's outbound flow control window interact, as described
in the motivation. A channel handler is free to ignore the channel's writability, in which case the
parent channel is reponsible for buffering writes until a WINDOW_UPDATE is received.
The connection-level flow control window is ignored for now. That is, a child channel's writability
is only affected by the stream-level flow control window. So a child channel could be marked writable,
even though the connection-level flow control window is zero.
2) Modify Http2StreamFrame and the Http2FrameCodec to take a Http2Stream2 object intstead of a primitive
integer. Introduce a special Http2ChannelDuplexHandler that has newStream() and forEachActiveStream()
methods. It's recommended for a user to extend from this handler, to use those advanced features.
3) As explained in the documentation, a new inbound stream active can be detected by checking if the
Http2Stream2.managedState() of a Http2HeadersFrame is null. An outbound stream active can be detected
by adding a listener to the ChannelPromise of the write of the first Http2HeadersFrame. A stream
closed event can be listened to by adding a listener to the Http2Stream2.closeFuture().
4) Add a simple Http2FrameCodecBuilder and implement the missing frame types.
Result:
1) The Http2MultiplexCodec supports outbound flow control.
2) The Http2FrameCodec API makes it easy for a user to manage custom stream specific state and to create
new outbound streams.
3) The Http2FrameCodec API is much cleaner and easier to work with. Hacks like the ChannelCarryingHeadersFrame
are no longer necessary.
4) The Http2FrameCodec now also supports PING and SETTINGS frames. The Http2FrameCodecBuilder allows the Http2FrameCodec
to use some of the rich features of the Http2ConnectionHandler API.
Motivation:
codec-http2 has some helper methods to write to ByteBuf in a big endian fashion. This is the default memory structure for ByteBuf so these helper methods are not necessary.
Modifications:
- remove writeUnsignedInt and writeUnsignedShort
Result:
codec-http2 has less ByteBuf helper methods which are not necessary.
Motivation:
Some codecs should be considered unstable as these are relative new. For this purpose we should introduce an annotation which these codecs should us to be marked as unstable in terms of API.
Modifications:
- Add UnstableApi annotation and use it on codecs that are not stable
- Move http2.hpack to http2.internal.hpack as it is internal.
Result:
Better document unstable APIs.
Motivation:
Http2CodecUtils has some static variables which are defined as Strings instead of CharSequence. One of these defines is used as a header name and should be AsciiString.
Modifications:
- Change the String defines in Http2CodecUtils to CharSequence
Result:
Types are more consistently using CharSequence and adding the upgrade header will require less work.
Motivation:
It would be useful to support the Java `Map` interface in our primitive maps.
Modifications:
Renamed current methods to "pXXX", where p is short for "primitive". Made the template for all primitive maps extend the appropriate Map interface.
Result:
Fixes#3970
Motivation:
Our HTTP/2 implementation sometimes uses hard-coded handler names when
adding/removing a handler to/from a pipeline. It's not really a good
idea because it can easily result in name clashes. Unless there is a
good reason, we need to use the reference to the handlers
Modifications:
- Allow null as a handler name for Http2Client/ServerUpgradeCodec
- Use null as the default upgrade handler name
- Do not use handler name strings in some test cases and examples
Result:
Fixes#3815
Motivation:
Now that we have a CharObjectHashMap, we should change Http2Settings to use it.
Modifications:
Changed Http2Settings to extend CharObjectHashMap rather than IntObjectHashMap.
Result:
Http2Settings uses less memory to store keys.
Motivation:
HTTP/2 codec was implemented in master branch.
Since, master is not yet stable and will be some time before it gets released, backporting it to 4.1, enables people to use the codec with a stable netty version.
Modification:
The code has been copied from master branch as is, with minor modifications to suit the `ChannelHandler` API in 4.x.
Apart from that change, there are two backward incompatible API changes included, namely,
- Added an abstract method:
`public abstract Map.Entry<CharSequence, CharSequence> forEachEntry(EntryVisitor<CharSequence> visitor)
throws Exception;`
to `HttpHeaders` and implemented the same in `DefaultHttpHeaders` as a delegate to the internal `TextHeader` instance.
- Added a method:
`FullHttpMessage copy(ByteBuf newContent);`
in `FullHttpMessage` with the implementations copied from relevant places in the master branch.
- Added missing abstract method related to setting/adding short values to `HttpHeaders`
Result:
HTTP/2 codec can be used with netty 4.1
