Motivation:
In the past we had the following class hierarchy:
Http2ConnectionHandler --- Http2FrameCodec -- Http2MultiplexCodec
This hierarchy makes it impossible to plug in any code that would like to act on Http2Frame and Http2StreamFrame which can be quite useful for various situations (like metrics, logging etc). Beside this it also made the implementtion very hacky. To allow easier maintainance and also allow more flexible costumizations we should split Http2MultiplexCodec and Http2FrameCode.
Modifications:
- Introduce Http2MultiplexHandler (which is a replacement for Http2MultiplexCodec when used together with Http2FrameCodec)
- Mark Http2MultiplexCodecBuilder and Http2MultiplexCodec as deprecated. People should use Http2FrameCodecBuilder / Http2FrameCodec together with Http2MultiplexHandlder in the future
- Adjust / Add tests
- Adjust examples
Result:
More flexible usage possible and less hacky / coupled implementation for http2 multiplexing
Motivation:
Http2ConnectionHandler#close(..) always runs the GOAWAY and graceful close
logic. This coupling means that a user would have to override
Http2ConnectionHandler#close(..) to modify the behavior, and the
Http2FrameCodec and Http2MultiplexCodec are not extendable so you cannot
override at this layer. Ideally we can totally decouple the close(..) of the
transport and the GOAWAY graceful closure process completely, but to preserve
backwards compatibility we can add an opt-out option to decouple where the
application is responsible for sending a GOAWAY with error code equal to
NO_ERROR as described in https://tools.ietf.org/html/rfc7540#section-6.8 in
order to initiate graceful close.
Modifications:
- Http2ConnectionHandler supports an additional boolean constructor argument to
opt out of close(..) going through the graceful close path.
- Http2FrameCodecBuilder and Http2MultiplexCodec expose
gracefulShutdownTimeoutMillis but do not hook them up properly. Since these
are already exposed we should hook them up and make sure the timeout is applied
properly.
- Http2ConnectionHandler's goAway(..) method from Http2LifecycleManager should
initiate the graceful closure process after writing a GOAWAY frame if the error
code is NO_ERROR. This means that writing a Http2GoAwayFrame from
Http2FrameCodec will initiate graceful close.
Result:
Http2ConnectionHandler#close(..) can now be decoupled from the graceful close
process, and immediately close the underlying transport if desired.
Motivation:
The HTTP/2 codec will synchronously respond to a SETTINGS frame with a SETTINGS
ACK before the application sees the SETTINGS frame. The application may need to
adjust its state depending upon what is in the SETTINGS frame before applying
the remote settings and responding with an ACK (e.g. to adjust for max
concurrent streams). In order to accomplish this the HTTP/2 codec should allow
for the application to opt-in to sending the SETTINGS ACK.
Modifications:
- DefaultHttp2ConnectionDecoder should support a mode where SETTINGS frames can
be queued instead of immediately applying and ACKing.
- DefaultHttp2ConnectionEncoder should attempt to poll from the queue (if it
exists) to apply the earliest received but not yet ACKed SETTINGS frame.
- AbstractHttp2ConnectionHandlerBuilder (and sub classes) should support a new
option to enable the application to opt-in to managing SETTINGS ACK.
Result:
HTTP/2 allows for asynchronous SETTINGS ACK managed by the application.
Motiviation:
Http2FrameCodecTest and Http2MultiplexCodecTest were quite fragile and often not went through the whole pipeline which made testing sometimes hard and error-prone.
Modification:
- Refactor tests to have data flow through the whole pipeline and so made the test more robust (by testing the while implementation).
Result:
Easier to write tests for the codecs in the future and more robust testing in general.
Beside this it also fixes https://github.com/netty/netty/issues/6036.
Motivation:
Http2MultiplexCodec doesn't currently have an API for using the response
of a h2c upgrade request.
Modifications:
Add a new API to the Http2MultiplexCodecBuilder which allows for setting
an upgrade handler and wire it into the Http2MultiplexCodec
implementation.
Result:
When using the Http2MultiplexCodec with h2c upgrades the upgrade handler
will get added to the Http2StreamChannel which represents the
half-closed (local) response of stream 1. It is then up to the user to
manage the transition from the IO channel pipeline configuration
necessary for making the h2c upgrade request to a form where it can read
the response from the new stream channel.
Fixes#7947.
Motivation:
Our http2 child channel implementation was not 100 % complete and had a few bugs. Beside this the performance overhead was non-trivial.
Modifications:
There are a lot of modifications, the most important....
* Http2FrameCodec extends Http2ConnectionHandler and Http2MultiplexCodec extends Http2FrameCodec to reduce performance heads and inter-dependencies on handlers in the pipeline
* Correctly handle outbound flow control for child channels
* Support unknow frame types in Http2FrameCodec and Http2MultiplexCodec
* Use a consistent way how to create Http2ConnectionHandler, Http2FrameCodec and Http2MultiplexCodec (via a builder)
* Remove Http2Codec and Http2CodecBuilder as the user should just use Http2MultipleCodec and Http2MultiplexCodecBuilder now
* Smart handling of flushes from child channels to reduce overhead
* Reduce object allocations
* child channels always use the same EventLoop as the parent Channel to reduce overhead and simplify implementation.
* Not extend AbstractChannel for the child channel implementation to reduce overhead in terms of performance and memory usage
* Remove Http2FrameStream.managedState(...) as the user of the child channel api should just use Channel.attr(...)
Result:
Http2MultiplexCodec (and so child channels) and Http2FrameCodec are more correct, faster and more feature complete.
